Composition comprising zuclopenthixol Field of the invention The present invention relates to a pharmaceutical composition comprising zuclopenthixol, or a pharmaceutically acceptable salt thereof, and a cyclodextrin, as well as to preparation of and use of said pharmaceutical composition. Background of the invention Zuclopenthixol is a first-generation antipsychotic drug which is marketed as a medicament and used for treatment of schizophrenia, psychoses, or mania. Zuclopenthixol is marketed since 1976 across the world under tradenames such as cisordinol or clopixol. Zuclopenthixol is a thioxanthene and is the cis-isomer of clopenthixol. It is an antagonist for both dopamine D1 and D2 receptors, α1-adrenoceptors and 5-HT2 receptors with a high affinity, whereas it has no affinity for muscarinic acetylcholine receptors. Zuclopenthixol has a chemical structure according to formula (I) Zuclopenthixol is marketed in different formulations, one of which is an aqueous composition formulation which is used for administration by oral drop comprising the active substance at a concentration of 20 mg/mL and further comprising 12% (w/v) ethanol at pH 2. Other formulations of zuclopenthixol include two different solutions for injection (comprising zuclopenthixol acetate or zuclopenthixol decanoate, respectively), with the decanoate ester formulation being a long-acting formulation (LAI). The inventors of the present inventions have identified that Zuclopenthixol in aqueous compositions is prone to degradation with formation of degradation products wherein e.g. the alkene of zuclopenthixol is either hydrolyzed, partially or fully oxidized, or wherein the stereochemistry of the alkene is converted to the trans-isomer. Thus, as identified by the inventors, there is a need for pharmaceutical formulations of zuclopenthixol wherein the degradation is prevented or decreased, and the stability is high. Summary of the invention The inventors of the present invention have surprisingly found that zuclopenthixol in a formulation comprising 12% (w/v) ethanol at pH 2 is prone to degradation and that the stability of zuclopenthixol is significantly increased in a formulation comprising a cyclodextrin. The inventors have found that zuclopenthixol is capable of forming an inclusion complex with cyclodextrins, such as 2-hydroxypropyl- β-cyclodextrin, and that such inclusion complexes provide protection of specifically the alkene of zuclopenthixol, whereby degradation of zuclopenthixol, such as via alkene hydrolysis or oxidation is prevented or decreased. The formulation of the present disclosure further maintains a low level of isomerization of the double bond. Thus, in one aspect, the present invention relates to a pharmaceutical composition comprising a compound of formula (I) Formula (I), or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable cyclodextrin. In a second aspect, the present invention relates to a pharmaceutical composition as described herein for use in the treatment of a CNS disorder, such as psychosis. In a third aspect, the present invention relates to a method for preparing a pharmaceutical composition as described herein, the method comprising the steps of: a. dissolving the pharmaceutically acceptable cyclodextrin in water, b. adding zuclopenthixol to the composition formed in step a. and stirring until dissolved, and c. adjusting pH of the composition by addition of sodium hydroxide. Description of drawings Figures 1 A-D shows the amounts of degradations products, 2-CTX(A), Sordinol Carbinol(B), Sordinol Dicarbinol(C), and unknown total(D), in formulations at varying pH (2.0, 4.0 or 6.0) and in the presence (H3PO4 or AcOH) or absence (pH) of buffer systems. The % content of the degradation products were analyzed at t=0 and after storage of the formulations for 17 and 36 days. Figures 2 A-D shows the amounts of degradations products, 2-CTX(A), Sordinol Carbinol(B), Sordinol Dicarbinol(C), and unknown total(D), in formulations at pH 4.0 and comprising either AcOH buffer or cyclodextrins (kleptose or captisol). The % content of the degradation products were analyzed at t=0 and after storage of the formulations for 17 and 36 days. Figures 3 A-D shows the amounts of degradations products, 2-CTX(A), Sordinol Carbinol(B), Sordinol Dicarbinol(C), and unknown total(D), in formulations comprising 2-hydroxypropyl-β-cyclodextrin (Kleptose) and at varying pH (3, 4, 5, 6, 7). The % content of the degradation products were analyzed at t=0 and after storage of the formulations for 4 and 19 weeks. Figures 4 A-B shows the absorbance measured at 410 nm (A) and 440 nm (B) for formulations comprising 2-hydroxypropyl-β-cyclodextrin (Kleptose) and at varying pH (3, 4, 5, 6, 7). The absorbance was measured at t=0 and after storage of the formulations for 2, 4, and 19 weeks. Figures 5 A-D shows the amounts of degradations products, 2-CTX(A), Sordinol Carbinol(B), Sordinol Dicarbinol(C), and unknown total(D), in formulations comprising Sulfobutylether-β-cyclodextrin Sodium (Captisol) and at varying pH (2, 4, 6). The % content of the degradation products were analyzed at t=0 and after storage of the formulations for 17 and 36 days. Figure 6 shows the amounts of degradations products, 2-CTX, Sordinol Carbinol, Sordinol Dicarbinol, and Trans(E)-clopenthixol, in formulations comprising zuclopenthixol at pH 2 (dark grey), or comprising zuclopenthixol and 2-hydroxypropyl-β-cyclodextrin (Kleptose) at pH 5 (middle grey) or pH 6 (light grey). The % content of the degradation products were analyzed after 12 weeks (pH2 formulation without cyclodextrin) or after 19 weeks (cyclodextrin containing formulations) of storage at 40 °C/75%RH. Detailed description of the invention The present invention relates to a formulation of zuclopenthixol, wherein degradation of the compound is prevented or decreased, and thus, wherein the stability of zuclopenthixol is increased. As demonstrated by the present disclosure, the stability of zuclopenthixol is increased in a formulation comprising a cyclodextrin, such as comprising 2-hydroxypropyl-β-cyclodextrin, whereby degradation of zuclopenthixol, such as via alkene hydrolysis or oxidation is prevented or decreased. The formulation of the present disclosure also demonstrates a low propensity to isomerization of the alkene of zuclopenthixol upon storage. Thus, the present invention relates to a pharmaceutical formulation comprising a compound of formula (I) Formula (I), or a pharmaceutically acceptable salt thereof, which compound is also referred to herein as zuclopenthixol. In one embodiment, the present disclosure provides a pharmaceutical formulation comprising zuclopenthixol, or a pharmaceutically acceptable salt thereof, and 2-hydroxypropyl-β-cyclodextrin. In aqueous solutions, zuclopenthixol is prone to degradation with formation of degradation products. Examples of degradation products of zuclopenthixol include compounds wherein the alkene of zuclopenthixol is either hydrolyzed, partially or fully oxidized, or wherein the stereochemistry of the alkene is converted from the cis-isomer to the trans-isomer. Thus, in one embodiment, the pharmaceutical composition of the present disclosure provides an increased stability of zuclopenthixol. Examples of degradation products of zuclopenthixol include but are not limited to compounds of formula (II), (III), (IV) and (V). In one embodiment, the pharmaceutical composition of the present disclosure prevents or decreases degradation of zuclopenthixol to the compound of formula (II) formula (II), which is also referred to herein as sordinol carbinol or carbinol. In one embodiment, the compound of formula (II) is formed by hydrolysis of zuclopenthixol. In one embodiment, the pharmaceutical composition of the present disclosure prevents or decreases degradation of zuclopenthixol to the compound of formula (III) formula (III), which is also referred to herein as sordinol dicarbinol or dicarbinol. In one embodiment, the pharmaceutical composition of the present disclosure prevents or decreases degradation of zuclopenthixol to the compound of formula (IV) formula (IV), which is also referred to herein as 2-CTX. In one embodiment, the pharmaceutical composition of the present disclosure provides a low level of degradation of zuclopenthixol to the compound of formula (V) formula (V), which is also referred to herein as trans-ordinol or trans(E)- clopenthixol. Degradation of zuclopenthixol to form trans-clopenthixol may be a result of light exposure of the formulation. In one embodiment, the pharmaceutical composition of the present disclosure prevents or decreases degradation of zuclopenthixol, such as prevents or decreases degradation of zuclopenthixol to any one of the compounds of formula (II), (III), and (IV), or any combination of the compounds of formula (II), (III), and (IV). The pharmaceutical composition of the present disclosure provides such decreased degradation of zuclopenthixol by formation of a complex of zuclopenthixol with the pharmaceutically acceptable cyclodextrin in the composition, such as by formation of an inclusion complex, whereby the alkene of zuclopenthixol is protected from degradation, such as protected from hydrolysis and/or from oxidative degradation. In one embodiment, the pharmaceutical composition provides a low level of isomerization, such as provides a low level of conversion of the cis-alkene to the trans-alkene. Cyclodextrin Cyclodextrins are a family of cyclic oligosaccharides, consisting of a macrocyclic ring of glucose subunits. Cyclodextrins are composed of 5 or more α-D-glucopyranoside units linked by α-1,4 glycosidic bonds. Typical cyclodextrins contain a number of glucose monomers ranging from six to eight units in a ring, creating a cone shape. α (alpha)-cyclodextrins contain 6 glucose subunits, β (beta)- cyclodextrins contain 7 glucose subunits, and γ (gamma)-cyclodextrins contain 8 glucose subunits in the ring. Cyclodextrins have a toroidal shape, with the larger and the smaller openings of the toroid exposing to the solvent secondary and primary hydroxyl groups respectively. Because of this arrangement, the interior of the cyclodextrin toroid is less hydrophilic than the aqueous environment and thus able to host e.g. hydrophobic molecules by formation of an inclusion complex. In contrast, the exterior of the cyclodextrin toroid is sufficiently hydrophilic to impart cyclodextrins (or their inclusion complexes) water solubility. Inclusion complex formation, however, does not take place with any compound, and an inclusion complex may form only if the compound has e.g. the required physicochemical properties and size, and if the correct match between cyclodextrin or cyclodextrin derivative and compound is found, with the correct properties of the solution. Often complex formation requires addition of heat to drive the complex formation. Given the potential of cyclodextrins to form inclusion complexes, these have been used for increasing the solubility of hydrophobic molecules. Formation of inclusion complexes between a cyclodextrin and a molecule has also been used for masking of odour and/or taste of the molecule. Formation of inclusion complexes between a cyclodextrin and a molecule may also confer protection of the molecule from the exterior environment of the solution. However, the ability of cyclodextrins to stabilize a given molecule cannot be predicted and as described above, not all molecules are capable of forming such inclusion complexes. Formation of the inclusion complex is a dynamic process, wherein the equilibrium of the inclusion complex depends on various factors such as the type of CD, pH of the medium, and the presence of any additives. Furthermore, depending on the equilibrium of the inclusion complex, at any given time, some molecules in the solution will be associated with the cyclodextrin whereas others will be freely flowing in the solution. Only the molecules associated with the cyclodextrin will be protected from degradation, whereas the freely flowing molecules will be subjected to the external environment of the solution. Finally, protection is conferred only if the inclusion complex between the cyclodextrin and the molecule is formed at the site of the molecule prone to degradation. Thus, many parameters need to be fulfilled before a protective effect of cyclodextrins is obtained, resulting in said potential protecting effect being difficult to predict or control. In the present invention, the inventors have surprisingly found that zuclopenthixol is capable of forming a complex with cyclodextrins, such as capable of forming an inclusion complex with a cyclodextrin, such as 2-hydroxypropyl-β-cyclodextrin, and that such complex provides protection of zuclopenthixol from degradation. More specifically it has been found that the complex provides protection of the alkene of zuclopenthixol from degradation such as hydrolysis and/or oxidative degradation. Furthermore, a low amount of conversion of the cis-alkene to the trans-alkene was observed for the pharmaceutical composition of the present disclosure. The term ‘pharmaceutically acceptable cyclodextrin’, as used herein, refers to a cyclodextrin which is physiologically tolerable and thus safe to include in a pharmaceutical formulation, such as cyclodextrins causing no known adverse events when administered to a mammal, such as a human. A pharmaceutically acceptable cyclodextrins may also for example be a cyclodextrin approved by the regulatory authorities or listed in generally recognized pharmacopeia, such as the U.S. pharmacopeia, for use in mammals, more particularly in humans. Examples of pharmaceutically acceptable cyclodextrins include but are not limited to randomly methylated β-cyclodextrin, 2-O-methyl-β- cyclodextrin, heptakis-(2,6-di-O-methyl)-β-cyclodextrin, (dimethyl-β-cyclodextrin), acetylated dimethyl-β-cyclodextrin, heptakis-(2,3,6-tri-O-methyl)-β-cycIodextrin, trimethyl-β-cyclodextrin, 2- hydroxypropyl-β-cyclodextrin, β-cyclodextrin sulphate, β-cyclodextrin phosphate, and 2- hydroxypropyl-gamma-cyclodextrin. In one embodiment, the pharmaceutically acceptable cyclodextrin is selected from the group consisting of randomly methylated β-cyclodextrin, 2-O-methyl-β-cyclodextrin, heptakis-(2,6-di-O- methyl)-β-cyclodextrin, (dimethyl-β-cyclodextrin), acetylated dimethyl-β-cyclodextrin, heptakis- (2,3,6-tri-O-methyl)-β-cycIodextrin, trimethyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin, β- cyclodextrin sulphate, β-cyclodextrin phosphate, and 2-hydroxypropyl-gamma-cyclodextrin. In a preferred embodiment, the pharmaceutically acceptable cyclodextrin is 2-hydroxypropyl-β- cyclodextrin (also referred to herein as 2-HP-β-CD). Cyclodextrins may be substituted, derivatized or modified to varying degrees, which may be indicated by the degree of substitution (DS). DS indicates the average number of substituted hydroxyl groups per anhydroglucose unit of the cyclodextrin. An example of suitable DS of the 2-hydroxypropyl-β- cyclodextrin of the present invention include amorphous, randomly substituted 2-hydroxypropyl-β- cyclodextrin having a DS in the range of 0.4 to 1.2, such as in the range of 0.4 to 1.0, such as in the range of 0.4 to 0.7, such as in the range of 0.5 to 0.7, such as in the range of 0.6 to 0.7. In one embodiment, the DS of the 2-hydroxypropyl-β-cyclodextrin is at least 0.5, such as at least 0.6, for example 0.62. Examples of suitable 2-hydroxypropyl-β-cyclodextrin is Kleptose, such as Kleptose having a degree of substitution of about 0.6, such as about 0.62. The degree of substitution may be determined by methods known by the skilled person, such as by e.g. gas chromatography (GC), nuclear magnetic resonance (NMR), and plasma desorption fast atom bombardment mass spectrometry (FAB-MS). In one embodiment, the pharmaceutical composition of the present invention comprises a complex formed between zuclopenthixol and the cyclodextrin, such as an inclusion complex formed between zuclopenthixol and the cyclodextrin. In one embodiment, the complex or inclusion complex has an equilibrium constant K of at least 700 M ^-1 . In one embodiment, the equilibrium constant is at least 700 M ^-1 when measured at pH 4. The equilibrium constant may be measured according to the method as described in example 5 of the present disclosure or by other methods known to the person skilled in the art. Pharmaceutical composition The present invention relates to a pharmaceutical composition comprising a compound of formula (I) Formula (I), or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable cyclodextrin. In one embodiment, the pharmaceutical composition is an aqueous liquid composition, such as an oral drop formulation. In one embodiment, the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 1 mg/mL to about 75 mg/mL, such as in the range of about 1 mg/mL to about 50 mg/mL, such as in the range of about 1 mg/mL to about 40 mg/mL, such as in the range of about 1 mg/mL to about 30 mg/mL, such as in the range of about 1 mg/mL to about 25 mg/mL, such as in the range of about 1 mg/mL to about 20 mg/mL. In one embodiment, the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 5 mg/mL to about 100 mg/mL, such as in the range of about 10 mg/mL to about 100 mg/mL, such as in the range of about 15 mg/mL to about 100 mg/mL, such as in the range of about 16 mg/mL to about 100 mg/mL, such as in the range of about 18 mg/mL to about 100 mg/mL, such as in the range of about 20 mg/mL to about 100 mg/mL. In one embodiment, the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 5 mg/mL to about 75 mg/mL, such as in the range of about 10 mg/mL to about 50 mg/mL, such as in the range of about 10 mg/mL to about 40 mg/mL, such as in the range of about 10 mg/mL to about 30 mg/mL, such as in the range of about 15 mg/mL to about 25 mg/mL, such as in the range of about 18 mg/mL to about 22 mg/mL. In a preferred embodiment, the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is about 20 mg/mL. In one embodiment, the compound of formula (I) is in the form of a salt, such as a hydrochloride salt, hydrobromide salt, dihydrobromide salt, or dihydrochloride salt. In a preferred embodiment the compound of formula (I) is in the form of a dihydrochloride salt. In one embodiment, the molar ratio of the cyclodextrin to the compound of formula (I) is in the range of about 0.1:1 to about 100:1, such as in the range of about 0.5:1 to about 100:1, such as in the range of about 1:1 to about 100:1, such as in the range of about 2:1 to about 100:1, such as in the range of about 5:1 to about 100:1. In one embodiment, the molar ratio of the cyclodextrin to the compound of formula (I) is in the range of about 0.1:1 to about 100:1, such as in the range of about 0.5:1 to about 50:1, such as in the range of about 0.5:1 to about 20:1, such as in the range of about 0.5:1 to about 10:1, such as in the range of about 0.8:1 to about 5:1, such as in the range of about 0.8:1 to about 2:1, such as in the range of about 0.9:1 to about 1.5:1. In a preferred embodiment, the molar ratio of the cyclodextrin to the compound of formula (I) is about 1:1. In one embodiment, the composition comprises 2-hydroxypropyl-β-cyclodextrin in an amount above the stoichiometric amount as compared to zuclopenthixol, such as having a molar ratio of the cyclodextrin to the compound of formula (I) of about 1.5:1, about 1.4:1, about 1.3:1, about 1.2:1, about 1.1:1, or about 1.05:1. Such slight excess of cyclodextrin may be advantageous to ensure full protection of the zuclopenthixol. In one embodiment, the cyclodextrin is present in an amount from about 5% to about 20% (w/v), such as in an amount from about 5% to about 15% (w/v), such as in an amount from about 5% to about 12% (w/v), preferably the cyclodextrin is present in an amount from about 5% to about 10% (w/v). In one embodiment, the cyclodextrin is present in an amount of at least 12% (w/v), preferably in an amount of at least 10% (w/v). In one embodiment, the cyclodextrin is present in an amount of about 15% (w/v), about 14% (w/v), about 13% (w/v), about 12% (w/v), about 11% (w/v), about 10% (w/v), about 9% (w/v), or about 8% (w/v). In one embodiment, the pH of the composition is above 3 and below 7, such as in the range of 4-6, such as in the range of 5-6, for example 5, for example 6. In a preferred embodiment, the pH of the composition is about 5, such as 5. In one embodiment, the pH of the composition is in the range of 4 to 7, such as in the range of 4 to 6, such as in the range of 4.5 to 6.5, such as in the range of 4.8 to 5.2, such as in the range of 4.5 to 5.5, such as in the range of 5 to 6, preferably the pH is about 5, such as 5. The pH of the composition may be adjusted by addition of sodium hydroxide (NaOH) to the composition after dissolving zuclopenthixol and the cyclodextrin in the aqueous solution. In one embodiment, no additional buffering agent is needed for maintaining a stable pH during storage, since zuclopenthixol may function as a buffering agent in the composition. Thus, in one embodiment, the composition does not contain an additional buffering agent. The pharmaceutical composition of the present invention may further comprise ethanol (EtOH). The presence of ethanol in the composition may prevent bacterial growth in the composition during storage. Thus, in one embodiment, the pharmaceutical composition further comprises ethanol. In one embodiment, the ethanol content of the pharmaceutical composition is in the range of 0 % to 20 (w/v), such as in the range of 0 % to 15 (w/v), such as in the range of 5 % to 15 (w/v). In a preferred embodiment, the ethanol content of the pharmaceutical composition is about 12% (w/v). The pharmaceutical composition of the present disclosure may be used as an oral drop formulation, whereby zuclopenthixol as the active pharmaceutical ingredient (API) of the composition is administered by oral drop. For such administration, it is of high importance that the viscosity of the composition is correct and stable during storage, and that the size of the drops and the amount of API in each drop is consistent during storage. The implications of viscosity, drop size and amount of API in each drop, further complicates the development of a pharmaceutical formulation of zuclopenthixol which is suitable for use as an oral drop formulation. The inventors of the present disclosure have found that a pharmaceutical composition of zuclopenthixol comprising a cyclodextrin is suitable for use as an oral drop formulation. Thus, in one embodiment, the present invention provides a pharmaceutical composition for use as an oral drop formulation comprising a compound of formula (I) Formula (I), or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable cyclodextrin. In one embodiment, the pharmaceutical composition of the present disclosure is an oral drop formulation. In one embodiment, the pharmaceutical composition of the present disclosure is stable during storage, such as provides a stable drop measure, stable drop rate, and stable uniformity of dose during storage. In a specific embodiment, the pharmaceutical composition of the present disclosure comprises a compound according to formula (I), or a pharmaceutically acceptable salt thereof, 2-hydroxypropyl-β- cyclodextrin and ethanol, wherein a. the concentration of the compound of formula (I) is in the range of 15 to 25 mg/mL, preferably 20 mg/mL; b. the concentration of 2-hydroxypropyl-β-cyclodextrin is present in an amount from about 5% to about 12% (w/v), preferably 10% (w/v); c. the ethanol content is in the range of 5% to 15% (w/v), preferably 12% (w/v); and d. the pH is in the range of 4.5 to 5.5, preferably 5. In a further embodiment, the pharmaceutical composition of the present disclosure comprises zuclopenthixol dihydrochloride, 2-hydroxypropyl-β-cyclodextrin and ethanol, wherein a. the concentration of zuclopenthixol dihydrochloride is in the range of 15 to 25 mg/mL, preferably about 23.6 mg/mL; b. the concentration of 2-hydroxypropyl-β-cyclodextrin is present in an amount from about 5% to about 12% (w/v), preferably 10% (w/v); c. the ethanol content is in the range of 5% to 15% (w/v), preferably 12% (w/v); and d. the pH is in the range of 4.5 to 5.5, preferably 5. Method of preparing composition Complex formation between zuclopenthixol and the pharmaceutically acceptable cyclodextrin, such as 2-hydroxypropyl-β-cyclodextrin, takes place spontaneously in an aqueous solution at room temperature. This is in contrast to other cyclodextrin complexes known in the art where complex formation requires application of heat. Hence, preparation of the pharmaceutical composition of the present invention is fast and cost-efficient with a limited number of operational steps during the process. Thus, in one aspect, the present invention provides a method of preparing a pharmaceutical composition as disclosed herein, the method comprising the steps of: a. dissolving the pharmaceutically acceptable cyclodextrin in water, b. adding zuclopenthixol to the composition formed in step a. and stirring until dissolved, and c. adjusting pH of the composition by addition of sodium hydroxide. In one embodiment, step b. comprises stirring for less than 1 h, such as for less than 50 min, 40min, 30, or 20 min. In one embodiment, the method further comprises an additional step of addition of ethanol to the composition formed in step a. prior to addition of zuclopenthixol. In one embodiment, pH is adjusted by addition of sodium hydroxide, such as 5N sodium hydroxide, under vigorous stirring of the composition. In one embodiment, the method further comprises a step d. of addition of water to obtain the desired concentration of zuclopenthixol in the composition, such as obtaining a concentration of about 20 mg/mL of zuclopenthixol. In one embodiment, the composition is protected from light during the method of preparation. Stability of composition The pharmaceutical composition of the present invention provides a high stability formulation of zuclopenthixol, displaying an amount of degradation products which is well within and below the specification limits of the zuclopenthixol formulation. Furthermore, the pharmaceutical composition of the present invention displays a very stable color of solution, also falling within the specification of the zuclopenthixol formulation. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 1 w/w% of the carbinol degradation product (formula II) after storage for 24 months at 25 °C. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.1%w/w, such as less than 0.05 %w/w of the carbinol degradation product (formula II) after storage for 18 months at 25°C/60% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.5 w/w%, such as less than 0.1 w/w%, such as less than 0.05 w/w%, such as less than 0.02 w/w% of the carbinol degradation product (formula II) after 6 months of storage at 40°C/75% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 1 w/w% of the dicarbinol degradation product (formula III) after storage for 24 months at 25 °C. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.1%w/w, such as less than 0.05 %w/w of the dicarbinol degradation product (formula III) after storage for 18 months at 25°C/60% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.5 w/w%, such as less than 0.2 w/w%, such as less than 0.1 w/w% of the dicarbinol degradation product (formula III) after 6 months of storage at 40°C/75% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.2 w/w% of the 2-CTX degradation product (formula IV) after storage for 24 months at 25 °C. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.1%w/w, such as less than 0.05 %w/w of the 2-CTX degradation product (formula IV) after storage for 18 months at 25°C/60% RH. In one embodiment, the present invention provides a pharmaceutical composition wherein less than less than 0.2 w/w%, such as less than 0.1 w/w%, such as less than 0.05 w/w% of the 2-CTX degradation product (formula IV) after 6 months of storage at 40°C/75% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 2 w/w% of the trans(E)-clopenthixol degradation product (formula V) after storage for 24 months at 25 °C. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.2%w/w, such as less than 0.1 %w/w of the trans(E)-clopenthixol degradation product (formula V) after storage for 18 months at 25°C/60% RH. In one embodiment, the present invention provides a pharmaceutical composition wherein less than less than 1 w/w%, such as less than 0.5 w/w%, such as less than 0.2 w/w% of the trans(E)-clopenthixol degradation product (formula V) after 6 months of storage at 40°C/75% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.25 w/w% of unknown degradation products after storage for 24 months at 25 °C. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.1%w/w, such as less than 0.05 %w/w of unknown degradation products after storage for 18 months at 25°C/60% RH. In one embodiment, the pharmaceutical composition as disclosed herein comprises less than 0.2 w/w%, such as less than 0.1 w/w%, such as less than 0.05 w/w%, of unknown degradation products after 6 months of storage at 40°C/75% RH. In one embodiment, the color of solution of the pharmaceutical composition of the present invention is equal to or less than GY5, such as equal to or less than GY6, such as less than equal to or less than GY7 after storage for 24 months at 25 °C. In one embodiment, the color of solution of the pharmaceutical composition of the present invention is equal to or less than GY5, such as equal to or less than GY6, such as less than equal to or less than GY7 after storage for 18 months at 25°C/60% RH. In one embodiment, the color of solution of the pharmaceutical composition of the present invention is equal to or less GY7 after 6 months of storage at 40°C/75% RH. GY, as used herein, refers to the color of the formulation, as compared to standard solution as described in European Pharmacopoeia Chapter 2.2.2 (10 ^th edition). The pharmaceutical composition of the present invention may be stored in any suitable container, such as a glass container or a suitable plastic container, such as polypropylene or polyethylene. In one embodiment, the pharmaceutical composition is stored in a Type III glass bottle. Method of treatment by administering composition The pharmaceutical composition of the present invention comprising zuclopenthixol may be used in treatment of a CNS disorder, such as for example in the treatment of schizophrenia, psychoses, or mania. In one embodiment, said CNS disorder is acute or chronic. In one embodiment, the CNS disorder is acute psychosis, such as in a patient suffering from schizophrenia or mania. In one embodiment, the CNS disorder is acute schizophrenia, acute psychosis, or mania. In one embodiment, the CNS disorder is chronic schizophrenia or other psychoses. In one embodiment, the CNS disorder is acute and chronic schizophrenia or other psychoses, especially with symptoms such as hallucinations, delusions, thought disturbances as well as agitation, restlessness, hostility and/or aggressiveness. Thus, in one aspect, the present invention provides a pharmaceutical composition according to the present disclosure for use in the treatment of a CNS disorder. In one embodiment, the present invention provides a method of treatment of a CNS disorder, the method comprising administration of a pharmaceutical composition according to the present disclosure. In one embodiment, the present invention provides use of a pharmaceutical composition according to the present disclosure for the manufacture of a medicament for use in the treatment of a CNS disorder. In one embodiment, the present invention provides use of a pharmaceutical composition according to the present disclosure for the treatment of a CNS disorder. In one embodiment, the CNS disorder is psychosis. In one embodiment, the patient being treated for psychosis is suffering from schizophrenia or mania. In one embodiment, the pharmaceutical composition according to the present invention is administered orally, such as by oral drop. Items 1. A pharmaceutical composition comprising a compound of formula (I) Formula (I), or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable cyclodextrin. 2. The pharmaceutical composition according to item 1, wherein the composition is an aqueous liquid composition. 3. The pharmaceutical composition according to any one of the preceding items, wherein the pharmaceutically acceptable cyclodextrin is selected from pharmaceutically acceptable, water- soluble, native or derivatized cyclodextrins, such as selected from the group consisting of randomly methylated β-cyclodextrin, 2-O-methyl-β-cyclodextrin, heptakis-(2,6-di-O-methyl)-β- cyclodextrin, (dimethyl-β-cyclodextrin), acetylated dimethyl-β-cyclodextrin, heptakis-(2,3,6-tri- O-methyl)-β-cycIodextrin, trimethyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin, β- cyclodextrin sulphate, β-cyclodextrin phosphate, and 2-hydroxypropyl-gamma-cyclodextrin. 4. The pharmaceutical composition according to any one of the preceding items, wherein the pharmaceutically acceptable cyclodextrin is 2-hydroxypropyl-β-cyclodextrin. 5. The pharmaceutical composition according to any one of the preceding items, wherein the pharmaceutically acceptable cyclodextrin is 2-hydroxypropyl-β-cyclodextrin having a degree of substitution of at least 0.6, such as at least 0.62. 6. The pharmaceutical composition according to any one of the preceding items, wherein the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 1 mg/mL to about 75 mg/mL, such as in the range of about 1 mg/mL to about 50 mg/mL, such as in the range of about 1 mg/mL to about 40 mg/mL, such as in the range of about 1 mg/mL to about 30 mg/mL, such as in the range of about 1 mg/mL to about 25 mg/mL, such as in the range of about 1 mg/mL to about 20 mg/mL. 7. The pharmaceutical composition according to any one of the preceding items, wherein the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 5 mg/mL to about 100 mg/mL, such as in the range of about 10 mg/mL to about 100 mg/mL, such as in the range of about 15 mg/mL to about 100 mg/mL, such as in the range of about 16 mg/mL to about 100 mg/mL, such as in the range of about 18 mg/mL to about 100 mg/mL, such as in the range of about 20 mg/mL to about 100 mg/mL. 8. The pharmaceutical composition according to any one of the preceding items, wherein the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is in the range from about 1 mg/mL to about 100 mg/mL, such as in the range of about 5 mg/mL to about 75 mg/mL, such as in the range of about 10 mg/mL to about 50 mg/mL, such as in the range of about 10 mg/mL to about 40 mg/mL, such as in the range of about 10 mg/mL to about 30 mg/mL, such as in the range of about 15 mg/mL to about 25 mg/mL, such as in the range of about 18 mg/mL to about 22 mg/mL, preferably the concentration of the compound of formula (I) or a pharmaceutically acceptable salt thereof is about 20 mg/mL. 9. The pharmaceutical composition according to any one of the preceding items, wherein the compound of formula (I) is in the form of a salt, such as a hydrochloride salt, hydrobromide salt, dihydrobromide salt, or dihydrochloride salt. 10. The pharmaceutical composition according to any one of the preceding items, wherein the molar ratio of the cyclodextrin to the compound of formula (I) is in the range of about 0.1:1 to about 100:1, such as in the range of about 0.5:1 to about 100:1, such as in the range of about 1:1 to about 100:1, such as in the range of about 2:1 to about 100:1, such as in the range of about 5:1 to about 100:1. 11. The pharmaceutical composition according to any one of the preceding items, wherein the molar ratio of the cyclodextrin to the compound of formula (I) is in the range of about 0.1:1 to about 100:1, such as in the range of about 0.5:1 to about 50:1, such as in the range of about 0.5:1 to about 20:1, such as in the range of about 0.5:1 to about 10:1, such as in the range of about 0.8:1 to about 5:1, such as in the range of about 0.8:1 to about 2:1, such as in the range of about 0.9:1 to about 1.5:1, preferably the molar ratio of the cyclodextrin to the compound of formula (I) is about 1:1. 12. The pharmaceutical composition according to any one of the preceding items, wherein the cyclodextrin is present in an amount from about 5% to about 20% (w/v), such as in an amount from about 5% to about 15% (w/v), such as in an amount from about 5% to about 12% (w/v), preferably the cyclodextrin is present in an amount from about 5% to about 10% (w/v). 13. The pharmaceutical composition according to any one of the preceding items, wherein the cyclodextrin is present in an amount of at least 12% (w/v), such as at least 11% (w/v), preferably at least 10% (w/v). 14. The pharmaceutical composition according to any one of the preceding items, wherein the pH of the composition is above 3 and below 7, such as in the range of 4-6, such as in the range of 5-6, for example 5, for example 6, preferably 5. 15. The pharmaceutical composition according to any one of the preceding items, wherein the pH of the composition is in the range of 4 to 7, such as in the range of 4 to 6, such as in the range of 4.5 to 6.5, such as in the range of 4.8 to 5.2, such as in the range of 4.5 to 5.5, such as in the range of 5 to 6, preferably the pH is 5. 16. The pharmaceutical composition according to any one of the preceding items, wherein the composition further comprises EtOH. 17. The pharmaceutical composition according to any one of the preceding items, wherein the EtOH content is in the range of 0 % to 20 (w/v), such as in the range of 0 % to 15 (w/v), such as in the range of 5 % to 15 (w/v), preferably the ethanol content is 12% (w/v). 18. The pharmaceutical composition according to any one of the preceding items, wherein the composition does not contain a buffer. 19. The pharmaceutical composition according to any one of the preceding items, wherein the composition is an oral drop formulation. 20. A pharmaceutical composition comprising a compound according to formula (I), or a pharmaceutically acceptable salt thereof, 2-hydroxypropyl-β-cyclodextrin and ethanol, wherein a. the concentration of the compound of formula (I) is in the range of 15 to 25 mg/mL, preferably 20 mg/mL, b. the concentration of 2-O-hydroxypropyl-β-cyclodextrin is present in an amount from about 5% to about 12% (w/v), preferably 10 % (w/v). c. the ethanol content is in the range of 5% to 15% (w/v), preferably 12% (w/v), and d. the pH is in the range of 4.5 to 5.5, preferably 5. 21. The pharmaceutical composition according to any one of items 1 to 20 for use in the treatment of a CNS disorder. 22. The pharmaceutical composition for use according to item 21, wherein the CNS disorder is selected from the group consisting of schizophrenia, psychoses, or mania. 23. The pharmaceutical composition for use according to any one of items 21 to 22, wherein the composition is administered orally, such as by oral drop. 24. A method of preparing a pharmaceutical composition according to any one of items 1 to 20, the method comprising the steps of: a. dissolving the pharmaceutically acceptable cyclodextrin in water, b. adding zuclopenthixol to the composition formed in step a. and stirring until dissolved, and c. adjusting pH of the composition by addition of sodium hydroxide. Examples Example 1: General method for preparation of zuclopenthixol pharmaceutical composition The pharmaceutical composition of the present invention may be prepared as outlined in the present example. To a 3000 mL measuring flask was added 2-hydroxypropyl-β-cyclodextrin (300 g) and approximately 70% of the purified water (2100 mL). The mixture was stirred until the cyclodextrin was dissolved, approximately 10 min. Ethanol (360 g) was added with stirring, followed by addition of zuclopenthixol 2HCl (70.92 g) and stirring until dissolved, approximately 1 h. The solution was protected from light using aluminum foil. The pH of the solution was adjusted to pH 5.0 by addition of 1N sodium hydroxide (appr.150 mL) with continuous stirring before the measuring flask was filled with purified water to a total volume of 3000 mL. The solution was filtered using a 0.45 µm filter and the pH of the solution was measured again. Example 2: Stabilizing formulation – Screening for stabilizing factors The aim of this examples was to investigate different factors for their ability to stabilize Zuclopenthixol in the formulation and to prevent degradation of zuclopenthixol in the formulation, such as prevent degradation by hydrolysis and/or oxidative degradation as described above. In the example, it was tested whether variation of pH, addition of buffer systems, or addition of cyclodextrins would facilitate the desired stabilization and prevent degradation. Materials and methods: The influence of different parameters on Zuclopenthixol stability and degradation was studied by preparation of different formulations 1-10, table 1: Table 1: Overview of formulations tested Preparation of samples: The test formulations were prepared in a batch size of 125 mL, as described below for each formulation. In general, a fresh bottle of ethanol was used in order to decrease the risk of peroxide content in ethanol thereby lowering the risk of oxidation due to peroxide content. After end preparation the formulations were gassed with sterile filtered argon for 3 minutes. All formulations were prepared with protection from light. The solutions were stored in suitable utensil (also referred to as contained) prior to transfer of suitable volume for stability study, see further below. Formulation 1: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl and 70 mL ELGA water. pH measured to 2.0 with no addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 2: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl and 70 mL ELGA water. pH was adjusted to 4.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 3: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl and 70 mL ELGA water. pH was adjusted to 6.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 4: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl, 70 mL ELGA water, and 750 µL glacial acetic acid. pH was adjusted to 4.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 5: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl, 70 mL ELGA water, and 750 µL glacial acetic acid. pH was adjusted to 6.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 6: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl, 70 mL ELGA water, and 630 µL phosphoric acid. pH was adjusted to 2.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 7: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl, 70 mL ELGA water, and 630 µL phosphoric acid. pH was adjusted to 6.0 by addition of 5 M NaOH. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 8: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl and 70 mL ELGA water. pH was adjusted to 4.0 by addition of 5 M NaOH. Finally, 12.5 g 2-hydroxypropyl-β-cyclodextrin (Kleptose, degree of substitution of 0.62) was added to the solution with stirring. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 9: To a 100 ml volumetric flask was added 2.9 g Zuclopenthixol 2HCl and 70 mL ELGA water. pH was adjusted to 4.0 by addition of 5 M NaOH. Finally, 12.5 g sulfobutylether-β-cyclodextrin Sodium (Captisol, degree of substitution of 0.94) was added to the solution with stirring. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 10: Due to low solubility of β-CD, formulation 10 was discarded prior to the stability study. Stability study: 10 mL of each of the test formulations prepared according to the above method was transferred to laboratory glassware bottles which were sealed and stored at 40 °C, 75%RH for 4 weeks with protection from light throughout the experiment. Samples were withdrawn after 0, 17 and 36 days and analyzed according to the methods below. pH of the withdrawn samples was measured using a Metrohm 780 pH meter. Amount of degradation products: To measure the content of degradation products, the withdrawn samples were analyzed by HPLC, using a Symmetry Shield RP18, 50 x 2.1 mm ID, 3.5 μm column, mobile phases A: 0.04% TFA in water, B: 0.04% TFA in MeCN, C: methanol. The flow was 0.6 ml/min with a temperature of 40 °C. The injection volume was 10 µL and detection was UV at 270 nm. The gradient was linear with the points 0 min: 82% A, 18% B, 0% C to 8 min: 82% A, 18% B, 0% C to 17 min: 5% A, 10% B, 85% C to 19 min: 5% A, 10% B, 85% C to 30 min: 82% A, 18% B, 0% C. Results: Effect of pH on the stability of zuclopenthixol The results obtained at pH 2.0, 4.0 and 6.0 (figures 1 A-D) show that the stability of zuclopenthixol is higher at a higher pH. The amount of degradation products arising from hydrolysis or oxidative degradation is lower at pH 6 than at pH 2 or 4 (Figures 1 A-C). It was, however, found that the composition at pH 6.0 changed color to a yellowish color within about 1 hour following preparation. Overall impact of addition of buffer system The intention of including a buffer system in the formulation was to stabilize pH with less variation of pH in the formulation over time, and to test whether such stabilization of the pH would have an impact on the stability of zuclopenthixol. In general, addition of acetate buffer at pH 4.0 seemed to decrease the amount of degradation products (Figures 1 A-D). However, the effect was not significant at pH 6.0. Addition of phosphoric acid was found to have no effect on the stability of zuclopenthixol. At pH 2.0 H3PO4 the amount of degradation products was equal to or higher than for the pH 2.0 formulations without buffer. At pH 6.0 H3PO4, the amount of oxidation degradation products was higher than for the pH 6.0 unbuffered formulation. The pH of the formulations was measured after 5 weeks to see the effect of the buffer systems on the variation of pH in the formulation over time. Table 2: variation of pH from t=0 to after 5 weeks of stability test The data in table 2 show that addition of a buffer system may result in a better stabilization of pH at pH 4.0 and 6.0 over a period of 5 weeks. However, as seen from the zuclopenthixol degradation described above in the present example, the lower variation of pH in the formulation over time was not found to have a positive impact on the stability of zuclopenthixol. Effect of cyclodextrins on stability of zuclopenthixol 2-Hydroxypropyl-β-cyclodextrin (Kleptose) The results demonstrate that the presence of 2-hydroxypropyl-β-cyclodextrin (Kleptose) in the formulation results in lower hydrolysis and oxidative degradation of zuclopenthixol (Figures 2 A-C), the same applies to the amount of unknown degradation products (Figure 2D). The observed increased stability of zuclopenthixol in a formulation comprising 2-hydroxypropyl-β- cyclodextrin may be a result of formation of an inclusion complex between zuclopenthixol and 2- hydroxypropyl-β-cyclodextrin. Sulfobutylether-β-cyclodextrin Sodium (Captisol) Addition of sulfobutylether-β-cyclodextrin Sodium (Captisol) to the formulation was found to have no or limited effect on the stability of zuclopenthixol (Figures 2 A-D) One explanation may be that zuclopenthixol is not capable of forming an inclusion complex with sulfobutylether-β-cyclodextrin Sodium (Captisol), although other reasons for the limited effect may exist. Degradation products Carbinol Hydrolysis of zuclopenthixol result in formation of the degradation product carbinol, Formula (II). The results show that formulations having a low pH of 2.0, with or without phosphoric acid buffer resulted in a high content of carbinol. The remaining formulations showed a lower content of carbinol (Figure 1B). The results suggest that the double bond of zuclopenthixol is more prone to hydrolysis at lower pH. Table 3 displays the amount of carbinol in the different formulations of the example. Table 3: amount of carbinol in the formulations at t=0, and after 17 and 36 days. Dicarbinol The results show that addition of Sulfobutylether-β-cyclodextrin Sodium (Captisol) result in a higher amount of dicarbinol degradation product (Formula (III)) (Figure 2C). The degradation product is also formed in higher amount at lower pH (Figure 1C). In contrast, the results show that the present of 2-hydroxypropyl-β-cyclodextrin in the formulation results in a low amount of dicarbinol of 0.054% at t=36h (Figure 2C). Table 4 displays the amount of dicarbinol in the different formulations of the example. Table 4: amount of dicarbinol in the formulations at t=0, and after 17 and 36 days. 2-CTX The results show a higher amount of the 2-CTX degradation product (Formula (IV)) at pH 2.0 and 4.0 as compared to the formulations of higher pH 6.0 (Figure 1A). The results show that the present of 2-hydroxypropyl-β-cyclodextrin in the formulation results in a low amount of 2-CTX of 0.004% at t=36h (Figure 2A). Table 5 displays the amount of 2-CTX in the different formulations of the example. Table 5: amount of 2-CTX in the formulations at t=0, and after 17 and 36 days. Unknown Total The amount of unknown degradation products was found to be higher at the lower pH 2.0 and 4.0 as compared to the higher pH 6.0, where no unknown degradation products were found, both in the absence or presence of a buffer (Figure 1D). The amount of unknown degradation products was found to be lowest in compositions comprising 2- hydroxypropyl-β-cyclodextrin (Figure 2D). Table 6 displays the amount of unknown degradation products in the different formulations of the example. Table 6: amount of unknown degradation products in the formulations at t=0, and after 17 and 36 days. Conclusion: The present example demonstrates that the stability of zuclopenthixol is lower in formulations having a low pH of 2.0 and 4.0, as is observed by the formation of higher amounts of degradation products for formulations 1, 2, 4, and 6. Formulations having a higher pH of 6.0 show less degradation products in general. The formulation of pH 6.0 was, however, found to develop a yellow colour over time. Addition of a buffer to the composition was found to provide a more stable pH over a 5 week period, however, the stable pH was found to have no positive impact on the stability of zuclopenthixol in the formulation. For certain formulations comprising a buffer, the stability of zuclopenthixol was found to be lower than for the formulation comprising no buffer. When comparing formulations at pH 4.0 comprising no buffer, AcOH buffer, 2-hydroxypropyl-β- cyclodextrin, or sulfobutylether-β-cyclodextrin Sodium, it is clear that the presence of 2- hydroxypropyl-β-cyclodextrin in the formulation provides a markedly higher stability of zuclopenthixol in the formulation, as demonstrated by the lower amounts of degradation products. The same effect was not found in formulations comprising sulfobutylether-β-cyclodextrin sodium, wherein especially a high content of dicarbinol was observed. In conclusion, the formulation comprising 2-hydroxypropyl-β-cyclodextrin was found to provide the best chemical stability of zuclopenthixol. Example 3: Influence of pH in formulations comprising cyclodextrins The aim of this examples was to study the impact of pH on the stability of Zuclopenthixol in a formulation comprising cyclodextrin, specifically comprising 2-hydroxypropyl-β-cyclodextrin or sulfobutylether-β cyclodextrin sodium. The example was performed in order to identify the optimal pH for a pharmaceutical formulation comprising zuclopenthixol and cyclodextrin, and to test whether different pH would result in complex formation between zuclopenthixol and different cyclodextrins. Materials and methods: The influence of different parameters on Zuclopenthixol stability and degradation was studied by preparation of different formulations 9-19, table 7: Table 7: Overview of formulations tested Preparation of samples: The test formulations were prepared in a batch size of 150 mL, as described below for each formulation. In general, a fresh bottle of ethanol was used in order to decrease the risk of peroxide content in ethanol thereby lowering the risk of oxidation due to peroxide content. After end preparation the formulations were gassed with sterile filtered argon for 2 minutes and sealed with a cap and parafilm to reduce risk of evaporation. All formulations were prepared with protection from light using amber colored flasks. For stochiometric 1:1 API:CD complex corresponds to approximately 8% (w/v) 2-hydroxypropyl-β- cyclodextrin content in the formulations. However, addition of 2-hydroxypropyl-β-cyclodextrin above the stoichiometric amount could be advantageous to ensure full protection. Based on this, 8% (w/v) 2-hydroxypropyl-β-cyclodextrin concentration was used in the formulations. Stock formulation A: To a 500 mL volumetric flask was added 23 g Zuclopenthixol 2HCl and 100 g 2-hydroxypropyl-β- cyclodextrin (Kleptose, degree of substitution of 0.62). ELGA water was added to the flask and the volume adjusted to 500 mL. Formulation 11: To a glass beaker was added 75 mL of stock formulation A and pH was adjusted to 3.0 by addition of 5 M NaOH. The solution was transferred to a 150 mL volumetric flask and the volume was adjusted to 150 mL with ELGA water. Formulation 12: To a glass beaker was added 75 mL of stock formulation A and pH was adjusted to 4.0 by addition of 5 M NaOH. The solution was transferred to a 150 mL volumetric flask and the volume was adjusted to 150 mL with ELGA water. Formulation 13: To a glass beaker was added 75 mL of stock formulation A and pH was adjusted to 5.0 by addition of 5 M NaOH. The solution was transferred to a 150 mL volumetric flask and the volume was adjusted to 150 mL with ELGA water. Formulation 14: To a glass beaker was added 75 mL of stock formulation A and pH was adjusted to 6.0 by addition of 5 M NaOH. The solution was transferred to a 150 mL volumetric flask and the volume was adjusted to 150 mL with ELGA water. Formulation 15: To a glass beaker was added 75 mL of stock formulation A and pH was adjusted to 7.0 by addition of 5 M NaOH. The solution was transferred to a 150 mL volumetric flask and the volume was adjusted to 150 mL with ELGA water. Formulation 16: Weigh out 2.9 g Zuclopenthixol 2HCl to a 100 ml volumetric flask. Add 70 mL ELGA water. Adjust pH to 2.0 with 5 M NaOH. Add 12.5 g Captisol. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 9 was prepared as described in example 2. Formulation 17: Weigh out 2.9 g Zuclopenthixol 2HCl to a 100 ml volumetric flask. Add 70 mL ELGA water. Adjust pH to 6.0 with 5 M NaOH. Add 12.5 g Captisol. The volume was adjusted to 100 mL with ELGA water before transfer of the solution to suitable utensil and addition of 25.0 mL Ethanol 96%. Formulation 10, 18 and 19: Due to low solubility of β-CD, formulations 10, 18 and 19 were discarded prior to the stability study. Stability study: 10 mL of each of the test formulations prepared according to the above method was transferred to Eltang glass tubes (glass type 1, clear glass) which were sealed and stored at 40 °C, 75%RH with protection from light throughout the experiment. Samples were withdrawn after 0, 2, 4, and 19 weeks and analyzed according to the methods below. Amount of degradation products: To measure the content of degradation products, the withdrawn samples were analyzed by HPLC, using a Symmetry Shield RP18, 50 x 2.1 mm ID, 3.5 μm column, mobile phases A: 0.04% TFA in water, B: 0.04% TFA in MeCN, C: methanol. The flow was 0.6 ml/min with a temperature of 40 °C. The injection volume was 10 µL and detection was UV at 270 nm. The gradient was linear with the points 0 min: 82% A, 18% B, 0% C to 8 min: 82% A, 18% B, 0% C to 17 min: 5% A, 10% B, 85% C to 19 min: 5% A, 10% B, 85% C to 30 min: 82% A, 18% B, 0% C. pH of the withdrawn samples was measured using a Metrohm 780 pH meter. Absorbance of the withdrawn sample was measured using an Agilent Cary 60 UV spectrophotometer. Results: Effect of pH on the stability of zuclopenthixol In general, a low level of degradation is observed for formulations comprising 2-hydroxypropyl-β- cyclodextrin and having a pH of 4 or higher (pH 4, 5, 6, and 7). The amount of degradation products arising from hydrolysis or oxidative degradation is lower at pH 5, 6, and 7 than at pH 3 or 4 (Figures 3 A-C). At pH 3 and 7 an unknown degradation product appears (Figure 3D). For the formulations comprising Sulfobutylether-β cyclodextrin Sodium, the stability of zuclopenthixol was found to be higher at higher pH. This may be seen by the highest content of degradation products in the formulation at pH 2.0, while the formulation at pH 6.0 showed the lowest content (Figures 4 A- D). Effect of cyclodextrins on stability of zuclopenthixol When comparing the stabilizing effect of the formulations comprising cyclodextrin at varying pH, it is clear that formulations comprising 2-Hydroxypropyl-β-cyclodextrin provides a significant higher stability of zuclopenthixol than does the formulations comprising Sulfobutylether-β cyclodextrin Sodium. This is e.g. seen by comparing the best Sulfobutylether-β cyclodextrin Sodium formulation at pH 6 at timepoint 36 days with the formulations comprising 2-hydroxypropyl-β-cyclodextrin at pH 5 and 6 at timepoint 19 weeks, wherein the level of degradation product is lower for the 2- hydroxypropyl-β-cyclodextrin formulation, despite the longer time of storage for the 2-hydroxypropyl- β-cyclodextrin formulation. Beta cyclodextrin The solubility of β-cyclodextrin was found to be low at all three pHs tested. The samples were therefore not analyzed in the stability study. Degradation products Carbinol The amount of carbinol degradation product (Formula (II)) was found to be low for all samples tested, with the only exception being the Kleptose pH 3.0 formulation which showed 0.021% carbinol after 19 weeks of storage (Figures 3B and 5B). Table 8 displays the amount of carbinol in the different formulations of the example. Table 8: amount of carbinol in the formulations at t=0, and after 4 and 19 weeks (kleptose) or 17 and 36 days (captisol). Dicarbinol The amount of dicarbinol degradation product (Formula (III)) was found to be lowest at higher pH, with the kleptose comprising formulations having a pH of 5, 6, and 7 showing the lowest amount (Figure 3C). For the captisol comprising formulations, the stability was also found to be highest at higher pH 6.0 (Figure 5C), however, even after only 36 d of storage, the dicarbinol content was higher than for the kleptose formulations at pH 5, 6, and 7, after 19 weeks of storage. Table 9 displays the amount of dicarbinol in the different formulations of the example. Table 9: amount of dicarbinol in the formulations at t=0, and after 4 and 19 weeks (kleptose) or 17 and 36 days (captisol). 2-CTX The amount of the 2-CTX degradation product (Formula (IV)) was found to be low in kleptose containing formulations, with the formulations as higher pH 5, 6, and 7 showing the lowest amount (Figure 3A). For the captisol comprising formulations, the stability was also found to be highest at higher pH 6.0 (Figure 5A), however, even after only 36 days of storage, the 2-CTX content was higher than for the kleptose formulations at pH 5, 6, and 7, after 19 weeks of storage. Table 10 displays the amount of 2-CTX in the different formulations of the example. Table 10: amount of 2-CTX in the formulations at t=0, and after 4 and 19 weeks (kleptose) or 17 and 36 days (captisol). Unknown Total The amount of unknown degradation products was low for formulations having a pH of 4, 5, and 6 (kleptose) and pH 6 (captisol) (Figures 3D and 5D). At pH 3 and 7 in the kleptose comprising formulations, an unknown degradation product appeared. Table 11 displays the amount of unknown degradation products in the different formulations of the example. Table 11: amount of unknown degradation products in the formulations at t=0, and after 4 and 19 weeks (kleptose) or 17 and 36 days (captisol). The colour, appearance and pH of the formulations Colour and appearance of the sample comprising kleptose was analyzed by visual appearance and by measuring absorbance at 410 nm and 440 nm. The samples were analyzed at timepoints 2 weeks, 4 weeks and 19 weeks. The formulation with pH 6 was found to be the most stable formulation, closely followed by the formulation with pH 5 and pH 7. All three formulations were clear and colourless at all timepoints measured (Figures 4 A and B). A larger change in colour and absorbance at 410 and 440 nm was observed when lowering pH of the formulation (pH 4 and pH 3). pH of the formulations The pH of all kleptose comprising formulations appeared stable over time, despite the absence of a buffering agent. See further in below table 12. Table 12: pH of the formulations at timepoints 0, 2 weeks, 4 weeks, and 19 weeks. Comparative stability The stability of Zuclopenthixol in the best performing formulations 13 and 14 was compared to a formulation comprising 20 mg/mL zuclopenthixol at pH 2 comprising no cyclodextrin and wherein no adjustment of the pH is performed. The 19 weeks timepoint data of formulations 13 and 14 was compared to data of the pH 2.0 no CD formulation after 12 weeks storage at 40 °C and 75%RH. The level of degradation was found to be significantly lower for the optimized formulations 13 and 14 (Figure 6), when compared to the pH 2.0 no Cd formulation. Hence a very good effect on the stability of zuclopenthixol was observed by the presence of 2-hydroxypropyl-β-cyclodextrin and at a higher pH of 5 or 6. Conclusion: The study shows a markedly improved stability of zuclopenthixol with formulations comprising 2- hydroxypropyl-β-cyclodextrin and having a pH in the range of 4-7 all displayed an increased stability of zuclopenthixol. The best stability was found for the formulation comprising 2-hydroxypropyl-β- cyclodextrin having a pH of 6, closely followed by the formulation comprising 2-hydroxypropyl-β- cyclodextrin having a pH of 5. The results suggest that an inclusion complex is formed between zuclopenthixol and 2-hydroxypropyl- β-cyclodextrin in the formulations, whereby the double bond in zuclopenthixol is protected in the API:CD complex, increasing the stability of zuclopenthixol in the aqueous formulation and reducing the degradation of zuclopenthixol by hydrolysis and/or oxidative degradation. The data further suggest that the strongest inclusion complex between zuclopenthixol and 2-hydroxypropyl-β- cyclodextrin is formed at pH 5-6, thereby providing the best protection and highest stability. Example 4: Stress stability study of zuclopenthixol composition comprising 2-hydroxypropyl-β- cyclodextrin The aim of the present example was to test the stability and pharmaceutical applicability of the composition of the present invention, by analyzing the composition on various parameters, including degradation, drop rate, drop measure, uniformity of dose, and absorbance. Materials and methods Experimental design: The pharmaceutical composition tested comprises Zuclopenthixol 20 mg/mL, 10% 2-hydroxypropyl-β- cyclodextrin, 12% ethanol (w/v, 96%), pH adjusted to 5.0 with 1 M NaOH. The composition was prepared according to the method as described in example 1. To a 25 mL drop bottle of glass type III was added 22 mL of the pharmaceutical composition and the bottle was fitted with a drop aggregate and closed with a cap. Stability study: The sample was placed in stress stability at 40°C/75% RH. Samples were withdrawn and analyzed after 1, 2, 3, and 6 months. Amount of degradation products: To measure the content of degradation products, the withdrawn samples were analyzed by HPLC, using a X-Bridge phenyl, 75 mm x 4.6 mm (ID) x 2.5µm column, mobile phase Acetate buffer 25mM pH 5.2/Acetonitrile (70/30), using isocratic elution. The flow was 1.1 ml/min with a temperature of 40 °C. The injection volume was 30 µL and detection was UV at 270 nm. pH of the withdrawn samples was measured using a Metrohm 780 pH meter. Absorbance of the withdrawn sample was measured using an Agilent Cary 60 UV spectrophotometer. Colour and clarity was evaluated by visual inspection of the samples as described in Ph.Eur. (European pharmacopeia, 10 ^th edition). Dropping speed was measured by placing a flask in a vertical position and count the number of drops delivered in 10 seconds. The test was repeated three times and an average was calculated. Uniformity of Dose was determined as described in Ph.Eur. (European pharmacopeia, 10 ^th edition) (liquid preparations for oral use). Results The optimized pharmaceutical formulation was analyzed on various parameters as listed in below tables 15-17. Stability and pharmaceutical applicability of formulation The formulation was found to provide a stable pharmaceutical formulation having a stable density and pH of the formulation of the period of the 6 months storage time (Table 13). Also, the drop measure and drop rate was found to be stable over the time course of the experiment. Furthermore, it was found that the API content of zuclopenthixol was stable of the time course of the experiment, resulting in a good uniformity of dose. The observed stability of the formulation in these parameters is important for the applicability of the formulation as a pharmaceutical formulation, specifically for the applicability of the formulation as an oral drop formulation. Table 13: Stability and pharmaceutical applicability of formulation as measured over the time course of 6 months Color and appearance of the formulation The formulation was found to have a high stability in color and appearance with the color being equal to or below GY7 and the solution being clear during the time course of the experiment (Table 14). Also, the absorbance of the solution as measured at 410, 440, and 600 nm was low during the time course of the experiment. Table 14: Color and appearance of the formulation as observed over the time course of 6 months Degradation products As seen by the data presented in below table 15, the amount of degradation products was generally very low, with the content of carbinol at 6 months being 0.00985%, dicarbinol 0.015724%, 2-CTX 0.02525, trans-clopenthixol 0.0606%, and total unkowns 0.04646%. All amounts are well below the specification for the zuclopenthixol oral drop formulation, as described above. Table 15: Amount of degradation products in the formulations at t=0, and after 1, 2, 3, and 6 months. Conclusion The results of this example demonstrate that the optimized formulation of zuclopenthixol comprising 2-hydroxypropyl-β-cyclodextrin at pH 5.0 provides a very high stability of zuclopenthixol, displaying good values on all parameters which are well within the specification for a pharmaceutically applicable formulation. Example 5: Characterization of zuclopenthixol:cyclodextrin complex The aim of this example was to estimate the equilibrium constant for a 1:1 Zuclopenthixol:2-HP-β-CD complex. Materials and methods: Samples 4A-J with increasing concentrations of 2-hydroxypropyl-β-cyclodextrin were prepared according to the below methods. The H-NMR spectra of each sample was recorded, and the equilibrium constant calculated according to the below methods. Stock solution A: Weigh out 11.85 g zuclopenthixol 2HCl to a 250 mL volumetric flask. Dissolve in ELGA water and adjust volume to 250 mL by addition of ELGA water. Stock solution B: Weigh out 50 g 2-hydroxypropyl-β-cyclodextrin (Kleptose, degree of substitution of 0.62) to a 250 mL volumetric flask. Dissolve in ELGA water and adjust volume to 250 mL by addition of ELGA water. Stock solution C: Measure out 100 mg trimethylsilylpropanesulfonic acid sodium salt (DSS) to a 5 mL volumetric flask. Dissolve in D2O and adjust volume to 5 mL by addition of D2O. Stock solution D: Measure 25.0 mL stock solution A to a suitable utensil. Adjust pH to 4.0 by addition of 5 M NaOH and transfer the solution to a 50 mL volumetric flask using several volumes of ELGA water and adjust volume to 50 mL by addition of ELGA water. Samples 4A-J: To 10 suitable containers (A-J) was added: 1.0 mL stock D + 200 µL stock C To the respective samples was then added: Sample 4A: 0 mL stock B + 3.8 mL ELGA water Sample 4B: 0.1 mL stock B + 3.7 mL ELGA water Sample 4C: 0.2 mL stock B + 3.6 mL ELGA water Sample 4D: 0.3 mL stock B + 3.5 mL ELGA water Sample 4E: 0.4 mL stock B + 3.4 mL ELGA water Sample 4F: 0.5 mL stock B + 3.3 mL ELGA water Sample 4G: 0.6 mL stock B + 3.2 mL ELGA water Sample 4H: 0.8 mL stock B + 3.0 mL ELGA water Sample 4I: 1.2 mL stock B + 2.6 mL ELGA water Sample 4J: 3.8 mL stock B + 0 mL ELGA water DSS was found to be unsuitable as a chemical shift reference, and therefore acetone was added subsequently to each sample as an alternative chemical shift reference. The concentration of 2-hydroxypropyl-β-cyclodextrin in each sample 4A-J is listed in table 16A below. Table 16A: Concentration of 2-HP-β-CD in samples 4A-J. Sample [2-HP-β-CD] (M) 4A 0 4B 0.0036 4C 0.0072 4D 0.0108 4E 0.0144 4F 0.0180 4G 0.0216 4H 0.0288 4I 0.0432 4J 0.1368 NMR spectra were recorded for each sample on a Bruker 600-Avance-III spectrometer equipped with a 5 mm TCI cryoprobe operating at 600.16 MHz for ¹ H. The δ _rel.acetone , which is the chemical shift of vinyl proton of zuclopenthixol when the NMR-spectrum is calibrated to that of the acetone chemical shift reference, was determined for each sample 4A-J. Data were fitted relative to molar concentrations using an expression of the form: ^^^ ^ + ^ ⁽ ^^ ⁾ + 1 ^^ ^^ − ^{^} ^0.0025 + ^ ⁽ ^^ ⁾ + 1 ^^ ^^^^^ ^ ^ 0.0025 2 Wherein ddmax was the theoretical maximum of the Δδ value, c(CD) was the concentration of 2- hydroxypropyl-β-cyclodextrin of the respective sample, and K was the equilibrium constant for the formation of a 1:1 API:CD complex. Results: The recorded δrel.acetone for each sample is listed in below table 16B. The Δδ relative to sample 4A was calculated for each of samples 4B-J. Table 16B: Chemical shift as measured in the different samples 4A-J, as well as Δδ relative to sample A. Sample δrel.acetone Δδ 4A 5.906 0.000 4B 5.997 0.091 4C 6.073 0.167 4D 6.084 0.178 4E 6.089 0.183 4F 6.091 0.185 4G 6.091 0.185 4H 6.089 0.183 4I 6.086 0.180 4J 6.083 0.177 Fitting the data using the above equation and using JMP found a value for ddmax of 0.194±0.008 and an equilibrium constant K of 700±244 M ^-1 . Error estimates are standard error. Conclusion: The present experiment demonstrates that a 1:1 complex between zuclopenthixol and 2- hydroxypropyl-β-cyclodextrin is formed having an equilibrium constant of about 700 M ^-1 at pH 4, indicating formation of a strong complex. Such complex formation may result in protection of zuclopenthixol from degradation, thus resulting in an increased stability of zuclopenthixol in an aqueous solution. Without being bound by theory, at higher pH, such as pH of 5 or 6, the equilibrium constant is expected to be higher than the K determined in the present example at pH 4, due to zuclopenthixol being less positively charged at higher pH, thereby increasing the hydrophobicity, and increasing the binding of the molecule within the more hydrophobic interior of the cyclodextrin. Example 6: Microbiological tests of sample The aim of this study was to test whether the pharmaceutical composition of the present disclosure was pharmaceutically applicable, specifically related to microbial growth in the sample. Materials and methods The pharmaceutical composition was prepared according to the method described in example 1. In a first sample, the composition was stored in brown type III glass bottles with a drop aggregate inserted and closed with a screw cap. The sealing was broken and samples were withdrawn at t=0, and after 6 weeks of storage at 25°C/60% RH in the dark and analyzed to identify any potential microbial growth after breakage of the seal (microbiological quality) according to the below method. Microbiological Quality The test for microbiological quality (Microbial enumeration test and Escherichia Coli test) was carried out according to Ph.Eur.2.6.12 (USP <61>) and Ph.Eur 2.6.13 (USP <62>). In a second sample, the preservative effect of the formulation when challenged with different microorganisms (antimicrobial capacity test) was performed with reference to Ph.Eur.5.1.3. The study was designed to confirm the efficacy of antimicrobial preservation of the formulation. The test organisms used were: Candida albicans, Aspergillus brasiliensis, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. Start levels of organisms in the challenge were (Table 17): Table 17: Start level of Candida albicans, Aspergillus brasiliensis, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. Samples were withdrawn at t=0, and after 14 and 28 days after challenge with the respective organisms and analyzed for microbial growth. Results The microbiological quality of the first sample is listed in below table 18. Table 18: Microbiological quality TAMC: total aerobic microbial count; TYMC: total combined yeasts/moulds count The microbial growth in the second sample is listed in below table 19. Table 19: Microbial growth Conclusion This example demonstrates that the pharmaceutical composition of the present disclosure, comprising ethanol, satisfies the requirements of pharmaceutical applications with respect to microbiological quality and antimicrobial preservation. Example 7: Stability study of zuclopenthixol composition comprising 2-hydroxypropyl-β- cyclodextrin The aim of the present example was to test the stability and pharmaceutical applicability of the composition of the present invention during storage at 25°C/60% RH, by analyzing the composition on various parameters, including degradation, appearance and API content. Materials and methods The pharmaceutical composition tested comprised Zuclopenthixol 20 mg/mL, 10% 2-hydroxypropyl- β-cyclodextrin, 12% ethanol (w/v, 96%), pH adjusted to 5.0 with 5 M NaOH. The composition was prepared according to the method as described in example 1. To a 25 mL drop bottle of glass type III was added 22 mL of the pharmaceutical composition and the bottle was fitted with a drop aggregate and closed with a cap. Stability study: The sample was placed in stability at 25°C/60% RH. Samples were withdrawn and analyzed after 3, 6, 9, 12 and 18 months. Amount of degradation products: To measure the content of degradation products, the withdrawn samples were analyzed by HPLC, using a X-Bridge phenyl, 75 mm x 4.6 mm (ID) x 2.5µm column, mobile phase Acetate buffer 25mM pH 5.2/Acetonitrile (70/30), using isocratic elution. The flow was 1.1 ml/min with a temperature of 40 °C. The injection volume was 30 µL and detection was UV at 270 nm. pH of the withdrawn samples was measured using a Metrohm 780 pH meter. Colour and clarity was evaluated by visual inspection of the samples as described in Ph.Eur (European pharmacopeia, 10 ^th edition). Results The optimized pharmaceutical formulation was analyzed on various parameters as listed in below tables 20-21. Stability and pharmaceutical applicability of formulation The formulation was found to provide a stable pharmaceutical formulation having a stable pH of the formulation of the period of the 18 months storage time (Table 20). Furthermore, it was found that the API content of zuclopenthixol was stable over the time course of the experiment. The formulation was found to have a high stability in color and appearance with the color being equal to or below GY7 and the solution being clear during the time course of the experiment (Table 20). Table 20: Color and appearance, API content and pH of formulation as measured over the time course of 18 months Degradation products As seen by the data presented in below table 21, the amount of degradation products was generally very low, with the contents of carbinol, at 18 months being <0.05 %w/w, dicarbinol <0.05 %w/w, 2- CTX <0.05 %w/w, trans-clopenthixol 0.10 %w/w, and total unknowns <0.05 %w/w. All amounts are well below the specification for the zuclopenthixol oral drop formulation, as described above. Table 21: Amount of degradation products in the formulations at t=0, and after 3, 6, 9, 12, and 18 months. Conclusion The results of this example demonstrate that the optimized formulation of zuclopenthixol comprising 2-hydroxypropyl-β-cyclodextrin at pH 5.0 provides a very high stability of zuclopenthixol, displaying good values on all parameters which are well within the specification for a pharmaceutically applicable formulation. Example 8: Stability study of Flupentixol composition comprising 2-hydroxypropyl-β-cyclodextrin The aim of this examples was to investigate the ability of 2-hydroxypropyl-β-cyclodextrin to stabilize Flupentixol in a formulation and to prevent degradation of Flupentixol in the formulation, such as prevent degradation by hydrolysis and/or oxidative degradation as described in this example. Materials and methods: The chemical structure of Flupentixol is disclosed below according to formula (VI). Flupentixol is found as a mixture of the Z and the E isomer. The influence of different parameters on Flupentixol stability and degradation was studied by preparation of different formulations 20-23, table 22: Formulation 20 was prepared with same pH, ethanol content and stoichiometric ratio between active ingredient and 2-hydroxypropyl-β-cyclodextrin as for the optimized zuclopenthixol formulations of the previous examples 4 and 7. In addition, formulations 21 and 22 were tested with varying of the ethanol content, and the pH was varied in formulation 23 to natural pH=2. Table 22: Overview of formulations tested Preparation of samples: The test formulations were prepared as described below for each formulation. All formulations were prepared with protection from light. Formulation 20: To a 500 ml volumetric flask was added 100 g of 2-hydroxypropyl-β-cyclodextrin and 150 mL Purified water. Upon stirring was added 60 g of ethanol 96% and subsequently 23.36 g of Flupentixol 2HCl. When all solids were dissolved, pH was adjusted to 5.0 by addition of 5 M NaOH. The volume was adjusted to 500 mL with ELGA water before transfer of the solution to suitable utensil for stability, as described below. Formulation 21: To a 500 ml volumetric flask was added 100 g of 2-hydroxypropyl-β-cyclodextrin and 150 mL Purified water. Upon stirring was added 100 g of ethanol 96% and subsequently 23.36 g of Flupentixol 2HCl. When all solids were dissolved, pH was adjusted to 5.0 by addition of 5 M NaOH. The volume was adjusted to 500 mL with ELGA water before transfer of the solution to suitable utensil for stability, as described below. Formulation 22: To a 500 ml volumetric flask was added 100 g of 2-hydroxypropyl-β-cyclodextrin and 150 mL Purified water. Upon stirring was added 150 g of ethanol 96% and subsequently 23.36 g of Flupentixol 2HCl. When all solids were dissolved, pH was adjusted to 5.0 by addition of 5 M NaOH. The volume was adjusted to 500 mL with ELGA water before transfer of the solution to suitable utensil for stability, as described below. Formulation 23: To a 500 ml volumetric flask was added 100 g of 2-hydroxypropyl-β-cyclodextrin and 150 mL Purified water. Upon stirring was added 60 g of ethanol 96% and subsequently 23.36 g of Flupentixol 2HCl. When all solids were dissolved, the volume was adjusted to 500 mL with ELGA water before transfer of the solution to suitable utensil for stability, as described below. Stability study: 10 mL of each of the test formulations prepared according to the above method was transferred to type III glass bottles which were sealed and stored at 40 °C, 75%RH for 1-3 months with protection from light throughout the experiment. Samples were withdrawn after 0, 1, and 3 months and analyzed according to the below methods. Formulations 21 and 22 were discarded after 1 month due to low stability observed, as further described below. pH of the withdrawn samples was measured using a Metrohm 780 pH meter. Amount of degradation products: To measure the content of degradation products, the withdrawn samples were analyzed by HPLC, using a X-Bridge phenyl 75 x 4.6 mm (ID), 2.5 µm column, mobile phase: A: Ammonium Acetate buffer pH 6.5 with 0.5 % TEA, B: Acetonitrile (gradient A/B: 65/35). The flow was 1.1 mL/min with a temperature of 40 °C and runtime of 30 min. The injection volume was 30 µL and detection was UV at 270 nm. Results: Upon degradation of Flupentixol, the following degradation products are observed: Formula (VII), also referred to herein as Sulfoxide-F. , Formula (XI), also referred to herein as Thioxanthone-F. pH and Flupentixol content: The pH and Flupentixol content of the formulations were measured during the time course of the experiment. pH was found to be stable, whereas a small decrease in Flupentixol content was observed over time for all formulations (table 23). Table 23: pH and Flupentixol content of formulation at t=0 – 3 months of stability test Colour, clarity and absorbance (410nm and 440 nm): Stability of the formulations in terms of colour, clarity, and absorbance (410nm and 440 nm) was analyzed during the time course of the experiment (Tables 24 and 25). A worsening of the colour from ≤ GY7 to ≤ GY4-5 was observed for all four formulations already after 1 month. After 3 months the colour of formulations 20 and 23 were further worsened. Formulation 20 was found to already at t=0 be less clear than water (clear I) and turned into a suspension after 3 months (susp II). Increasing the amount of ethanol (formulations 21-22) or lowering of pH (formulation 23) provided an improvement and these formulations were found to be clear during the time course of the experiment. The absorbance was found to increase dramatically for formulation 20 at both 410 nm and 440 nm. Increasing the amount of ethanol or lowering of pH resulted in even higher increases in absorbance (formulations 21-23). Table 24: Color and clarity of formulation at t=0 – 3 months of stability test Table 25: Absorbance of formulation at t=0 – 3 months of stability test Amount of degradation products: Flupentixol in formulation 20 was found to degrade to Sulfoxide-F, Dicarbinol-F, Carbinol-ethanol-F, and Thioxanthone-F degradation products in high amounts already after 3 months. In contrast, no Carbinol-F or unknown degradation products were observed (table 26-27). Increasing the amount of ethanol (formulations 21-22) was found to result in even higher amounts of the Sulfoxide-F, Dicarbinol-F, Carbinol-ethanol-F, and Thioxanthone-F degradation products. Lowering of the pH (formulation 23) was also found to result in higher amounts of the degradation products as compared to formulation 20. Conclusion: The present example demonstrates that 2-HP-β-CD was not capable of stabilizing Flupentixol in a formulation. The low stability was demonstrated on all tested parameters; colour, clarity, absorbance, and amount of degradation products. Adjustment of ethanol content or pH did not improve stability. The example demonstrates that despite the high similarity in chemical structure between zuclopenthixol and flupentixol, a stabilizing effect of cyclodextrin cannot be predicted and the stabilizing effect of 2-HP-β-CD on zuclopenthixol was not directly translatable to the structurally similar Flupentixol.

Table 26: Amount of degradation products of Flupentixol in formulations at t=0 – 3 months of stability test 27: Amount of degradation products of Flupentixol in formulations at t=0–3 months of test Fo r 2 2 2 _m 3 2 1 20 u l _a t _i 0 . ₁ 07 0 . ₂ 06 0 . ₂ 41 0 . ₀ 41 0 . ₁ 60 _o t _a l _U 0 1 . _{2 m} n 4 0 0 0 k o n 4 n o t _h w ns ( 3 _% 0 . _m w 3 o / 3 - - ⁰ w 0 n t _h ) s