Patent Publication Number: US-2019183896-A1

Title: One step milling process for preparing micronized paliperidone esters

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of U.S. Provisional Application Ser. No. 62/598,827, filed Dec. 14, 2017, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to a process for preparing micronized paliperidone esters. 
     BACKGROUND OF THE INVENTION 
     Paliperidone palmitate is an atypical antipsychotic agent belonging to the chemical class of benzisoxazole derivatives. The chemical name for paliperidone palmitate is 3-(2-(4-(6-fluoro-3a,7a-dihydrobenzo[d]isoxazol-3-yl)piperidin-1-yl)ethyl)-2-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-9-yl palmitate and is represented by the following formula: 
     
       
         
         
             
             
         
       
     
     Currently, paliperidone palmitate is approved by the US Food and Drug Administration and the European Medicines Agency for the treatment of schizophrenia or a schizoaffective disorder. Additionally, paliperidone palmitate can be used to treat mania and at lower doses as maintenance for bipolar disorders. 
     Paliperidone palmitate can be formulated for parenteral administration. It was previously discovered that the particle size distribution of paliperidone palmitate determines the extended release kinetics of the formulations. Currently, paliperidone palmitate is micronized using air-jet mills or a multi-step wet milling process. Generally, sterile air-jet milling is carried out in isolators or by using a restricted access barrier system. 
     Paliperidone palmitate has been previously formulated for an extended-release suspension for intramuscular injection. The extended-release formulation is the result of the suspension having a range of paliperidone palmitate particle sizes. The range of paliperidone palmitate particle sizes is due to a multi-step wet milling process. The multi-step wet milling process requires the use of at least two different sized milling media, wherein a filtration or separation step is required to remove the first milling media before addition of the second milling media. 
     Thus, there is a need to develop a manufacturing process that is more controlled than prior methods. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a process for preparing a micronized paliperidone ester. The process comprises wet milling a suspension comprising a solid paliperidone ester, at least one suspending agent, and at least one wetting agent in the presence of a plurality of polymeric beads to form the micronized paliperidone ester, wherein the plurality of polymeric beads has an average diameter from about 0.5 mm to about 1.5 mm, and the micronized paliperidone ester has a particle size distribution from about 1 μm to about 30 μm. 
     Other aspects and iterations of the disclosure are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
         FIG. 1  depicts particle size distribution of polystyrene milled paliperidone palmitate particles at different milling time points. 
         FIG. 2  depicts dissolution profile of polystyrene milled paliperidone palmitate particles at different milling time points using a USP type 2 apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure provides injectable pharmaceutical compositions that provide controlled release of an active pharmaceutical ingredient. Also provided are methods of making the controlled release pharmaceutical composition. The methods comprise a one-step wet milling process to provide a particle size distribution of the active pharmaceutical ingredient to obtain a controlled release formulation. The pharmaceutical compositions disclosed herein comprise at least one wetting agent, at least one suspending agent, and at least one active pharmaceutical ingredient. The pharmaceutical composition may further comprise at least one buffer and at least one pH modifier. Applicants of the present invention discovered that the milling of the active pharmaceutical ingredient with the other components, specifically, a wetting agent and a suspending agent, provides better control of the milling process which in turn provides better control of particle size distribution of the active pharmaceutical ingredient and prevents the generation of fine particles. The pharmaceutical compositions disclosed herein are milled in a one step process using polymeric beads. The resulting pharmaceutical composition provides better control of the controlled release profile. 
     (I) Process for Preparing Micronized Paliperidone Ester 
     One aspect of the disclosure encompasses a process for preparing micronized paliperidone ester. The process comprises wet milling a suspension comprising solid paliperidone ester, at least one suspending agent, and at least one wetting agent in the presence of polymeric beads to form the micronized paliperidone ester, wherein the polymeric beads have an average diameter from about 0.5 mm to about 1.5 mm and the micronized paliperidone ester has a particle size distribution from about 1 μm to about 30 μm. 
     (a) Forming the Suspension 
     The first step of the process comprises forming a suspension comprising a solid paliperidone ester, at least one suspending agent, and at least one wetting agent. The process for forming the suspension generally takes place under aseptic conditions. Such methods are generally known in the art.
         (i) Active Pharmaceutical Ingredient (API)       

     The suspension comprises at least one API or salt thereof. Suitable APIs include, without limit, atypical antipsychotics (e.g., amisulpride, aripiprazole, asenapine, blonanserin, clozapine, Iloperidone, lurasidone, melperone, olanzapine, paliperidone, paliperidone esters (e.g., paliperidone palmitate), perospirone, quetiapine, remoxipride, risperidone, sertindole, sulpiride, and ziprasidone). In specific embodiments, the API is a paliperidone ester. In further embodiments, the paliperidone ester is paliperidone palmitate. 
     Any of the above-mentioned APIs may be incorporated in the suspension described herein in any suitable form, such as, for example, as a pharmaceutically acceptable salt, uncharged or charged molecule, molecular complex, solvate or hydrate, prodrug, and, if relevant, isomer, enantiomer, racemic mixture, and/or mixtures thereof. Furthermore, the API may be in any of its crystalline, semi-crystalline, amorphous, or polymorphous forms. In an exemplary embodiment, the API may be in a crystalline form. 
     The crystalline, semi-crystalline, amorphous, or polymorphous forms may have a particle size of about 10 to about 200 μm. In some embodiments, the crystalline, semi-crystalline, amorphous, or polymorphous forms may have a particle size of about 10 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, about 190 μm, or about 200 μm. 
     The amount of API in the suspension can and will vary depending upon the active agent. In certain embodiments, the API in the suspension is paliperidone palmitate. In certain embodiments, the amount of paliperidone palmitate before milling may range from about 3% to about 60% w/v, from about 4% to about 50% w/v, from about 5% to about 40% w/v, from about 6% to about 35% w/v, from about 7% to about 30% w/v, from about 8% to about 25% w/v, or from about 10% to about 15% w/v of the suspension. In certain embodiments, the amount of paliperidone palmitate in the suspension may be about 5%, about 8%, about 10%, about 12%, about 14%, about 16%, about 18%, about 20%, about 25%, about 30%, or about 35% w/v of the suspension. 
     (ii) Suspending Agent 
     The suspension comprises at least one suspending agent. In general, the at least one suspending agent provides long-term stabilization, facilitate drug adsorption, alter viscosity, or enhance solubility. 
     Suitable suspending agents include, without limit, polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol, and copolymers thereof); polyethylene glycols (e.g., PEG 300, PEG 400, PEG 600, PEG 1000, PEG 1100, PEG 1900, PEG 2000, PEG 2800, PEG 2900, PEG 3350, PEG 4000, PEG 6000, PEG 8000, PEG 8400, PEG 10,000, PEG 12,000, PEG 14600, PEG 17,000, etc.); and triblock polymer of polypropylene glycol flanked by polyethylene glycol (e.g., poloxamer 124, poloxamer 188, poloxamer 237, poloxamer 338, poloxamer 407, poloxamer 407, etc.). In an exemplary embodiment, the suspending agent may be polyethylene glycol 4000 (PEG 4000). 
     The amount of the at least one suspending agent present in the suspension can and will vary depending upon the identity of the suspending agent as well as the identity and/or amount of the other components in the suspension. In general, the amount of the at least one suspending agent in the suspension may range from about 2% to about 30% w/v, from about 3% to about 27% w/v, from about 4% to about 23% w/v, from about 5% to about 20% w/v, from about 7% to about 17% w/v, or from about 10% to about 14% w/v of the suspension. In some embodiments, the amount of the at least one suspending agent in the suspension may be about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, or about 20% w/v of the suspension. 
     (iii) Wetting Agent 
     The suspension also comprises at least one wetting agent. The at least one wetting agent can comprise amphiphilic compounds that contain polar, hydrophilic moieties as well as non-polar hydrophobic moieties. The wetting agent can be an anionic, cationic, a zwitterionic, or a non-ionic wetting agent. 
     Suitable wetting agents include, without limit, polyethylene glycol fatty acid monoesters (e.g., polyethylene glycol laurate or stearate, etc.); polyethylene glycol fatty acid diesters (e.g., polyethylene glycol dilaurate, disterate, dipalmitate, or dioleate, etc.); polyethylene glycol glycerol fatty acid esters (e.g., polyethylene glycol glycerol laurate, glycerol stearate, glycerol oleate, etc.); polyglycerized fatty acids (e.g., polyglyceryl laurate, oleate, or stearate; polyglyceryl mono and dioleate; etc.); sterol derivatives (e.g., polyethylene glycol cholesterol ether, polyethylene glycol cholestanol, polyethylene glycol phyto sterol, etc.); and polyethylene glycol sorbitan fatty acid esters (e.g., polysorbate 20, polysorbate 80, PEG-10 sorbitan laurate, PEG-20 sorbitan monolaurate, sorbitan tristearate, etc.). In an exemplary embodiment, the wetting agent may be polysorbate 20. 
     The amount of the at least one wetting agent present in the suspension can and will vary depending upon the identity of the wetting agent as well as the identity and/or amount of the other components utilized in the suspension. In general, the amount of the at least one wetting agent in the suspension may range from about 0.1% to about 10% w/v, from about 0.3% to about 8% w/v, from about 0.7% to about 5% w/v, or from about 1% to about 3% w/v of the suspension. In some embodiments, the amount of the at least one wetting agent in the suspension may be about 0.5%, about 1.0%, about 1.5%, about 2%, about 2.5%, about 3.0%, about 3.5%, about 4.0%, about 4.5%, or about 5% w/v of the suspension. 
     (b) Additional Components 
     (i) Buffer 
     The suspension may comprise at least one buffer. The identity of the buffer can and will vary depending on the pH of the suspension. Non-limiting examples of the buffer include the sodium or potassium salt of phthalate, phosphate, borate, and acetate. In an exemplary embodiment, the buffer may comprise sodium dihydrogen phosphate and/or disodium hydrogen phosphate. 
     In general, the amount of the at least one buffer in the suspension may range from about 0.1% to about 10% w/v, from about 0.2% to about 8% w/v, from about 0.3% to about 6% w/v, from about 0.4% to about 5% w/v, or from about 0.5% to about 3% w/v of the suspension. In certain embodiments, the amount of buffer in the suspension may be about 0.5%, about 1.0%, about 1.5%, about 2.0%, about 2.5%, or about 3.0% w/v of the suspension. 
     (ii) pH Modifier 
     The suspension may comprise at least one pH modifier to adjust the pH of the suspension. Non-limiting examples of a pH modifier include organic or inorganic acids and bases, for example, acetic acid, citric acid, benzoic acid, formic acid, fumaric acid, hydrochloric acid, lactic acid, malic acid, phosphoric acid, sorbic acid, sulfuric acid, tartaric acid, potassium carbonate, sodium carbonate, sodium bicarbonate, and sodium hydroxide. In certain embodiment, the pH modifier may comprise sodium hydroxide and citric acid. In a specific embodiment the pH modifier may be citric acid. 
     In general, the amount of the at least one pH modifier in the suspension may range from about 0.1% to about 10% w/v, from about 0.2% to about 8% w/v, from about 0.3% to about 6% w/v, from about 0.4% to about 5% w/v, or from about 0.5% to about 3% w/v of the suspension. In certain embodiments, the amount of pH modifier in the suspension may be about 0.5%, about 1.0%, about 1.5%, about 2.0%, about 2.5%, or about 3.0% w/v of the suspension. 
     The pH of the suspension may range from about 6 to about 9, from about 7 to about 8, or from about 7 to about 7.5. In certain embodiment, the pH of the suspension may be about 7.0, about 7.1, about 7.2, about 7.3, about 7.4, or about 7.5. 
     In an embodiment, forming the suspension is carried in a batch or continuous process. In an exemplary embodiment, forming the suspension is carried out in a continuous process. 
     (c) Wet Milling 
     The process further comprises milling the suspension to form micronized paliperidone ester. The process comprises milling the suspension to reduce particle size and generate a size distribution of micronized paliperidone ester particles. The milling process can be accomplished by techniques generally known in the art. Further, the milling process generally takes place under aseptic conditions. 
     The milling process generally utilizes milling media. The milling media may comprise polymeric beads. Non-limiting examples of polymeric beads include polystyrene, polyamide, polycarbonate, acrylic, crosslinked polystyrene, crosslinked polyamide, or crosslinked polycarbonate. In an exemplary embodiment, the milling media is polystyrene beads crosslinked with divinylbenzene. 
     The size of the polymeric beads may vary depending upon the desired particle distribution. In some embodiments, the size of the polymeric beads may range from about 0.2 mm to about 2.0 mm. In various embodiments, the size of the polymeric beads may range from about 0.5 mm to about 1.5 mm, from about 0.5 mm to about 1.0 mm, or from about 0.6 to about 0.8 mm. 
     The milling process reduces the size of the paliperidone ester to the desired particle size distribution. The milling process is preferably accomplished so that the particle size distribution provides satisfactory dosage content uniformity, dissolution profiles, and a controlled release profile. The particle size distribution may range from be from about 1 μm to about 30 μm or from about 2 μm to about 20 μm. In some embodiments, the dl 0 is from about 2 μm to about 3 μm, d50 is from about 6 μm to about 8 μm, and d90 is from about 15 μm to about 20 μm. 
     The time of the milling step can and will vary depending upon the components of the suspension. Additionally, the milling time may vary depending on the total amount of suspension prepared in Section (I)(a). In general, the milling step may proceed for about 1 minute to about 120 minutes, from about 5 minutes to about 60 minutes, from about 10 minutes to about 30 minutes. 
     The temperature of the milling step may also vary depending upon the identity of the API. In general, the milling step may occur at a temperature ranging from about 5° C. to about 40° C. In specific embodiments, the milling step may occur at room temperature or about 20-25° C. 
     The tip speed of the milling step can and will vary depending upon the mill utilized, media milling size, and final particle size distribution. In general, the milling speed may occur at from about 2 m/s to about 8 m/s. In further embodiments, the milling speed may occur at from about 3 m/s to about 6 m/s. 
     Following the milling process, the milling media is removed by standard techniques known in the art, and the micronized paliperidone ester suspension is diluted to the desired API concentration. 
     In an embodiment, the milling process is carried in a batch or continuous process. In an exemplary embodiment, the milling process is carried out in a continuous process. 
     (d) Scale 
     The process of preparing a micronized palmitate ester can be conducted at a bench top (e.g., 1 g to 100 g) to commercial scale (e.g., 0.5 to 1000 kg). 
     (II) Micronized Palmitate Ester 
     One aspect of the present disclosure provides a pharmaceutical composition that can be formulated to provide a controlled release of a micronized palmitate ester. Detailed below are the components and dosage forms of the pharmaceutical composition.
         (a) Components of the Pharmaceutical Composition       

     The pharmaceutical composition disclosed herein comprises at least one wetting agent, at least one suspending agent, at least one buffer, at least one pH modifier, and at least one active pharmaceutical ingredient. The order of component addition and the one-step milling process provide the desired API particle distribution which creates a controlled release formulation. 
     In an exemplary embodiment, the pharmaceutical composition comprises paliperidone palmitate, polysorbate 20, polyethylene glycol 4000, citric acid monohydrate, sodium dihydrogen phosphate, sodium hydroxide, and water for injection. In further exemplary embodiment, the pharmaceutical composition comprises paliperidone palmitate in an amount from about 25% to about 40% by weight of the composition, polyethylene glycol 4000 in an amount from about 5% to about 10% by weight of the composition, polysorbate 20 in an amount from about 0.5% to about 2% by weight of the composition, citric acid in an amount from about 0.1% to about 1.0% by weight of the composition, sodium dihydrogen phosphate in an amount from about 0.1% to about 1.0% by weight of the composition, sodium hydroxide in an amount from about 0.1% to about 1.0% by weight of the composition, and has a pH of about 7 to about 7.5. 
     In an additional exemplary embodiment, the pharmaceutical composition comprises paliperidone palmitate in an amount of about 312 mg/mL, polysorbate 20 in an amount of about 10 mg/mL, polyethylene glycol 4000 in an amount of about 75 mg/mL, citric acid in an amount of about 7.5 mg/mL, sodium dihydrogen phosphate in an amount of about 6 mg/mL, sodium hydroxide in an amount 5.4 mg/mL, and has a pH of about 7 to about 7.5. 
     (b) Dosage Forms 
     The physical form of the pharmaceutical composition disclosed herein can and will vary. In general, the pharmaceutical composition can be prepared for parenteral administration. 
     Preparations for parenteral administration may be in a suspension. For parenteral administration (including subcutaneous, intradermal, intramuscular, and intraperitoneal), the preparation may be an aqueous or an oil-based suspension. Aqueous suspensions may include a sterile diluent such as water, saline solution, a pharmaceutically acceptable polyol such as glycerol, propylene glycol, or other synthetic solvents; an antibacterial and/or antifungal agent such as benzyl alcohol, methyl paraben, chlorobutanol, phenol, thimerosal, and the like; an antioxidant such as ascorbic acid or sodium bisulfite citrate; a chelating agent such as etheylenediaminetetraacetic acid; a buffer such as acetate, citrate, or phosphate; and/or an agent for the adjustment of tonicity such as sodium chloride, dextrose, or a polyalcohol such as mannitol or sorbitol. Oil-based suspensions may further comprise sesame, peanut, olive oil, or mineral oil. In an exemplary embodiment, the pharmaceutical composition is formulated as an injectable suspension. 
     Enumerated Embodiments 
     The following enumerated embodiments are presented to illustrate certain aspects of the present invention, and are not intended to limit its scope. 
     1. A process for preparing a micronized paliperidone ester, the process comprising wet milling a suspension comprising a solid paliperidone ester, at least one suspending agent, and at least one wetting agent in the presence of a plurality of polymeric beads to form a micronized paliperidone ester, wherein the polymeric beads have an average diameter from about 0.5 mm to about 1.5 mm, and the micronized paliperidone ester has a particle size distribution from about 1 m to about 30 m. 
     2. The process of enumeration 1, wherein the solid paliperidone ester has an average particle size from about 10 μm to about 200 m. 
     3. The process of enumeration 1 or 2, wherein the solid paliperidone ester is paliperidone palmitate. 
     4. The process of enumeration 3, wherein the solid paliperidone palmitate is added to the suspension in an amount from about 3% to about 60% w/v. 
     5. The process of enumeration 4, wherein the solid paliperidone palmitate is added to the suspension in an amount from about 6% to about 35% w/v. 
     6. The process of any one of enumerations 1 to 5, wherein the at least one suspending agent is chosen from the group consisting of polyethylene glycol, a polypropylene glycol, and combinations thereof. 
     7. The process of enumeration 6, wherein the at least one suspending agent is polyethylene glycol 4000. 
     8. The process of enumeration 7, wherein the polyethylene glycol 4000 is added to suspension in an amount from about 2% to about 30% w/v. 
     9. The process of enumeration 7 or 8, wherein the polyethylene glycol 4000 is added to the suspension in an amount from about 5% to about 20% w/v. 
     10. The process of any one of enumerations 1 to 9, wherein the plurality of polymeric beads consists of polystyrene beads crosslinked with divinylbenzene. 
     11. The process of enumeration 10, wherein the polystyrene beads have an average diameter of about 0.8 mm to about 1.0 mm. 
     12. The process of enumeration 10 or 11, wherein the polystyrene beads have an average diameter of about 0.5 mm. 
     13. The process of any one of enumerations 10 or 11, wherein the polystyrene beads have an average diameter of about 0.6 mm. 
     14. The process of any one of enumerations 10 or 11, wherein the polystyrene beads have an average diameter of about 0.7 mm. 
     15. The process of any one of enumerations 1 to 14, wherein the at least one wetting agent is chosen from the group consisting of polyethylene glycol laurate, glycerol laurate, glycerol stearate, glycerol oleate, polysorbate 20, polysorbate 80, and combinations thereof. 
     16. The process of enumeration 15, wherein the at least one wetting agent is polysorbate 20. 
     17. The process of enumeration 15 or 16, wherein the polysorbate 20 is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     18. The process of any one of enumerations 15 to 17, wherein the polysorbate 20 is added to the suspension in an amount from about 1% to about 3% w/v. 
     19. The process of any one of enumerations 1 to 18, wherein the suspension further comprises at least one buffer. 
     20. The process of enumeration 19, wherein the at least one buffer is chosen from the group consisting of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium acetate, sodium phthalate, and combinations thereof. 
     21. The process of enumeration 20, wherein the at least one buffer is sodium dihydrogen phosphate and disodium hydrogen phosphate. 
     22. The process of enumeration 20 or 21, wherein the at least one buffer is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     23. The process of enumeration 22 wherein the at least one buffer is added to the suspension in an amount from about 0.5% to about 3% w/v. 
     24. The process of any one of enumerations 1 to 23, wherein the suspension further comprises at least one pH modifier. 
     25. The process of enumeration 24, wherein the at least one pH modifier is chosen from hydrochloric acid, citric acid, sodium hydroxide, and combinations thereof. 
     26. The process of enumeration 25, wherein the at least one pH modifier is citric acid and sodium hydroxide. 
     27. The process of enumeration 25 or 26, wherein the at least one pH modifier is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     28. The process of enumeration 27, wherein the at least one pH modifier is added to the suspension in an amount from about 0.5% to about 3% w/v. 
     29. The process of any one of enumerations 1 to 28, wherein the pH of the suspension is from about 6 to about 9. 
     30. The process of enumeration 29, wherein the pH of the suspension is from about 7 to about 7.5. 
     31. The process of any one of enumerations 1 to 30, wherein the micronized paliperidone palmitate has a particle size distribution of dl 0 is from about 2 μm to about 3 μm, d50 is from about 6 μm to about 8 μm, and d90 is from about 15 μm to about 20 m. 
     32. The process of any one of enumerations 1 to 31, wherein the process is conducted aseptically. 
     33. The process of any one of enumerations 1 to 32, wherein the process is carried out as a continuous process. 
     34. The process of any one of enumerations 1 to 33, further comprising formulating the micronized paliperidone ester as an injectable dosage form. 
     35. A process for preparing a micronized paliperidone ester, the process comprising wet milling a suspension comprising a solid paliperidone palmitate, polyethylene glycol 4000, polysorbate 20, sodium dihydrogen phosphate, disodium hydrogen phosphate, citric acid, and sodium hydroxide in the presence of a plurality of polystyrene beads crosslinked with divinylbenzene to form the micronized paliperidone ester, wherein the plurality of polystyrene beads has an average diameter from about 0.5 mm to about 1.5 mm, and the micronized paliperidone ester has a particle size distribution from about 1 μm to about 30 μm 
     36. The process of enumeration 35, wherein the solid paliperidone palmitate is added to the suspension in an amount from about 3% to about 60% w/v. 
     37. The process of enumeration 36, wherein the solid paliperidone palmitate is added to the suspension in an amount from about 6% to about 35% w/v. 
     38. The process of enumeration 35, wherein the polyethylene glycol 4000 is added to suspension in an amount from about 2% to about 30% w/v. 
     39. The process of enumeration 38, wherein the polyethylene glycol 4000 is added to the suspension in an amount from about 5% to about 20% w/v. 
     40. The process of enumeration 35, wherein the plurality of polystyrene beads has an average diameter of about 0.8 mm to about 1.0 mm. 
     41. The process of enumeration 40, wherein the plurality of polystyrene beads has an average diameter of about 0.5 mm. 
     42. The process of enumeration 40, wherein the plurality of polystyrene beads has an average diameter of about 0.6 mm. 
     43. The process of enumeration 40, wherein the plurality of polystyrene beads has an average diameter of about 0.7 mm. 
     44. The process of enumeration 35, wherein the polysorbate 20 is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     45. The process of enumeration 44, wherein the polysorbate 20 is added to the suspension in an amount from about 1% to about 3% w/v. 
     46. The process of enumeration 35, wherein the sodium dihydrogen phosphate is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     47. The process of enumeration 46 wherein the sodium dihydrogen phosphate is added to the suspension in an amount from about 0.3% to about 3% w/v. 
     48. The process of enumeration 35, wherein the citric acid is added to the suspension in an amount from about 0.1% to about 10% w/v. 
     49. The process of enumeration 48, wherein the citric acid is added to the suspension in an amount from about 0.5% to about 3% w/v. 
     50. The process of enumeration 35, wherein the pH of the suspension is from about 6 to about 9. 
     51. The process of enumeration 50, wherein the pH of the suspension is from about 7 to about 7.5. 
     Definitions 
     Compounds useful in the compositions and methods include those described herein in any of their pharmaceutically acceptable forms, including isomers such as diastereomers and enantiomers, salts, solvates, and polymorphs, as well as racemic mixtures and pure isomers of the compounds described herein, where applicable. 
     When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     The term “about,” particularly in reference to a given quantity, is meant to encompass deviations of plus or minus five percent. 
     The term “aseptic,” as used herein, refers to aseptic processing or manufacturing that complies with Good Manufacturing Practice (GMP) industry guidelines such as those associated with Guidance for Industry-Sterile Drug Products Produced by Aseptic Processing-Current Good Manufacturing Practice, U.S. Department of Health and Human Services Food and Drug Administration. 
     EXAMPLES 
     The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples represent techniques discovered by the inventors to function well in the practice of the invention. Those of skill in the art should, however, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention, therefore all matter set forth is to be interpreted as illustrative and not in a limiting sense. 
     Example 1: Preparation of Suspension 
     Polysorbate 20 (8.06 g), PEG 4000 (60.64 g), citric acid monohydrate (6.08 g), sodium dihydrogen phosphate (4.85 g), and sodium hydroxide (4.39 g) were weighed and transferred to a volumetric flask. Water (500 mL) for injection was added to the excipient mixture in a volumetric flask, mixed until completely dissolved, and then filtered. 
     Paliperidone palmitate (63 g) was weighed and transferred to a glass bottle. The filtered excipient solution was added to the paliperidone palmitate and mixed to create a suspension at the targeted milling concentration (6-35 w/v %). The mixture was stirred for an hour to thoroughly wet paliperidone palmitate to produce a homogenous suspension. 
     Example 2: One Step Manufacturing Process 
     The suspension from Example 1 (6-35 w/v %) was milled in a NETZSCH MINICER bead mill using 700 micron polystyrene grinding media (40-85% media load). The mixture was milled at a speed of 3.1-5.5 m/s at 15-25° C. for 20 minutes. 
     Following milling, particle size was measured, in deionized water, using a MALVERN MASTERSIZER 3000 particle size analyzer. The mean milled paliperidone palmitate particle size distribution of the suspension was D90 less than 20 micron, D50 less than 10 micron, and a D10 less than 3 micron ( FIG. 1 ). 
     Example 3: Dissolution Profile on One-Step Milled Particle 
     Paliperidone palmitate release from the milled particles prepared in Example 2 was examined using a USP type 2 apparatus. The release profile is presented in  FIG. 2 .