Spray drying process with continuous preparation of spray solution

Abstract

The present invention discloses a spray drying process characterized by continuous preparation and immediate spray drying of a solution comprising at least one active pharmaceutical ingredient and/or at least one excipient, and at least one solvent. The said active pharmaceutical ingredient(s) and solvent(s) are combined, alone or along with one or more excipients to form a first suspension. Said suspension is continuously fed to an intensifier pump that pushes said suspension through at least one micro-reaction chamber and/or at least one micro-channel where the suspension's solid(s) component(s) is(are) dissolved into said solvent(s) by means of high energy mixing I forced contact at micro, nano and molecular level to form a solution stream. The said solution stream is then immediately and continuously fed to the spray dryer through at least one atomization nozzle, drying said atomized stream to obtain solid particles and collecting said solid particles. Single component particles or multi-component particles, particulate amorphous solid dispersion and pharmaceutical compositions are also disclosed. The present invention also discloses amorphous solid dispersions obtained by the method of the invention as well as pharmaceutical compositions containing the same.

Claims

1. A process for the continuous manufacture of amorphous solid dispersions or API alone particles comprising the steps of: continuously feeding a suspension comprising at least one component and at least one solvent to at least one microfluidization device; mixing the suspension in the microfluidization device by means of micro-reaction or microfluidization to produce a homogeneous spray solution; feeding said spray solution in a continuous mode to a spray dryer; atomizing said spray solution to produce droplets using at least one atomization nozzle; and drying said droplets in a drying chamber to obtain particles.

2. The process according to claim 1, wherein the suspension is prepared by mixing in a continuous or discontinuous mode at least one component with at least one solvent.

3. The process according to claim 1, wherein the at least one component comprises at least one active pharmaceutical ingredient (API), at least one excipient, or a combination of an API and an excipient.

4. The process according to claim 3, wherein the active pharmaceutical ingredient and/or the excipient has low solubility, low dissolution kinetics or poor stability in solution.

5. The process according to claim 3, wherein the at least one excipient is selected from the group consisting of: polymers, surfactants, sugars, amino acids, chitin, chitosan, alginates, polysaccharides, and combinations thereof.

6. The process according to claim 1, wherein the solvent is selected from the group comprising: water, methanol, ethanol, propanol, acetone, butanone, tetrahydrofuran, dichloromethane, hexane, DMSO, ethyl acetate, n-heptane and combinations thereof.

7. The process according to claim 1, wherein the microfluidization is effected using at least one microreactor and/or at least one micro-chamber.

8. The process according to claim 1, wherein the microfluidization is effected using at least one microreactor and/or at least one micro-chamber, which operates in a recirculation mode.

9. The process according to claim 7, wherein the microreactor is a continuous flow reactor.

10. The process according to claim 7, wherein the at least one microreactor or microchamber comprises one or more channels, optionally wherein the number of channels are in the range of about 1 to about 10.

11. The process according to claim 7, wherein the at least one microreactor or microchamber comprises one or more channels each having a diameter in the range of about 10 microns to about 1000 microns or in the range of about 50 microns to about 400 microns.

12. The process according to claim 1, wherein the microfluidization is effected using more than one microreactor, and wherein the microreactors are arranged in series or in parallel.

13. The process according to claim 12, wherein the number of microreactors arranged in series or in parallel ranges from about 1 to about 10.

14. The process according to claim 1, wherein the suspension comprising the component and the solvent is fed to the microreactor/microchamber using at least one pump, optionally wherein the pump comprises an intensifier pump.

15. The process according to claim 1, wherein the suspension is prepared by dispersing in a continuous or discontinuous mode at least one component in at least one solvent in a buffer tank and the suspension from the buffer tank is fed to the microreactor/microchamber using at least one pump, optionally wherein the pump comprises an intensifier pump.

16. The process according to claim 7, wherein the suspension is fed to the microreactor/microchamber at a pressure in range of about 1 bar to about 3500 bar or in the range of about from 1 to about 2000 bar.

17. The process according to claim 7, wherein the suspension comprising the component and the solvent is mixed in the one or more channels of microreactor/microchamber such that the particle size of the component is reduced by micronization.

18. The process according to claim 7, wherein the suspension comprising the component and the solvent is mixed in the one or more channels of microreactor/microchamber such that heat is generated.

19. The process according to claim 1, wherein said spray solution from the microfluidization device is delivered to a buffer tank.

20. The process according claim 1, wherein said spray solution from the microfluidization device is recirculated to a first buffer tank in which a stream comprising the at least one component and a stream comprising the at least one solvent are combined.

21. The process according to claim 20, wherein the solution from the first buffer tank is transported to a second buffer tank, optionally wherein the solution from the second buffer tank is continuously fed to the spray dryer.

22. The process according to claim 1, wherein said spray solution is continuously fed to the spray dryer using at least one pump, optionally wherein the pump comprises an intensifier pump.

23. The process according to claim 1, wherein the at least one atomization nozzle is selected from the group comprising: a two fluid nozzle, a pressure nozzle, a rotary nozzle, an ultrasonic nozzle and combinations thereof.

24. The process according to claim 1, wherein the droplets formed from the spray solution ranges from about 1 to 200 μm, preferably in the range of about from 30 to 80 μm.

25. The process according to claim 1, wherein the spray solution is fed to said atomization nozzle at a hydrodynamic pressure in the range of from about 1 to about 200 bar or in the range of 10 to about 100 bar.

26. The process according to claim 1, wherein the droplets are dried in the drying chamber using a gas, optionally the gas comprises nitrogen, air, carbon dioxide or a combination thereof.

27. The process according to claim 1, wherein the drying gas when entering the drying chamber has a temperature in the range of from about −20 to about 200° C. or in the range of from about −10 to about 100° C.

28. The process according to claim 1, wherein the temperature of the drying gas exiting the drying chamber is lower than the temperature of the gas when entering the drying chamber.

29. The process according to claim 1, wherein the drying gas is recycled to the drying chamber after passing through a condenser.

30. The process according to claim 1, further comprising drying the spray dried particles in a secondary drying discontinuous operation, wherein optionally the secondary drying discontinuous operation includes: reducing pressure below room pressure, heating above room temperature or agitation.

31. The process according to claim 3, wherein the at least one excipient is a cellulosic polysaccharide or derivatives thereof.

32. The process according to claim 3, wherein the at least one excipient is a polymer with a vinyl group or a polymer with an acrylic or derivatives thereof.

33. The process according to claim 32, wherein the polymer with the vinyl group comprises poly vinyl pirrolidone, or wherein the polymer with the acrylic or derivatives thereof comprises poly methyl acrylic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows a schematic representation of the process steps as per the state-of-the-art.

(2) FIG. 1B shows a schematic representation of the process steps as per the present invention disclosure.

(3) FIG. 2A is a schematic representation of an embodiment of the system of the present invention.

(4) FIG. 2B is a schematic representation of an embodiment of the system of the present invention.

(5) FIG. 2C is a schematic representation of an embodiment of the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(6) The present invention discloses a continuous spray drying method characterized by continuous preparation and spray drying of a spray solution comprising at least one active pharmaceutical ingredient or at least one excipients or a combination of one or more APIs and excipients, and at least one solvent.

(7) Referring now to the invention in more detail, in FIG. 2A it is shown a system comprising an optional buffer tank which receives at least one solvent stream (1) and at least one solid stream (2); a pump (3); a microfluidization apparatus/device (4); an optional buffer tank; a spray dryer comprising a drying camber (5) and means for recovering the dried particles (7).

(8) Preferably, the solvent stream (1) and the solid stream (2) are fed to a buffer tank (2) and combined either discontinuously or continuously, preferably at individually controlled rates to form a suspension.

(9) Preferably, the buffer tank is connected to a pump (3) which may in turn be connected to the microfluidization apparatus (4). The pump (3) comprises an intensifier pump or any pump known to a person skilled in the art suitable for pumping the suspension in the buffer tank at pressure sufficient to continuously transport the suspension to the microfluidization apparatus (4).

(10) Preferably, the microfluidization apparatus (4) comprises one or more microreactors and/or micro-channels. Preferably, the microfluidization apparatus (4) is operated in a recirculation mode.

(11) Preferably, the reaction chamber in the micro-reactor comprises one or more channels of well-defined diameter and size. Preferably, the diameter of the channels is the range of about 10 to about 1000 um or about 10 micron to about 400 microns. More preferably, the diameter is in the range of about 50 microns to about 200 microns. The micro-channels may also have a diameter ranging from 1 to 10 um or 1 to 5 um.

(12) The number of micro-channels and/or micro-reactors used in the present invention is not limited, but preferably ranges from 1 to 10. In embodiments using more than one micro-reactor, the micro-reactors may be arranged in series or in parallel.

(13) The microfluidization apparatus facilitates further mixing and micronization of the particles in the suspension to form a homogenous spray solution. The microfluidization apparatus also facilitates heat generation or increase in temperature which increases the solubility of the solids in the suspension.

(14) The microfluidization apparatus is connected to a spray drying unit (5). Preferably, the microfluidization apparatus is connected to the spray drying unit (5) via a buffer tank.

(15) Preferably, a buffer tank is used to discharge the homogenous spray solution from the microfluidization apparatus prior to being fed to the spray dryer (5).

(16) Preferably, an intensifier pump is used to continuously transport the spray solution from the buffer tank or the microfluidization apparatus to an atomizer in the spray dryer for drying and separating the solid particles.

(17) Preferably, the microfluidization apparatus operates in a recirculation mode. The microfluidization apparatus may be connected to the buffer tank in which the at least one component and the at least one solvent are combined, to recirculate the solution from microfluidization apparatus until the desired solids dissolution is achieved. Preferably, the system provides a second buffer tank connected to the first buffer tank for receiving multiple batches of solution from the first buffer tank in a semi-continuous mode, such that the solution from the second buffer tank is continuously fed to the spray dryer.

(18) In an embodiment of the present invention, a spray drying unit is used for drying and recovering the solid material from the suspension. The spray drying unit may be any suitable spray drying device known in the art. Preferably, the spray drying apparatus comprises a spray drying chamber (5) where the solution from the microfluidization apparatus (4) in the form of a liquid stream is continuously fed using an atomization nozzle to form droplets and dried with drying gas (6).

(19) The spray drying apparatus also comprises means for recovering the dried particles from the spray dryer chamber. In FIG. 2A, the dried particles are separated from the drying gas in a cyclone (7) and collected in an outlet stream (9), while the drying gas exits the cyclone (7) in an outlet stream (8). However, the means for recovering dried particles from the spray dryer chamber may also take the form of other means, which will be known to the person skilled in the art, such as a filter bag.

(20) FIG. 1A shows a diagram of the method of prior art. In the state of the art the spray solution is prepared by first milling the solids (APIs) in a discontinuous process and then a stream of the milled solids and a stream of solvent are fed to a stirred tank in which the solids are dissolved in the solvent by stirring and mixing over a period of time. If needed, heat from the external source may also be applied during the mixing step. The resulting suspension is then subjected to a spray drying process to obtain solids particles. FIG. 1B shows a diagram of the method of the present invention

(21) In a preferred embodiment of the present invention, a stream comprising at least one solvent (1) and a stream comprising at least one solids (2) are combined discontinuously or continuously at individually controlled rates to form a suspension. Preferably, the stream comprising the solids and the stream comprising the solvent are fed to a buffer tank. In a preferred embodiment, the mixing of solvent stream and solid stream occurs under controlled conditions in order to promote dispersion of the solid stream into the solvent stream. Preferably, a buffer and/or a static mixer are used to combine the solid and solvent stream to form the suspension. Preferably, the solid and solvent stream are combined at a ratio at which the solid is within the solubility limit in the solvent system and is in the range of, but not limited to, about 1% to about 50% (w/w) or about 5% to about 15%. The ratio between solvent and solid may also be optimized to control particle characteristics after spray drying (e.g. particle size and density).

(22) Preferably, the suspension is continuously fed to one or more intensifier pumps (3) at a controlled rate which depends for example on the characteristics of the suspension. Then, the suspension is pressurized with the one or more intensifier pumps (3) to one or more micro-reactor (4), causing the components of the suspension to interact at micro, nano and molecular level resulting in a homogeneous spray solution. The microreactor facilitates highly effective molecular contact/interaction of the components of the suspension within a defined reaction chamber and/or micro channel, resulting in solids micronization and high energy mixing which ultimately results in improved dissolution kinetics and solubility.

(23) Preferably, the suspension comprises of at least one solvent, at least one active pharmaceutical ingredient and/or at least one excipient. Preferably, the least one active pharmaceutical ingredient and/or the excipient has poor stability in solution, low solubility and/or low dissolution kinetics properties.

(24) In a preferred embodiment, the process pressure and solids concentration in the suspension can be optimized to promote micro-reaction such that the dissolution of the solids in the suspension is increased.

(25) In a preferred embodiment, the suspension is fed to the microreactor/microchannel at a pressure sufficient to form a homogenous spray solution.

(26) The pressure may be in the range of from about 1 bar to about 3500 bar, preferably from about 20 to about 3500 bar, more preferably from about 100 to about 3000 bar, or from about 300 bar to about 2500 bar. Preferably, the pressure may also be in the range of from about 1 bar to about 2000 bar or 10 to 1500 bar.

(27) It is also disclosed that during the mixing step in the micro-reactor the suspension, is preferably fed at a temperature Tin, may experience a temperature increase up to Tout as a result of the high energy interactions. The difference between Tin and Tout depends on the operating conditions and on the properties of the suspension stream. Preferably, the solids are soluble in the solvent within the range comprised between Tin and Tout. Tin and Tout may be controlled by external energy input to control degradation, solubility and dissolution kinetics.

(28) The temperature Tin may be in the range of from about −10° C. to 100° C., preferably in the range of −5° C. to 80° C.

(29) The temperature Tout may be in the range of from about 0° C. and 150° C., preferably in the range of 5° C. to 130° C.

(30) Preferably, the spray suspension is pumped into a series of micro-reactors/micro-channels having at least about 1 to 10 micro-reactors or micro-channels.

(31) Preferably, the homogenous spray solution formed in the microreactor is continuously fed to a spray dryer using a pump such as an intensifier pump or any pump suitable for transporting the spray solution to the spray dryer (5).

(32) Preferably, the spray solution from the micro-reactor or microfluidization apparatus is immediately and continuously fed to the spray dryer.

(33) Preferably, a buffer tank is used to discharge, continuously or discontinuously, the homogenous spray solution prior to being fed to the spray dryer (5). An intensifier pump may be used to transport the spray solution to the atomizer of the spray dryer.

(34) In a preferred embodiment, connecting means/apparatus are provided for connecting the micro-reactors or micro-channels to a buffer tank, which in turn is connected to a spray drying apparatus.

(35) In a preferred embodiment, FIG. 2B shows means or an apparatus having a solvent stream (1) and solid stream (2) which are connected to a buffer tank (10), which in turn may be connected to an intensifier pump (3). The intensifier pump (3) is connected to micro-reactors/micro-channels (4) and these components (i.e. the unit comprising the apparatus comprising solvent and solid streams, buffer tank, pump and microreactor) are connected to a spray drying apparatus (5).

(36) In another preferred embodiment, FIG. 2C shows a solids stream (11) and a solvent stream (12) being discharged into a first buffer tank (13), continuously or discontinuously. The solution or suspension comprising the solids and solvent in the buffer tank (13) is transported to micro-reactors/micro-channels (not shown), preferably using an intensifier pump (14). The solution or the suspension from the micro-reactors/micro-channels may be recirculated back to the buffer tank (12) until the desired solids dissolution is achieved. In a semi-continuous mode the solution from the buffer tank (12) may be transferred to a second buffer tank (15) which in turn is connected to a spray drying apparatus comprising a spray drying chamber (16). Preferably, in a semi-continuous mode multiple batches of the solution can be prepared in the first buffer tank (13). The multiple batches of solution in the first buffer tank (13) may be transferred to the second buffer tank (15), continuously or discontinuously, such that the solution is not exhausted in the second buffer tank (15), while the spray drying process is operating in a continuous mode. Preferably, the solution from the second buffer tank (15) is continuously fed to a spray drying chamber (16) using an atomization nozzle to form droplets and dried with drying gas (17). The spray drying apparatus also comprises means (19) for recovering the dried particles (20) from the spray dryer chamber (16), while the drying gas exits in an outlet stream (18).

(37) In the present invention it is also disclosed that the spray solution is continuously fed to at least one atomizer that atomizes the spray solution into droplets inside a drying chamber (5) where the solvent is evaporated by the effect of a drying gas, forming a spray dried particles stream (9) that is collected on a cyclone or filter bag (7) installed at the outlet of the drying chamber (5).

(38) Atomization can be promoted using specific types of atomizers such as, but not limited to, rotary nozzles, pressure nozzles, two fluid nozzles, ultrasonic nozzles or any other device capable of atomizing a solution, or preferentially, any device capable of forming droplets from a solution. Preferably, the atomization conditions and spray drying process parameters can be optimized to manufacture the desired particles. More preferably, a pressure nozzle is used, which is capable of atomizing the spray solution at hydrodynamic pressures ranging from about 1 to about 200 bar or about 10 to about 100 bar. The droplets formed in the present invention are preferably in the range of from about 1 micron to about 1000 micron, preferably between 1 micron to 200 microns, preferably between 30 microns to 200 microns or 30 microns to 80 microns.

(39) The spray solution that is continuously fed through the atomizer to the spray drying chamber may comprise at least one dissolved active pharmaceutical ingredient and at least one solvent, alone or along with one or more excipients.

(40) More specifically, the excipient(s) may be selected from the group comprising: polymers, surfactants, surface modifiers, sugars, amino acids, polysaccharides, for example, a cellulosic polysaccharide or derivative/cellulose-based polymers, chitin and chitosan, alginates or other polymer groups such as vinyl polymers, for example poly vinyl pirrolidone, or polymers with acrylic groups for example poly methyl acrylic, and any other polymer and combinations thereof.

(41) The solvent used in preparing the spray solution may be selected from the group comprising: water, methanol, ethanol, propanol, acetone, butanone, tetrahydrofuran, dichloromethane, hexane, ethyl acetate, n-heptane, other organic solvents and combinations thereof.

(42) Preferably, a pH adjusting agent such as sodium hydroxide, hydrochloric acid, tris buffer or citrate, acetate, lactate, meglumine, or the like is added to the “solvent” solution. Preferably, the temperature of the solvent may be adjusted. Preferably, the temperature is adjusted in the range of about −20 to 70° C. However, based on the substance or component which is dispersed in the solvent, a person skilled in the art can adjust the temperature suitably.

(43) Preferably, the atomization conditions and spray drying process parameters can be optimized to manufacture the desired particles.

(44) Preferably, the drying gas stream (6) comprises air, nitrogen or carbon-di-oxide. Preferably the drying gas is fed at a flow rate and at a temperature that are sufficient to evaporate the solvent(s) from the atomized spray solution up to an extent that solid particles are formed. Preferably, the drying gas flow rate ranges from 0.1 kg/h to 5000 kg/h, more preferably the drying gas flow rate ranges from 1 kg/h to 2000 kg/h. Preferably, the drying gas temperature ranges from about −20° C. to about 200° C., more preferably in the range of from −10° C. to 100° C. The drying gas can be recycled through a condenser unit to condensate most of the solvent. The condensed liquid is then pumped and the gas is heated to temperatures ranging from about −20° C. to about 200° C. before re-entering the drying chamber. The condenser unit typically operates at temperatures ranging from about −20° C. to about 30° C.

(45) The spray drying chamber (7) has enough volume to allow the contact between the atomized spray solution and the drying gas being fed at individually controlled flow rates. Preferably, the spray drying chamber has enough volume to allow the contact between the atomized spray solution and the drying gas and to allow the evaporation of the solvent(s) from the atomized spray solution up to an extent that solid particles are formed.

(46) Preferably, the spray dried material is further dried in a secondary drying discontinuous operation using at least one of the following means: by reducing pressure below room pressure, heating above room temperature or by agitation.

(47) In the present invention, spray solutions are prepared using high shear mixing in the apparatus such as in micro-channels and/or micro-reactors. Such high shear mixing allows for faster dissolution kinetics and enhanced solubility as a result of increased surface area of the drugs and/or excipients particles by particle size reduction and local heat generation of the spray solution which spontaneously increases the temperature.

(48) Furthermore, in the process of the present invention, microfluidization is effected by using an apparatus such as micro-channels and/or micro-reactors to promote micronization and to improve solids dissolution kinetics and solubility. In the present invention a suspension comprising at least one solid component and at least one solvent may be micronized by microfluidization in order to obtain a homogeneous spray solution. The resulting homogeneous spray solution may then be spray dried to remove the solvents resulting in solid particles.

(49) In a preferred embodiment of the present invention only one stream of a suspension comprising at least one solid component and at least one solvent is used for preparing a spray solution. The single stream of suspension is continuously fed to a micro reactor and then to a spray-dryer to obtain solid material particles.

(50) Furthermore, in a preferred embodiment of the present invention, there is no need for a filtration system for concentrating the spray solution obtained from the micro reactor prior to feeding the solution to a spray dryer. Also, in a preferred embodiment of the present invention, there is no need to subject the solid stream to milling process. As a result, the process of the present invention is simple, more efficient requiring less equipment for carrying out the process with no hold time in view of faster/quicker dissolution of the solids in the suspension.

(51) The advantages of the present invention include, without limitation: it aids in reducing particle size of the solids in a suspension by micronization; increases or enhances the dissolution kinetics and solubility of low soluble solids, such as APIs and excipients. enables increase in temperature during micronization process without the need for any external heat energy source; enables an efficient process as no additional batch operation is required to prepare the spray solution; provides a process in which batch size is not limited by the feed tank capacity; low or no hold time between solution preparation and spray drying eliminating potential spray solution stability issues associated, particularly in relation to low soluble solids such as drug active material and excipients; provides continuous preparation of a spray solution; provides a continuous method of preparing solid particles; provides a method which is easily scalable.

(52) The present disclosure provides a process for continuous drying a spray solution wherein said spray solution is formed by feeding at least one solid active pharmaceutical ingredient and/or at least one pharmaceutical excipient to at least one solvent forming a spray suspension that is fed to a micro-reactors or micro-channels system and continuously form a spray solution that is continuously fed to a nozzle that disperses said spray solution into droplets inside a drying chamber where a drying gas evaporates the solvents from each droplet forming solid particles that are collected on a cyclone.

(53) Disclosed herein is a method for manufacturing single component particles and/or multi-component particles comprising the steps of: Mixing, in a continuous or discontinuous mode, of at least one active pharmaceutical ingredient with at least one solvent, alone or along with one or more excipients to form a suspension; Continuous feeding of said suspension to an intensifier pump which in turn continuously feeds the suspension to at least one micro-reactor and/or at least one micro-chamber; High energy mixing of said suspension in said micro-reactor(s) and/or micro-chamber(s) by means of micro-reaction or microfluidization to produce a homogeneous spray solution stream; Continuous feeding of said spray solution to a spray dryer; Atomizing the said spray solution stream using at least one atomization nozzle to produce droplets stream; Drying the said droplets stream in the drying chamber to obtain solid particles; and Collecting said solid particles.

(54) The present invention also provides a system for continuous preparation of solid particles.

(55) The present invention also provides for a process for continuous preparation of solid particles using the system of the present invention. The present invention also provides a product obtained by the process for continuous preparation of solid particles using the system of the present invention.

(56) Preferably, in the present invention only one stream of suspension is used and is continuously fed to a spray-dryer to obtain a solid material in the end of the process.

(57) The present invention also provides a pharmaceutical composition comprising the solid particles obtained by the process of the present invention using the system according to the present invention. The pharmaceutical composition is used as a medicine. Preferably the solid particles comprises single component particles, multi-component particles in amorphous or crystalline form (co-crystals) and amorphous solid dispersions, preferably having particle sizes in the micro- and/or nano-range.

(58) The present invention also provides use of at least one microreactor and/or at least one micro-chamber for micronization of particles in a suspension comprising at least one component and at least one solvent in a process for the continuous manufacture of single component particles and/or multi-component particles. The at least one component may be an active pharmaceutical ingredient and/or an excipient having poor stability in solution, low solubility and/or low dissolution kinetics properties.

(59) While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.

EXAMPLES

(60) Suitable examples, which are meant only to suggest a method of practicing the present invention and do not serve to limit the scope of the present invention, follows:

Example 1

(61) Polyvinylpyrrolidone vinyl acetate (PVP/VA, 11.9 g) was added to water (467.3 g) at room temperature in a buffer tank under stirring to prepare a suspension with 2.5% w/w solids load. The resulting suspension was continuously passed through a series of five micro-reactors with microchannels having 500 micron diameter by means of an intensifier pump (MicroDeBEE) at a pressure of 1862 bar. After one single passage of the suspension through the series of five micro-reactors a homogeneous solution was obtained.

(62) For comparison purposes, a PVP/VA (5.0 g) was mixed with water (203.6 g) at room temperature in a stirred vessel. Complete dissolution of PVP/VA was achieved after 1 h12 m.

(63) The same experiment was repeated with the same setup for other pharmaceutical excipients and solvents. Trihalose is crystalline form and was used as a model for crystalline molecules to mimic API's. The obtained results are summarized in the Table 1 below.

(64) TABLE-US-00001 TABLE I Stirred tank dissolution at room temperature Continuous solution preparation time for Formulation Solids Solvent Concentration Continuous Solid Solvent Concentration dissolution Solid Solvent (g) (g) (% wt) dissolution (g) (g) (% wt) (hh:mm) PVP/VA Water 11.9 467.3 2.5 YES 5.0 203.6 2.4 01:12 Ethanol 4.25 180.2 2.4 YES — — — Not tested Ethanol 7.95 181.1 4.2 YES — — — Not tested Poloxamer Ethanol 10.55 411.6 2.5 YES 5.12 200.5 2.5 00:06 188 Ethanol 13.67 333.8 3.9 YES — — — Not tested L-Leucine H2O 1.38 451.2 0.3 YES 1.34 461.3 0.3 00:48 L-Leucine + H2O 1.58 + 3.42 450 1.1% (32% L- YES 0.71 + 1.65 203.2 1.1 00:10 Trehalose Leuc + 68% Trehalose)

(65) It can be seen from test results that dissolution of the solid particles takes place immediately or within few seconds (i.e. continuous dissolution) in the continuous solution preparation of the present invention whereas in the stirred tank dissolution as per the state-of-the-art the time taken for dissolution of particles range from 10 minutes to 1.12 hrs. Thus, the test results demonstrate that spray solution can be prepared continuously by the process of the present invention, in a time period of few seconds. When compared to stirred vessel dissolution, the increase in the dissolution kinetics may be explained as a result of micronization and high shear mixing effects inside the micro-reactors.