Bupivacaine microspheres and preparation method thereof

Abstract

The invention provides a preparation method of bupivacaine microspheres, which comprises the following steps: mixing bupivacaine alkali, PLGA (poly (lactic-co-glycolic acid)) and an organic solvent to prepare an oil phase; mixing polyvinyl alcohol with water to prepare a water phase; mixing the oil phase and the water phase, emulsifying, curing, and washing to prepare wet pellets; freezing and drying the wet balls to prepare bupivacaine microspheres; wherein the freeze drying process sequentially comprises four stages of pre-freezing, first-stage drying, second-stage drying and temperature returning; the conditions of the first-stage drying are as follows: the temperature is-12 DEG C to-10 DEG C, and the vacuum degree is 0.4 mbar to 0.6 mbar; the conditions of the second-stage drying are as follows: the temperature is 32 DEG C to 38 DEG C, and the vacuum degree is 0.4 mbar to 0.6 mbar. The bupivacaine microspheres obtained by the preparation method are quickly released in the early stage of administration, and then are slowly and stably released in the curative effect time, and the microspheres are large in particle size and can be collected through simple vibration screening.

Description

Technical Field

[0001] The present invention relates to the technical field of pharmaceutical preparations, and particularly to a bupivacaine microsphere and a preparation method thereof. Background Art

[0002] A microsphere is a long-acting preparation. The drug is embedded or adsorbed on the surface or inside of the polymer. After being injected into the body, the polymer slowly erodes and degrades, and the encapsulated drug diffuses accordingly. The drug is slowly released at a certain rate per unit time to maintain a stable blood drug concentration.

[0003] Bupivacaine is a commonly used amide local anesthetic in clinical practice. It has the characteristics of strong anesthetic effect and long action time, and is widely used in spinal anesthesia, epidural anesthesia, brachial plexus block, and the treatment of postoperative anesthetic pain and some long-term severe and cancer pain. A local anesthetic needs to slowly and stably release the drug within the efficacy time to maintain the drug concentration continuously to achieve the analgesic effect. If the drug release is too fast, it will not be sufficient to cover the pain interval. If the drug release is too slow, there will be over-treatment and even safety risks. At the same time, because the patient is in pain in the initial stage after surgery, the local anesthetic also needs to meet the requirement of rapid release in the early stage of administration. Therefore, the clinical requirements for bupivacaine microsphere preparations are relatively high.

[0004] Currently, it is found that by reducing the microsphere particle size and shortening the drug migration channel, the rapid release of the drug in the early stage can be accelerated. However, at the same time, due to the small particle size, it cannot be collected by the conventional oscillating screening method, which increases the equipment and production costs. There is also a traditional technology that adds a pore-forming agent and disperses it in the carrier material to form a porous structure on the surface of the microsphere, thereby increasing the drug migration rate and achieving the purpose of accelerating the early release of the drug. However, this method requires a full investigation of the interaction between the selected pore-forming agent type and the microsphere raw materials and excipients, and increasing the types of excipients in the prescription will also lead to an increase in production costs. Summary of the Invention

[0005] Based on this, the present invention provides a preparation method of a bupivacaine microsphere. The bupivacaine microsphere obtained by this preparation method has a fast release in the early stage of administration, and then slowly and stably releases within the efficacy time. Moreover, the bupivacaine microsphere prepared by this preparation method has a relatively large particle size and can be collected by simple oscillating screening.

[0006] The present invention is realized through the following technical solutions.

[0007] A preparation method of a bupivacaine microsphere includes the following steps:

[0008] Mix bupivacaine base, PLGA and an organic solvent to prepare an oil phase;

[0009] Mix polyvinyl alcohol and water to prepare an aqueous phase;

[0010] Mix the oil phase with the water phase, emulsify, then solidify, and then wash to prepare wet microspheres;

[0011] Lyophilize the wet microspheres to prepare bupivacaine microspheres;

[0012] Among them, the lyophilization process successively passes through four stages: pre-freezing, primary drying, secondary drying, and rewarming; the conditions for the primary drying include: the temperature is -12°C to -10°C, and the vacuum degree is 0.4 mbar to 0.6 mbar; the conditions for the secondary drying include: the temperature is 32°C to 38°C, and the vacuum degree is 0.4 mbar to 0.6 mbar.

[0013] In one embodiment, the conditions for the pre-freezing include: the temperature is -35°C to -25°C.

[0014] In one embodiment, the conditions for the rewarming include: the temperature is 15°C to 25°C.

[0015] In one embodiment, the conditions for emulsification include: the rotation speed is 1200 rpm to 2500 rpm.

[0016] In one embodiment, in the PLGA, the molar ratio of LA to GA is 50:50.

[0017] In one embodiment, the organic solvent is dichloromethane.

[0018] In one embodiment, the oil phase satisfies one or more of the following conditions:

[0019] (1) The mass ratio of bupivacaine base to PLGA is 1:1;

[0020] (2) In the oil phase, the total mass concentration of bupivacaine base and PLGA is (0.25 - 0.5) g / mL;

[0021] (3) The volume ratio of the oil phase to the water phase is 1:(140 - 160).

[0022] In one embodiment, in the water phase, the mass concentration of polyvinyl alcohol is (0.005 - 0.01) g / mL.

[0023] In one embodiment, the conditions for solidification include: at a rotation speed of 140 rpm to 180 rpm, first stir at a temperature of 18°C to 22°C for 0.8 h to 1.2 h, and then stir at a temperature of 33°C to 37°C for 3.3 h to 3.7 h.

[0024] The present invention also provides bupivacaine microspheres prepared by the preparation method as described above.

[0025] Compared with the prior art, the preparation method of the bupivacaine microspheres of the present invention has the following beneficial effects:

[0026] By defining the process procedures of freeze-drying, specifically including four stages of pre-freezing, primary drying, secondary drying and rewarming in sequence, and further defining the temperature and vacuum degree in the primary drying and secondary drying stages, the prepared bupivacaine microspheres can not only meet the rapid release in the early stage of drug administration, slowly and stably release during the whole curative effect time, keep the drug concentration continuously reaching the analgesic effect, but also have relatively large particle size of the obtained bupivacaine microspheres, and can be collected by simple oscillating sieving, thereby reducing the production cost.

[0027] Furthermore, the preparation method of the present invention can achieve the purpose of rapid release in the early stage of drug administration without adding pore-forming excipients, reduces the risk of weakened drug efficacy caused by the interaction between components to a certain extent, and also controls the cost of raw materials and excipients. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the release curve graph of Examples 1 to 3 provided by the present invention;

[0029] Figure 2 It is the scanning electron microscope image of the bupivacaine microspheres of Example 1 provided by the present invention;

[0030] Figure 3 It is the scanning electron microscope image of the cut bupivacaine microspheres of Example 1 provided by the present invention;

[0031] Figure 4 It is the release curve graph of Comparative Examples 1 to 2 provided by the present invention;

[0032] Figure 5 It is the scanning electron microscope image of the bupivacaine microspheres of Comparative Example 1 provided by the present invention;

[0033] Figure 6 It is the scanning electron microscope image of the cut bupivacaine microspheres of Comparative Example 1 provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to related embodiments. Preferred embodiments of the present invention are given in the embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the understanding of the disclosure of the present invention is more thorough and comprehensive.

[0035] The terms "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same cases or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

[0036] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as every value therebetween. Further, when the range refers to integers, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0037] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the composition of the present invention. Unless otherwise specified, all masses of the listed components refer to the content of the active substance, and thus they do not include solvents or by-products that may be contained in commercially available materials. The term "mass percentage content" in this text can be represented by the symbol "%". Unless otherwise specified, all molecular weights in this text are weight-average molecular weights expressed in daltons. Unless otherwise specified, all formulations and tests occur in an environment of 25 °C. The terms "comprise", "include", "contain", "have" or other variants in this text are intended to cover non-closed inclusion, and no distinction is made between these terms. The term "include" means that other steps and components can be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional components, ingredients, steps, or limitations described herein. No distinction is made between the terms "efficacy", "performance", "effect", and "efficiency" in this text.

[0038] The weights of the relevant components mentioned in the description of the embodiments of the present invention can not only refer to the specific contents of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the description of the embodiments of the present invention are scaled up or down in proportion, they are within the scope disclosed in the description of the embodiments of the present invention. Specifically, the weights described in the description of the embodiments of the present invention can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0040] PLGA, a copolymer of polylactic acid and glycolic acid, is a biodegradable material. Its main chain contains chemical bonds that are unstable and easily hydrolyzed or enzymatically degraded. In vivo, it hydrolyzes and defats to generate lactic acid monomers, which are oxidized to pyruvic acid under the action of lactate dehydrogenase and participate in the body's tricarboxylic acid cycle as energy metabolism substances. The end products are water and carbon dioxide, which are excreted through the lungs, kidneys, and skin. The molar ratio of PLGA is expressed by the number of moles of lactic acid (LA) and glycolic acid (GA).

[0041] The present invention provides a method for preparing bupivacaine microspheres, which comprises the following steps:

[0042] Mix bupivacaine base, PLGA and an organic solvent to prepare an oil phase;

[0043] Mix polyvinyl alcohol and water to prepare an aqueous phase;

[0044] Mix the oil phase and the aqueous phase, emulsify, then solidify, and then wash to prepare wet microspheres;

[0045] Lyophilize the wet microspheres to prepare bupivacaine microspheres;

[0046] Wherein, the lyophilization process successively passes through four stages: pre-freezing, primary drying, secondary drying and rewarming; the conditions for primary drying include: temperature is -12°C to -10°C, and vacuum degree is 0.4 mbar to 0.6 mbar; the conditions for secondary drying include: temperature is 32°C to 38°C, and vacuum degree is 0.4 mbar to 0.6 mbar.

[0047] It can be understood that in the present invention, the temperature for primary drying includes but is not limited to -12°C, -11.5°C, -11°C, -10.5°C, -10°C. In a more specific example, the temperature for primary drying is -11.5°C to -10.5°C.

[0048] It can be understood that in the present invention, the vacuum degree for primary drying includes but is not limited to 0.4 mbar, 0.45 mbar, 0.5 mbar, 0.55 mbar, 0.6 mbar. In a more specific example, the vacuum degree for primary drying is 0.45 mbar to 0.55 mbar.

[0049] In a specific example, the conditions for the first-stage drying further include: the time is 4 h to 8 h. It can be understood that in the present invention, the time for the first-stage drying includes but is not limited to 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.1 h, 6.2 h, 6.3 h, 6.4 h, 6.5 h, 6.6 h, 6.7 h, 6.8 h, 6.9 h, 7 h, 7.5 h, 8 h. In a more specific example, the time for the first-stage drying is 5.5 h to 7 h.

[0050] It can be understood that in the present invention, the temperature for the second-stage drying includes but is not limited to 32 °C, 33 °C, 34 °C, 34.5 °C, 35 °C, 35.5 °C, 36 °C, 37 °C, 38 °C. In a more specific example, the temperature for the second-stage drying is 34 °C to 36 °C.

[0051] It can be understood that in the present invention, the vacuum degree for the second-stage drying includes but is not limited to 0.4 mbar, 0.45 mbar, 0.5 mbar, 0.55 mbar, 0.6 mbar. In a more specific example, the vacuum degree for the second-stage drying is 0.45 mbar to 0.55 mbar.

[0052] In a specific example, the conditions for the second-stage drying further include: the time is 50 h to 60 h. It can be understood that in the present invention, the time for the second-stage drying includes but is not limited to 50 h, 51 h, 52 h, 52.5 h, 53 h, 53.5 h, 54 h, 54.5 h, 55 h, 56 h, 57 h, 58 h, 59 h, 60 h. In a more specific example, the time for the second-stage drying is 52 h to 55 h.

[0053] In a specific example, the conditions for pre-freezing include: the temperature is -35 °C to -25 °C. It can be understood that in the present invention, the temperature for pre-freezing includes but is not limited to -35 °C, -34 °C, -33 °C, -32 °C, -31 °C, -30 °C, -29 °C, -28 °C, -27 °C, -26 °C, -25 °C. In a more specific example, the temperature for pre-freezing is -32 °C to -28 °C.

[0054] In a specific example, the conditions for pre-freezing further include: the time is 2 h to 4 h. It can be understood that in the present invention, the time for pre-freezing includes but is not limited to 2 h, 2.5 h, 3 h, 3.5 h, 4 h. In a more specific example, the time for pre-freezing is 2.5 h to 3.5 h.

[0055] In a specific example, the conditions for pre-freezing further include: the vacuum degree is 0 mbar.

[0056] In a specific example, the conditions for rewarming include: the temperature is 15 °C to 25 °C.

[0057] Understandably, in the present invention, the temperature for rewarming includes but is not limited to 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C. In a more specific example, the temperature for rewarming is 18°C to 22°C.

[0058] In a specific example, the conditions for rewarming further include: the time is 5 min to 15 min. Understandably, the time for rewarming includes but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min.

[0059] In a specific example, the conditions for rewarming further include: the vacuum degree is 0.4 mbar to 0.6 mbar. Understandably, in the present invention, the vacuum degree for rewarming includes but is not limited to 0.4 mbar, 0.45 mbar, 0.5 mbar, 0.55 mbar, 0.6 mbar. In a more specific example, the vacuum degree for rewarming is 0.45 mbar to 0.55 mbar.

[0060] Understandably, in the present invention, the temperatures for the first-stage drying and the second-stage drying both refer to the set temperatures, and the times both include the total duration of the heating process and the constant-temperature process after the end of the previous stage. More specifically, the duration of the heating process for the first-stage drying and the second-stage drying is 10 min to 20 min. The temperature for pre-freezing refers to the set temperature, and the time for pre-freezing includes the total duration of the cooling process starting from room temperature and the constant-temperature process. More specifically, the duration of the cooling process for pre-freezing is 10 min to 20 min. The temperature for rewarming refers to the set temperature, and the time for rewarming includes the duration of the cooling process after the end of the second-stage drying. More specifically, the duration of the cooling process for rewarming is 10 min to 20 min.

[0061] In a more specific example, the freeze-drying is carried out with variable temperature according to the following procedure:

[0062] 0 min to a, the temperature is cooled from room temperature to A; a is selected from any value within the range of 10 min to 20 min, and A is selected from any value within the range of -35°C to -25°C;

[0063] a to b, the temperature is kept constant at A; b is selected from any value within the range of 190 min to 200 min;

[0064] b to c, the temperature is heated from A to B; c is selected from any value within the range of 200 min to 220 min, and B is selected from any value within the range of -12°C to -10°C;

[0065] c to d, the temperature is kept constant at B; d is selected from any value within the range of 560 min to 580 min;

[0066] From d to e, the temperature is raised from B to C; e is selected from any value within the range of 570 min to 600 min, and C is selected from any value within the range of 32 °C to 38 °C;

[0067] From e to f, the temperature is kept constant at C; f is selected from any value within the range of 3750 min to 3780 min;

[0068] From f to g, the temperature is lowered from C to D; g is selected from any value within the range of 3760 min to 3800 min, and D is selected from any value within the range of 15 °C to 25 °C.

[0069] In a specific example, the emulsification conditions include: the rotation speed is 1200 rpm to 2500 rpm. It can be understood that in the present invention, the rotation speed of emulsification includes but is not limited to 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, 2100 rpm, 2200 rpm, 2300 rpm, 2400 rpm, 2500 rpm.

[0070] In a preferred example, the rotation speed of emulsification is 1200 rpm to 1800 rpm. The inventors of the present invention found that the best effect of bupivacaine microspheres is obtained when the rotation speed of emulsification is limited within the range of 1200 rpm to 1800 rpm. Specifically, on the premise of ensuring a relatively large particle size of the microspheres, it can meet the rapid release in the early stage of drug administration, and the drug release amount can reach more than 65% within 10 minutes. During the entire therapeutic effect time, it can release slowly and stably, and the drug release amount can reach more than 75% within 48 hours.

[0071] In a specific example, the emulsification conditions further include: the time is 1 min to 3 min. It can be understood that in the present invention, the emulsification time includes but is not limited to 1 min, 1.5 min, 2 min, 2.5 min, 3 min. In a more specific example, the emulsification time is 1.5 min to 2.5 min.

[0072] In a more specific example, the emulsification process includes rapidly injecting the oil phase into the aqueous phase at 4 °C to 8 °C and shearing and emulsifying at a rotation speed of 1200 rpm to 2500 rpm for 1 min to 3 min using a disperser.

[0073] In a specific example, in PLGA, the molar ratio of LA to GA is 50:50.

[0074] In a specific example, the organic solvent is dichloromethane.

[0075] In a specific example, the oil phase satisfies one or more of the following conditions:

[0076] (1) The mass ratio of bupivacaine base to PLGA is 1:1;

[0077] (2) In the oil phase, the total mass concentration of bupivacaine base and PLGA is (0.25 - 0.5) g / mL;

[0078] (3) The volume ratio of the oil phase to the water phase is 1:(140 - 160).

[0079] It can be understood that in the present invention, in the oil phase, the total mass concentration of bupivacaine base and PLGA includes but is not limited to 0.25 g / mL, 0.3 g / mL, 0.35 g / mL, 0.4 g / mL, 0.45 g / mL, 0.5 g / mL. The volume ratio of the oil phase to the water phase includes but is not limited to 1:140, 1:145, 1:148, 1:149, 1:150, 1:151, 1:152, 1:155, 1:160.

[0080] In a specific example, in the water phase, the mass concentration of polyvinyl alcohol is (0.005 - 0.01) g / mL. It can be understood that in the present invention, in the water phase, the mass concentration of polyvinyl alcohol includes but is not limited to 0.005 g / mL, 0.006 g / mL, 0.007 g / mL, 0.008 g / mL, 0.009 g / mL, 0.01 g / mL.

[0081] In a specific example, the curing conditions include: at a rotation speed of 140 rpm to 180 rpm, first stir at a temperature of 18°C to 22°C for 0.8 h to 1.2 h, and then stir at a temperature of 33°C to 37°C for 3.3 h to 3.7 h. More specifically, the curing conditions include: at a rotation speed of 150 rpm to 170 rpm, first stir at a temperature of 19°C to 21°C for 0.9 h to 1.1 h, and then stir at a temperature of 34°C to 36°C for 3.4 h to 3.6 h.

[0082] In a specific example, before washing after curing, there is also a concentration step. Specifically, the concentration is carried out by centrifugation. More specifically, the centrifugation conditions include cryogenic centrifugation at a rotation speed of 5000 rpm to 7000 rpm.

[0083] In a specific example, the detergent used for washing is water. More specifically, the water is purified water.

[0084] In a specific example, after freeze-drying the wet microspheres, a sieving step is further included. Specifically, sieving is carried out by means of screening with a sieve mesh. It can be understood that in the present invention, the particle size of the microspheres obtained after freeze-drying is relatively large, so the product can be collected by screening with an ordinary sieve mesh.

[0085] The present invention also provides bupivacaine microspheres prepared by the above preparation method. It can be understood that the above bupivacaine microspheres are bupivacaine microspheres for injection.

[0086] The following further describes the bupivacaine microspheres of the present invention and their preparation method in detail in conjunction with specific examples. The raw materials used in the following examples are all commercially available products unless otherwise specified.

[0087] PLGA: model DLG 2.5A, manufacturer is Evonik Specialty Chemicals (Shanghai) Co., Ltd., specification 100 g / bag;

[0088] Polyvinyl alcohol: model 17-88(06), manufacturer is Jiangxi Alpha High-Tech Pharmaceutical Co., Ltd.;

[0089] Bupivacaine base: manufacturer is Siegfried Evionnaz SA.

[0090] Example 1

[0091] This example provides a preparation method of bupivacaine microspheres, which is as follows:

[0092] S1. Mix bupivacaine base, PLGA and dichloromethane to prepare an oil phase; wherein, the molar ratio of LA to GA in PLGA is 50:50, the mass ratio of bupivacaine base to PLGA is 1:1, and the oil phase concentration is 50%;

[0093] S2. Mix polyvinyl alcohol and water to prepare an aqueous phase; wherein, the concentration of the polyvinyl alcohol solution is 1%;

[0094] S3. Rapidly inject the oil phase into the aqueous phase controlled at 4-8°C, and the volume ratio of the oil phase to the aqueous phase is 1:150; then use a disperser to shear and emulsify at a rotation speed of 1200 rpm for 2 min, stir and solidify at a rotation speed of 160 rpm at 20°C for 1 h, stir and solidify at 35°C for 3.5 h, remove dichloromethane to obtain solidified microspheres, centrifuge and concentrate at a rotation speed of 6000 rpm for 1 time and wash 4 times, and collect the wet microspheres;

[0095] S4. Carry out freeze-drying according to the freeze-drying program designed in Table 1, and then sieve and mix 2 times with a 0.178 mm sieve mesh to obtain bupivacaine microspheres.

[0096] Table 1

[0097]

[0098] Example 2

[0099] This example provides a method for preparing bupivacaine microspheres, which is as follows:

[0100] S1. Mix bupivacaine base, PLGA and dichloromethane to prepare an oil phase; wherein, the molar ratio of LA to GA in PLGA is 50:50, the mass ratio of bupivacaine base to PLGA is 1:1, and the concentration of the oil phase is 50%;

[0101] S2. Mix polyvinyl alcohol and water to prepare an aqueous phase; wherein, the concentration of the polyvinyl alcohol solution is 1%;

[0102] S3. Rapidly inject the oil phase into the aqueous phase controlled at 4 - 8°C, and the volume ratio of the oil phase to the aqueous phase is 1:150; then use a disperser to shear and emulsify at 1800 rpm for 2 min, stir and solidify at 160 rpm at 20°C for 1 h, stir and solidify at 35°C for 3.5 h, remove dichloromethane to obtain solidified microspheres, freeze - centrifuge and concentrate at 6000 rpm for 1 time and wash 4 times, and collect the wet microspheres;

[0103] S4. Perform freeze - drying according to the freeze - drying program designed in Table 1, and then sieve and mix 2 times using a 0.178 mm sieve to obtain bupivacaine microspheres.

[0104] Example 3

[0105] This example provides a method for preparing bupivacaine microspheres, which is as follows:

[0106] S1. Mix bupivacaine base, PLGA and dichloromethane to prepare an oil phase; wherein, the molar ratio of LA to GA in PLGA is 50:50, the mass ratio of bupivacaine base to PLGA is 1:1, and the concentration of the oil phase is 25%;

[0107] S2. Mix polyvinyl alcohol and water to prepare an aqueous phase; wherein, the concentration of the polyvinyl alcohol solution is 0.5%;

[0108] S3. Rapidly inject the oil phase into the aqueous phase controlled at 4 - 8°C, and the volume ratio of the oil phase to the aqueous phase is 1:150; then use a disperser to shear and emulsify at 2500 rpm for 2 min, stir and solidify at 160 rpm at 20°C for 1 h, stir and solidify at 35°C for 3.5 h, remove dichloromethane to obtain solidified microspheres, freeze - centrifuge and concentrate at 6000 rpm for 1 time and wash 4 times, and collect the wet microspheres;

[0109] S4. Perform freeze - drying according to the freeze - drying program designed in Table 1, and then sieve and mix 2 times using a 0.178 mm sieve to obtain bupivacaine microspheres.

[0110] Comparative Example 1

[0111] This comparative example provides a method for preparing bupivacaine microspheres, which is as follows:

[0112] S1. Mix bupivacaine base, PLGA and dichloromethane to prepare an oil phase; wherein, the molar ratio of LA to GA in PLGA is 50:50, the mass ratio of bupivacaine base to PLGA is 1:1, and the concentration of the oil phase is 50%;

[0113] S2. Mix polyvinyl alcohol and water to prepare an aqueous phase; wherein, the concentration of the polyvinyl alcohol solution is 1%;

[0114] S3. Rapidly inject the oil phase into the aqueous phase controlled at 4 - 8°C, and the volume ratio of the oil phase to the aqueous phase is 1:150; then use a disperser to shear and emulsify at a speed of 1200 rpm for 2 min, stir and solidify at a speed of 160 rpm at 20°C for 1 h, stir and solidify at 35°C for 3.5 h, remove dichloromethane to obtain solidified microspheres, freeze - centrifuge and concentrate once at a speed of 6000 rpm and wash 4 times, and collect the wet microspheres;

[0115] S4. Perform freeze - drying according to the freeze - drying program designed in Table 2, and then pass through a 0.178 - mm sieve and mix 2 times to obtain bupivacaine microspheres.

[0116] Table 2

[0117]

[0118] Comparative Example 2

[0119] This comparative example provides a method for preparing bupivacaine microspheres, which is as follows:

[0120] S1. Mix bupivacaine base, PLGA and dichloromethane to prepare an oil phase; wherein, the molar ratio of LA to GA in PLGA is 50:50, the mass ratio of bupivacaine base to PLGA is 1:1, and the concentration of the oil phase is 50%;

[0121] S2. Mix polyvinyl alcohol and water to prepare an aqueous phase; wherein, the concentration of the polyvinyl alcohol solution is 1%;

[0122] S3. Rapidly inject the oil phase into the aqueous phase controlled at 4 - 8°C, and the volume ratio of the oil phase to the aqueous phase is 1:150; then use a disperser to shear and emulsify at a speed of 1800 rpm for 2 min, stir and solidify at a speed of 160 rpm at 20°C for 1 h, stir and solidify at 35°C for 3.5 h, remove dichloromethane to obtain solidified microspheres, freeze - centrifuge and concentrate once at a speed of 6000 rpm and wash 4 times, and collect the wet microspheres;

[0123] S4. Perform freeze-drying according to the freeze-drying procedure designed in Table 2, and then sieve and mix twice using a 0.178 mm sieve to obtain bupivacaine microspheres.

[0124] Effect verification test

[0125] Perform effect verification experiments on the bupivacaine microspheres prepared in the above Examples 1 to 3 and Comparative Examples 1 to 2, including particle size distribution, drug loading, release curve, and microscopic observation.

[0126] The measurement data of Examples 1 to 3 are shown in Table 3. From the data, it can be seen that the microspheres have a large particle size and rapid release in the early stage. The release curve diagram is as Figure 1 shown. Observe the freeze-dried powder of the sieved microspheres with a scanning electron microscope. The scanning electron microscope image of the bupivacaine microspheres prepared in Example 1 is as Figure 2 shown. It can be seen that the surface of the freeze-dried powder of the microspheres is round. Use a thin blade head to cut the bupivacaine microspheres prepared in Example 1 at high speed and freeze them. The internal morphology of the microspheres observed by scanning electron microscope has pores, as Figure 3 shown.

[0127] The measurement data of Comparative Examples 1 to 2 are shown in Table 4. From the data, it can be seen that the microspheres have a large particle size, but the release is slower in the early stage. The release curve diagram is as Figure 4 shown. Figure 4 Among them, Control Example 1 refers to Comparative Example 1, and Control Example 2 refers to Comparative Example 2. Observe the freeze-dried powder of the sieved microspheres with a scanning electron microscope. The scanning electron microscope image of the bupivacaine microspheres prepared in Comparative Example 1 is as Figure 5 shown. It can be seen that the surface of the freeze-dried powder of the microspheres is not round. Use a thin blade head to cut the bupivacaine microspheres prepared in Comparative Example 1 at high speed and freeze them. The internal structure of the microspheres observed by scanning electron microscope is hollow and expanded, as Figure 6 shown.

[0128] Table 3

[0129]

[0130]

[0131] Table 4

[0132]

[0133] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0134] The above-described embodiments merely represent several implementation manners of the present invention, which are convenient for understanding the technical solutions of the present invention specifically and in detail, but should not be construed as limiting the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present invention are all within the protection scope of the appended claims of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the content of the appended claims, and the specification and drawings can be used to explain the content of the claims.

Claims

1. A preparation method of bupivacaine microspheres, characterized in that, It includes the following steps: Mix bupivacaine base, PLGA and an organic solvent to prepare an oil phase; Mix polyvinyl alcohol and water to prepare an aqueous phase; Mix the oil phase and the aqueous phase, emulsify, then solidify, and then wash to prepare wet beads; Freeze-dry the wet beads to prepare bupivacaine microspheres; Among them, the freeze-drying process sequentially goes through four stages: pre-freezing, primary drying, secondary drying and rewarming; the conditions for the primary drying include: the temperature is -12°C to -10°C, and the vacuum degree is 0.4 mbar to 0.6 mbar; the conditions for the secondary drying include: the temperature is 32°C to 38°C, and the vacuum degree is 0.4 mbar to 0.6 mbar.

2. The preparation method of bupivacaine microspheres according to claim 1, characterized in that, The conditions for the pre-freezing include: the temperature is -35°C to -25°C.

3. The preparation method of the bupivacaine microspheres according to claim 1, wherein, The conditions for the rewarming include: the temperature is 15°C to 25°C.

4. The preparation method of bupivacaine microspheres according to claim 1, wherein, The conditions for emulsification include: the rotation speed is 1200 rpm to 2500 rpm.

5. The preparation method of bupivacaine microspheres according to claim 1, characterized in that In the PLGA, the molar ratio of LA and GA is 50:

50.

6. The preparation method of bupivacaine microspheres according to claim 1, wherein, The organic solvent is dichloromethane.

7. The preparation method of bupivacaine microspheres according to claim 1, characterized in that, The oil phase satisfies one or more of the following conditions: (1) The mass ratio of bupivacaine base to PLGA is 1:1; (2) In the oil phase, the total mass concentration of bupivacaine base and PLGA is (0.25 - 0.5) g / mL; (3) The volume ratio of the oil phase to the aqueous phase is 1:(140 - 160).

8. The preparation method of bupivacaine microspheres according to claim 1, wherein, In the aqueous phase, the mass concentration of polyvinyl alcohol is (0.005 - 0.01) g / mL.

9. The preparation method of bupivacaine microspheres according to any one of claims 1 to 8, characterized in that, The conditions for solidification include: at a rotation speed of 140 rpm to 180 rpm, first stir at a temperature of 18°C to 22°C for 0.8 h to 1.2 h, and then stir at a temperature of 33°C to 37°C for 3.3 h to 3.7 h.

10. A bupivacaine microsphere prepared by the preparation method according to any one of claims 1 to 9.

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