Bupivacaine sustained-release gel injection and preparation method and application thereof

Abstract

The present application relates to a bupivacaine sustained-release gel injection and a preparation method and application thereof, the components of the bupivacaine sustained-release gel injection include bupivacaine, degradable polymer, alkaline adjuvant and biocompatible organic solvent.The bupivacaine sustained-release gel injection provided by the present application has higher drug loading and lower burst level, is convenient to administer, can prolong the release of the encapsulated bupivacaine to 5-7 days, has rapid onset, and can exert sustained analgesic effect in vivo.

Description

Technical Field

[0001] This invention relates to the field of biomedical technology, and in particular to a bupivacaine sustained-release gel injection solution, its preparation method, and its application. Background Technology

[0002] Postoperative pain is pain that occurs after surgery. It is a type of acute pain, mainly caused by the acute trauma (incision) caused by the surgery itself. The peak period is usually 24-48 hours after surgery, and the duration is usually no more than 7 days. However, if the pain is not effectively controlled in the early stage, it may develop into chronic postoperative pain, which seriously affects the patient's quality of life.

[0003] Bupivacaine is a commonly used amide-type local anesthetic in clinical practice. Due to its long duration of action, significant separation of sensory and motor blockade, and strong anesthetic efficacy, it is widely used in spinal anesthesia, epidural anesthesia, brachial plexus blocks, postoperative anesthesia and analgesia, and the treatment of some long-term, severe cancer pain. The first commercially available bupivacaine product was bupivacaine hydrochloride injection, developed and marketed by Hospira in 1972 under the brand name Marcaine. It was used for anesthesia and analgesia in surgical, oral, diagnostic, and obstetric procedures. Because of its short half-life, a single injection only maintains analgesia for about 5 hours. To meet analgesic needs, clinical practice typically employs methods such as catheter implantation, patient-controlled analgesia pumps, and nerve destruction to maintain the therapeutic effect. This not only causes unnecessary suffering and psychological harm to patients but also wastes medical resources and increases medical costs. Therefore, developing long-acting formulations of pivicaine can not only reduce the number of injections, lower treatment costs, and alleviate the economic burden on patients, but also reduce medical resource consumption and transportation costs, thus having significant social and economic benefits.

[0004] Developed by Pacira Pharmaceuticals in the United States, Bupivacaine liposome injection (trade name EXPAREL) was the first liposomal local anesthetic approved for clinical use. It is a honeycomb-structured multi-vesicle liposome produced using DepoFoam technology, and a single direct injection can produce analgesia for up to 72 hours. Exparal was first approved in 2011 for local infiltration anesthesia, and in 2018 it was further approved for brachial plexus block via interspinous groove recording. In multiple clinical trials, including those for breast augmentation, total knee replacement, and inguinal hernia repair, it has shown several advantages over bupivacaine hydrochloride injection. However, Exparal suffers from drawbacks such as easy vesicle rupture, limited embedding rate and drug loading, and poor stability. Durrect Pharmaceuticals in the United States developed bupivacaine gel solution (trade name Posimir). The core technology involves blending sucrose isobutyrate (SAIB), benzyl alcohol, and bupivacaine into a liquid, which, upon injection, forms a continuously releasing drug reservoir. Currently, it is only suitable for intra-articular administration, and clinical data show that its continuous release only lasts for 24 hours.

[0005] Therefore, it is necessary to develop an injectable, longer-acting sustained-release formulation and its preparation method to solve the above problems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a bupivacaine sustained-release gel injection, its preparation method, and its application. The bupivacaine sustained-release gel injection provided by this invention has a high drug loading capacity and a low burst release level, is convenient to administer, and can extend the release of encapsulated bupivacaine over 5-7 days, exhibiting rapid onset of action and providing sustained analgesia.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a bupivacaine sustained-release gel injection solution, wherein the components of the bupivacaine sustained-release gel injection solution include bupivacaine, a biodegradable polymer, an alkaline adjuvant, and a biocompatible organic solvent.

[0009] When using organic solvents as diluents for biodegradable polymers to prepare gel reservoirs, the problem of excessive burst release due to initial diffusion of the organic solvent is often encountered. This invention unexpectedly discovered that the addition of an alkaline additive can effectively control the burst release of bupivacaine. The reason for this is likely that the alkaline additive interacts with the acidic groups of the polymer, increasing viscosity and thus slowing down polymer degradation and delaying burst release.

[0010] In addition, the alkaline adjuvant dissolves in the body along with the drug, which can effectively improve the acidic environment caused by the degradation of biopolymers, thereby reducing the protonation of bupivacaine in the acidic environment. This, to a certain extent, avoids the obstacle that protonated bupivacaine cannot enter nerve cells after ionization, thus effectively prolonging the analgesic effect of bupivacaine.

[0011] Preferably, the bupivacaine sustained-release gel injection comprises, by weight, 1 part bupivacaine, 0.2-10 parts biodegradable polymer, 0.01-2 parts alkaline additive, and 0.5-300 parts biocompatible organic solvent.

[0012] Preferably, the bupivacaine sustained-release gel injection comprises, by weight, 1 part bupivacaine, 0.5-6 parts biodegradable polymer, 0.04-0.3 parts alkaline additive, and 1-20 parts biocompatible organic solvent.

[0013] In this invention, the biodegradable polymer can be, for example, 0.5 parts, 1 part, 2 parts, 4 parts, 6 parts, etc.; the alkaline additive can be, for example, 0.04 parts, 0.08 parts, 0.12 parts, 0.24 parts, 0.3 parts, etc.; and the biocompatible organic solvent can be, for example, 1 part, 5 parts, 10 parts, 15 parts, 20 parts, etc.

[0014] Preferably, the biodegradable polymer includes any one or a combination of at least two of polylactic acid-polyethylene glycol copolymer (PELA), lactide-glycolic acid copolymer (PLGA), or polylactide (PLA).

[0015] Preferably, the percentage content of polyethylene glycol in the polylactic acid-polyethylene glycol copolymer is 2-40% (e.g., 2%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.), and more preferably 5-30%.

[0016] Preferably, in the lactide-glycolic acid copolymer, the molar ratio of lactide to glycolide is 50:50-85:15 (e.g., 50:50, 60:40, 70:30, 80:20, 85:15, etc.), and more preferably 75:25-85:15.

[0017] Preferably, the molecular weight of the biodegradable polymer is 5-30 kDa (e.g., 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, etc.), and more preferably 10-25 kDa.

[0018] Preferably, the biocompatible organic solvent includes any one or a combination of at least two of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), acetone, 2-pyrrolidone, propylene carbonate, glyceryl triacetate, benzyl benzoate, or propylene glycol, with N-methylpyrrolidone being the most preferred.

[0019] Preferably, the alkaline additive includes any one or a combination of at least two of arginine, lysine, magnesium hydroxide, calcium hydroxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, sodium bicarbonate, or magnesium-aluminum mixture.

[0020] Preferably, the alkaline auxiliaries include any one or a combination of two of arginine (ARG) or lysine (LYS).

[0021] In a second aspect, the present invention provides a method for preparing the bupivacaine sustained-release gel injection according to the first aspect, the preparation method comprising the following steps:

[0022] (1) A slow-release solution is obtained by mixing a biodegradable polymer, a biocompatible organic solvent and an alkaline additive;

[0023] (2) Add bupivacaine to the sustained-release solution and stir to dissolve to obtain the bupivacaine sustained-release gel injection.

[0024] Thirdly, the present invention provides the use of the bupivacaine sustained-release gel injection solution according to the first aspect in the preparation of analgesic or local anesthetic products.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The present invention uses biodegradable polymer as sustained-release material and alkaline additives to effectively control the burst release of drug in bupivacaine sustained-release gel injection, prolong the duration of action, reduce the number of administrations and toxic side effects, and has a fast onset of action in vivo with excellent analgesic effect.

[0027] (2) The preparation method provided by the present invention is simple, has no drug loss during the preparation process, and has a high drug loading capacity, which is conducive to scale-up production. Attached Figure Description

[0028] Figure 1 The liquid used in Example 1 is the bupivacaine sustained-release gel injection liquid.

[0029] Figure 2 The bupivacaine sustained-release gel injection solution from Example 1 was injected into a pH 7.4 phosphate buffer solution to form an in situ gel.

[0030] Figure 3 The rheological curve of bupivacaine at 25°C is shown in Example 1.

[0031] Figure 4 This is a time-effect diagram of the bupivacaine sustained-release gel injection administered to guinea pigs in Example 1.

[0032] Figure 5 The curves showing the cumulative pain score-time changes in rats treated with bupivacaine sustained-release gel injection in Examples 1, 2, and 3 are shown.

[0033] Figure 6 The graph shows the mechanical pain threshold values ​​of rats using bupivacaine gel injection in Examples 1, 2, and 3. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0035] Examples 1-10, Comparative Examples 1-2

[0036] Examples 1-10 and Comparative Example 1 each provide a bupivacaine sustained-release gel injection, and Comparative Example 2 provides bupivacaine sustained-release microspheres, the components of which are shown below:

[0037]

[0038]

[0039] The only difference between Example 4 and Example 3 is that the molecular weight of the polymer PLA is 29 kDa.

[0040] The only difference between Example 5 and Example 3 is that the polymer is PLGA50:50 with a molecular weight of 11 kDa.

[0041] The only difference between Example 6 and Example 1 is that the amount of organic solvent NMP is reduced to 1.2g;

[0042] The only difference between Example 7 and Example 2 is that the organic solvent is 7g DMSO;

[0043] The only difference between Example 8 and Example 2 is that the organic solvent is 6g of NMP and 2g of DMSO;

[0044] The only difference between Example 9 and Example 2 is that the organic solvent is 2g of NMP and 6g of DMSO;

[0045] The only difference between Example 10 and Example 3 is that the amount of organic solvent NMP is increased to 100g;

[0046] The only difference between Comparative Example 1 and Example 1 is that no alkaline additive is added.

[0047] The preparation methods of the bupivacaine sustained-release gel injection provided in Examples 1-10 and Comparative Example 1 include the following steps:

[0048] (1) A slow-release solution is obtained by mixing a biodegradable polymer, a biocompatible organic solvent and an alkaline additive;

[0049] (2) Add bupivacaine to the sustained-release solution in small amounts several times under stirring conditions, and stir to dissolve to obtain the bupivacaine sustained-release gel injection.

[0050] The preparation method of bupivacaine sustained-release microspheres provided in Comparative Example 2 is an oil-in-water emulsion method, which includes the following steps: dissolving bupivacaine and a biodegradable polymer in an organic solvent to obtain an oil phase, using a 0.5 wt% polyvinyl alcohol solution as the external aqueous phase, homogenizing and emulsifying, and further solidifying the formed oil-in-water emulsion into microspheres by stirring at 600 rpm, repeatedly washing the solidified microspheres with pure water to remove residual polyvinyl alcohol, and then freeze-drying to obtain bupivacaine microspheres.

[0051] Test Example 1

[0052] Appearance, viscosity, and in vitro release tests

[0053] Test method: The viscosity of bupivacaine sustained-release gel injection was tested using a cone-plate rheometer. The gel was then injected into an in vitro pH 7.4 phosphate buffer solution to test the in vitro release efficiency.

[0054] like Figure 1 As shown, the bupivacaine sustained-release gel injection prepared in Example 1 is a pale yellow transparent liquid with good fluidity.

[0055] like Figure 2 As shown, the bupivacaine sustained-release gel injection solution prepared in Example 1 was injected into pH 7.4 phosphate buffer to form a gel-like semi-solid.

[0056] like Figure 3 As shown, the shear stress of the bupivacaine sustained-release gel injection prepared in Example 1 is proportional to the shear rate, and the viscosity is independent of the shear rate, which is close to that of a Newtonian fluid.

[0057] Viscosity and in vitro release tests were performed on the products provided in Examples 1-10 and Comparative Examples 1-2, and the results are shown in Table 1.

[0058] Table 1

[0059]

[0060] Test results show that the bupivacaine sustained-release gel injection in Examples 1-3, when injected into in vitro pH 7.4 phosphate buffer, can achieve slow release of the drug within 7 days, effectively prolonging the duration of drug action.

[0061] In Example 4, the polymer molecular weight was too high, resulting in slow drug release, with a cumulative release of only 71% over 7 days. In Example 5, PLGA50:50 with a polymer of 11 kDa was used, and the cumulative release of the resulting injection solution exceeded 80% in 1 day, indicating an excessively fast release rate. In Example 6, the amount of organic solvent was too low, and the active pharmaceutical ingredient could not be completely dissolved, resulting in a particulate dispersion. After heating and stirring, the particles gradually dissolved, causing needle blockage during the release test. Therefore, it was determined that this drug combination was not suitable for the preparation of bupivacaine gel injection. In Examples 7-9, DMSO or a mixture of NMP and DMSO was used as the solvent, and the cumulative release over 7 days was 71-80%, indicating a slow release rate. In Example 10, the amount of organic solvent was too high, resulting in an overall rapid in vitro release, which failed to achieve the sustained-release effect.

[0062] In Comparative Example 1, no alkaline additive was added. The resulting injectable liquid showed rapid release in 4-7 days during in vitro testing, with a cumulative release of 87% in 4 days, which failed to achieve a sustained-release effect. The microspheres provided in Comparative Example 2 showed relatively slow overall in vitro release, which could not meet the requirement of sufficient release in 7 days.

[0063] Test Example 2

[0064] Anesthesia effect test

[0065] Test samples: Bupivacaine gel injection prepared in Example 1 and commercially available bupivacaine hydrochloride injection.

[0066] Test method: The local anesthetic effect of the sample on guinea pigs was tested using the needle prick method.

[0067] Male adult guinea pigs, weighing 350-450g, were purchased from Guangdong Vital River Laboratory Animal Technology Co., Ltd. The animals were housed in the animal facility of the Experimental Animal Center of Hunan University of Traditional Chinese Medicine. After a 5-day acclimatization period and veterinary inspection, the fur was shaved (or removed) along the midline of the guinea pig's back, covering an area of ​​at least 6cm x 6cm. After 12 hours of continued rearing, the animals were placed on a rodent board, and the shaved area was pricked with a needle eight times. Animals showing a negative reaction (no contraction or squealing in the skin area on the guinea pig's back after needle prick) were discarded. Only qualified guinea pigs were selected for unified rearing.

[0068] Ten qualified guinea pigs were randomly divided into two groups of five each. The grouping and dosage were as follows: control group (bupivacaine hydrochloride injection, 10 mg / kg), and Example 1 group (10 mg / kg). During the experiment, the skin at the drug administration site was stimulated with a needle. A contraction response or a squealing sound from the stimulated skin area was considered a positive reaction; otherwise, it was considered a negative reaction. The average number of negative reactions at a single time point in each group was calculated to obtain the average number of negative reactions at that time point for each group. The average painless response rate (effect) was then calculated from the average number of negative reactions.

[0069] Test Results: Effect-Time of Bupivacaine Extended-Release Gel Injection in Guinea Pigs after Administration Figure 4 As shown, the control group had almost no analgesic effect 6 hours after administration, while the average painless response rate remained above 50% 7 days after administration in Example 1, indicating that the bupivacaine gel injection provided by the present invention has a long duration of efficacy.

[0070] Test Example 3

[0071] Analgesic effect test

[0072] Test samples: Bupivacaine gel injection from Examples 1-3, and commercially available bupivacaine hydrochloride injection. Test methods:

[0073] SD rats (SPF grade), adult males weighing 250–300g and aged 8–10 weeks, were purchased from Beijing Huafukang Biotechnology Co., Ltd. After 4 days of acclimatization, the rats were weighed and randomly divided into a paw incision group and a non-paw incision group based on their weight. The paw incision group was further divided into 5 subgroups based on weight, with 6 rats in each subgroup. The non-paw incision group was tested for thermal pain threshold and divided into 5 subgroups based on both weight and thermal pain threshold, with 6 rats in each subgroup.

[0074] The rats were fasted for 12 hours prior to administration. At the time of administration, the rats were anesthetized with isoflurane, and 30,000 units of potassium penicillin were injected into the triceps surae muscle of the lower leg. The rats were fixed in a prone position on a rat restraint frame, covered with a pore-sealed drape, and the right hind limb was exposed and its fur shaved. The area was disinfected three times with iodine and alcohol. A longitudinal incision of approximately 6-8 mm was made in the midline of the right posterior thigh to expose the subcutaneous muscle. After blunt dissection of the biceps femoris, semitendinosus, and semimembranosus muscles with hemostatic forceps, the white, thick sciatic nerve was visible. One-third of the needle was inserted into the muscle approximately 1.5 mm lateral to the sciatic nerve, and 0.5 mL of the drug was injected. The muscle was then cleaned and the wound sutured.

[0075] No model was established in the non-plantar incision group of rats. The model was established in the plantar incision group of rats as follows: After the sciatic nerve injection, the rat's right foot was taken about 0.5 cm away from the heel as the starting point, and an incision was made in the middle of the sole of the foot towards the toe. The longitudinal incision was about 1 cm long. The plantar muscle of the foot was lifted with forceps and longitudinally cut 0.8-1 cm. The incision was completely cut and separated to both sides, keeping the origin, insertion and attachment of the muscle intact. After hemostasis, the incision was closed with 5-0 sutures using interrupted mattress suture method.

[0076] The analgesic efficacy and duration of the test samples were evaluated using cumulative pain scores, mechanical pain tests, and thermal pain tests.

[0077] 1) Cumulative pain score detection method: Rats were placed on a metal mesh, with each rat in a separate small compartment, and allowed to adapt for 2 minutes; then observed for 3 minutes. The most frequently used posture within 1 minute was used as the standard, and a total of 3 minutes of observation were conducted. Data were recorded 3 times and added together to obtain the cumulative pain score. The scoring standard was based on the Brennan method.

[0078] 2) Mechanical pain detection method: The rats were placed on a metal mesh, and each rat was placed in a small compartment. After acclimatization for 2 minutes and the animals were in a quiet and awake state, the skin within 2 mm of the toe tip of the incision on the right hind paw was stimulated with an electronic pain meter. Each stimulation was performed at 5-10 second intervals, and a total of 3 tests were conducted and the values ​​were recorded. The mean value was taken as the mechanical pain threshold.

[0079] 3) Thermal pain test method: Turn on the hot plate apparatus and set the initial temperature to 52±0.5℃. Once the temperature is reached, the experiment can begin. Remove the organic cover from the hot plate, place the rat on the hot plate, close the organic cover, and click the test button. After the rat licks its right paw for the first time, lock the time and record it. Take the average of the three thresholds as the thermal pain threshold of the rat. If the rat does not react within 60 seconds, its paw should be immediately removed from the hot plate to avoid burns, and the threshold should be calculated based on 60 seconds.

[0080] The groups and dosages are as follows: blank group (solvent group, NMP+PELA, drug-free gel), positive control group (bupivacaine hydrochloride injection, 2.5 mg / animal), Example 1 group (10 mg / animal), Example 2 group (10 mg / animal), and Example 3 group (10 mg / animal).

[0081] Test results:

[0082] The cumulative pain test results of the blank group, positive control group, and groups 1-3 of Examples are shown in Table 2. For example, the cumulative pain score-time change curves of rats receiving bupivacaine sustained-release gel injection in groups 1-3 of Examples are shown in Table 2. Figure 5 As shown.

[0083] Table 2

[0084]

[0085]

[0086] The results showed that the cumulative pain score of the control group rats decreased over time. The positive control group rats had significantly lower scores than the control group (solvent group) at 0.5 h after drug administration, and showed an increasing trend. After 2 h, the scores decreased, and at 24 h, 48 h, 72 h, 96 h, 120 h, and 168 h, the scores were similar to the control group (solvent group). The rats in Examples 1, 2, and 3 had significantly lower scores than the control group at 0.5 h after drug administration, and showed a decreasing trend, remaining lower than the control group even at 168 h. The cumulative pain scores of Examples 1 and 2 were similar, while the cumulative pain score of Example 3 was slightly higher than that of Examples 1 and 2.

[0087] The mechanical pain test results of the blank group (solvent group), positive control group, and groups in Examples 1-3 are shown in Table 3. For example, the mechanical pain threshold values ​​of bupivacaine gel injection in rats in Examples 1, 2, and 3 are shown in the following graph. Figure 6 As shown.

[0088] Table 3

[0089]

[0090] The results showed that the mechanical pain threshold of rats in the positive control group was significantly higher than that in the blank group from 0.5 to 2 hours, and the mechanical pain threshold was close to that in the blank group from 24 to 168 hours. The mechanical pain threshold of rats in the Example 1, Example 2 and Example 3 groups from 0.5 to 168 hours after administration was higher than that in the positive control group and the blank group.

[0091] The results of thermal pain perception tests for the blank group, positive control group, and groups in Examples 1-3 are shown in Table 4.

[0092] Table 4

[0093]

[0094] The results showed that the thermal pain threshold of rats in the blank injection group did not change much over time, indicating that no sensory blockade occurred in this group of rats; the duration of sensory blockade in rats in the positive control group was about 2 hours, not exceeding 24 hours. Rats in the Example 1 and Example 2 groups showed long-lasting sensory blockade compared with the blank group and the positive control group. Rats in the Example 3 group showed sensory blockade from 0.5 to 120 hours after administration compared with the blank group and the positive control group, and the value at 168 hours was close to that of the blank group.

[0095] The overall results show that the bupivacaine gel injection prepared in this invention has significant sustained-release and long-lasting analgesic effects.

Claims

1. A bupivacaine sustained-release gel injection, characterized in that, The bupivacaine sustained-release gel injection comprises, by weight, 1 part bupivacaine, 0.5-6 parts biodegradable polymer, 0.04-0.3 parts alkaline additive, and 10-20 parts biocompatible organic solvent. The biodegradable polymer is any one or a combination of at least two of polylactic acid-polyethylene glycol copolymer or polylactide; The molecular weight of the biodegradable polymer is 10-25 kDa; The alkaline auxiliary is any one or a combination of at least two of arginine or lysine; The biocompatible organic solvent is N-methylpyrrolidone.

2. The bupivacaine sustained-release gel injection solution according to claim 1, characterized in that, In the polylactic acid-polyethylene glycol copolymer, the percentage content of polyethylene glycol is 2-40%.

3. The bupivacaine sustained-release gel injection solution according to claim 2, characterized in that, In the polylactic acid-polyethylene glycol copolymer, the percentage content of polyethylene glycol is 5-30%.

4. A method for preparing a bupivacaine sustained-release gel injection solution according to any one of claims 1-3, the preparation method comprising the following steps: (1) A slow-release solution is obtained by mixing a biodegradable polymer, a biocompatible organic solvent, and an alkaline additive; (2) Add bupivacaine to the sustained-release solution and stir to dissolve, thereby obtaining the bupivacaine sustained-release gel injection solution.

5. The use of a bupivacaine sustained-release gel injection solution according to any one of claims 1-3 in the preparation of analgesic or local anesthetic products.

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