A long-acting preparation of amide local anesthetic based on prodrug technology

Abstract

The present invention provides a long-acting preparation of an amide local anesthetic based on prodrug technology, and relates to the field of pharmaceutical chemistry and pharmaceutical preparation technology. The prodrug of the amide local anesthetic has poor water solubility, strong fat solubility, and is easily soluble in oil to form an oil-based injection, which can form a drug reservoir locally after injection, prolonging the half-life of the amide local anesthetic in the body, prolonging the effective analgesic time, and reducing the injection frequency. The oil-based injection of the prodrug of the amide local anesthetic achieves the sustained release of the amide local anesthetic through two rate-limiting steps: the prodrug of the amide local anesthetic with strong fat solubility needs to be slowly dissolved from the oil matrix, and the dissolved prodrug of the amide local anesthetic is hydrolyzed under the action of the hydrolase in the body to release the amide local anesthetic, thereby exerting analgesic efficacy. The drug production method provided by the present invention is simple and easy to operate, convenient to produce, and highly practical.

Description

Technical Field

[0001] The invention relates to the field of pharmaceutical chemistry and pharmaceutical preparation technology, and in particular to a long-acting preparation of amide local anesthetics based on prodrug technology. Background Art

[0002] Pain is an unpleasant feeling produced when the body is stimulated by external harmful stimuli. It is often mixed with other sensations and accompanied by strong emotional reactions. It is a complex subjective feeling. Clinically, pain is usually accompanied by symptoms such as tissue damage, hyperalgesia and inflammation. Patients not only suffer great mental torture, but also cause the body's immune system to malfunction and induce complications, and even in severe cases, endanger the patient's life. Anesthesia refers to the phenomenon that external pain stimulation cannot induce physiological pain response under normal or pathological conditions of the body. Anesthetics are a class of drugs that can reversibly and temporarily make the body lose consciousness or pain. In clinical practice, timely and reasonable use of anesthetics can effectively relieve and treat pain and protect the body. Local anesthetics, also known as local anesthetics, are drugs that reversibly block the occurrence and conduction of sensory nerve impulses through local administration. After using local anesthetics, the patient remains conscious and the pain of the local tissue injected disappears. Generally speaking, the effect of local anesthetics is limited to the site of administration and is mainly used for pain caused by surgery or inflammation.

[0003] Amide local anesthetics are based on ester local anesthetics, with amide bonds replacing ester bonds, and the positions of amine and carbonyl groups are interchanged, so that the nitrogen atom is connected to the aromatic ring, and the carbonyl group is part of the side chain, which constitutes the basic structure of amide local anesthetics. Since lidocaine was successfully used in clinical practice, a variety of drugs have been used clinically and have become an important part of injectable local anesthetics. Representative drugs include lidocaine, mepivacaine, bupivacaine, ropivacaine, prilocaine, etc. Lidocaine and mepivacaine have poor penetration properties and are generally used for infiltration anesthesia, nerve block and epidural anesthesia. A single administration of local anesthetics generally maintains analgesia for about 0.5h to 8h. For example, the onset time of procaine is 2 to 5min, and analgesia can be maintained for about 0.5h to 1h. Compared with these short-acting local anesthetics, bupivacaine and ropivacaine can be used as long-acting local anesthetics. Bupivacaine takes effect 5 to 10 minutes after use, has a strong effect, and lasts for a relatively long time, up to 3 to 6 hours, with a half-life of 2.7 hours. Ropivacaine also has a long duration of action, with a local infiltration analgesia lasting 2 to 6 hours, and a nerve block anesthesia lasting about 3.7 to 8.7 hours, with a strong effect on sensory block. Both drugs have been widely used in surgical regional blocks, epidural anesthesia, and epidural postoperative or labor analgesia.

[0004] Although bupivacaine and ropivacaine are long-acting local anesthetics among amide local anesthetics, the duration of their anesthetic effect still cannot meet clinical needs. This is because the pain peaks 24 to 48 hours after surgery, and postoperative pain generally lasts for 3 to 7 days. A single dose of conventional local anesthetics cannot effectively relieve postoperative pain and requires multiple injections within a day or a few days. Patient compliance is low. Therefore, new long-acting local anesthetics have been developed one after another. People use various physical, biological, and chemical methods to improve local anesthetic injections and continue to explore drug delivery systems such as nanoparticles, liposomes, in situ gels, and microspheres. Currently, the long-acting local anesthetics available for injection include bupivacaine multivesicular liposomes. Bupivacaine in situ gel wait.

[0005] Bupivacaine multivesicular liposome suspension injection was developed by Pacira Pharmaceuticals, Inc. in the United States. It is clinically used for surgical site infiltration to treat postoperative pain, and can also be used for interscalene brachial plexus block. The drug uses a new type of liposome prepared by reservoir foam technology, which can exert a nerve block effect for 72 hours after a single injection in clinical practice. However, multivesicular liposomes have poor stability and the drug is prone to leakage during storage. Therefore, the temperature needs to be controlled at 2°C to 8°C for transportation and storage, and the shelf life is only 30 days at room temperature. This product also has the problem of complex production, requiring differentiated centrifugation equipment, and there are many key quality attribute control points in the process, and the product yield is low. In addition, the use of "Class II reagents" such as dichloromethane in the process, coupled with the need for sterile production and guarantee processes, makes the matching degree of most workshops not meet the requirements.

[0006] Bupivacaine in situ gel was developed by DURECT in the United States. It can be used for direct drug delivery to the subacromial space under arthroscopy and can also provide postoperative analgesia for subacromial decompression under arthroscopy. The drug uses a biodegradable polymer, sucrose acetate isobutyrate (SAIB), which is a flowing solution before injection and forms a gel after injection at the sutured wound site, delaying the release of bupivacaine and achieving a 72-hour analgesic effect. This type of in situ gel, as a packaging system for toxic local anesthetics, is greatly affected by the environment and has a high risk of drug leakage. In addition, the excipients used in the preparation are also currently not within the scope of approval by regulatory authorities.

[0007] There are still some basic studies that have made useful explorations on the long-acting release of amide local anesthetics. For example, Christopher B. Weldon et al., in the article "Electrospun drug-eluting sutures for localanesthesia (J Control Release. 2012 Aug 10; 161 (3): 903-9.)", used electrospinning technology to load bupivacaine into surgical sutures, attempting to use it in postoperative wound sutures to achieve a slow release and sustained analgesic effect. This product can achieve an analgesic effect of 3-7 days in mice, but since organic solvents are introduced during the preparation process, the complete removal of organic solvents is a certain challenge for textile materials. In the article "Thermoresponsive nanogels for prolonged duration local anesthesia (ActaBiomater.2012 Oct;8(10):3596-605.)", Todd Hoare et al. selected poly N-isopropylacrylamide (NIPAM) and other materials to prepare bupivacaine thermosensitive hydrogel, which can provide sustained analgesia for 8 hours in rats without obvious toxic side effects, but NIPAM is not a compliant excipient approved by drug administration departments of various countries. In the article "Local sustained delivery of bupivacaine HCl from a new castor oil-based nanoemulsion system (Drug Deliv Transl Res.2018 Jun;8(3):515-524.)", Heni Rachmawati et al. prepared a castor oil nanoemulsion loaded with bupivacaine, proving that it has a certain sustained release effect after subcutaneous injection, but the long-term stability of the injection emulsion has always been a major challenge for this type of preparation. Since microspheres have good sustained-release effects, some professionals have also investigated the sustained-release effects of this type of preparation on cocaine-like drugs. For example, Francesca Tarballi et al., in the article “Potential avoidance of adverse analgesic effects using a biologically "smart" hydrogel capable of controlled bupivacaine release (J Pharm Sci. 2014 Nov; 103(11): 3724-3732.)”, used thermosensitive materials such as Pluronic F127, PLGA and chitosan to prepare bupivacaine microsphere complexes, which can be released continuously in vitro for 6-8 days.

[0008] To date, there are no literature reports or patent authorizations for amide local anesthetics using precursor drug technology to prolong the duration of local analgesia in the body. Summary of the invention

[0009] The purpose of the present invention is to solve the technical problem of lack of precursor drugs for amide local anesthetics in the prior art.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] The present application provides an amide local anesthetic comprising a compound of the following chemical formula:

[0012]

[0013] Preferably, in the chemical formula, R 1 =C n H 2n+1 , n=1-10; R 2 =XC n H 2n+1 or XC n H 2n-1 ,n=1-18X= / ,O,orNH;R 3 =H.

[0014] Preferably, the compound is selected from one or more combinations of the following compounds:

[0015] I 1: (1-butyl-N-(2,6-dimethylphenyl)piperidin-2-carboxamido)tridecanoic acid methyl ester, I 2: (N-(2,6-dimethylphenyl)-1-propylpiperidin-2-carboxamido) palmitic acid methyl ester,

[0016] I 3: (N-(2,6-dimethylphenyl)-1-propylpiperidin-2-carboxamide) methyl stearate,

[0017] I 4: (N-(2,6-dimethylphenyl)-1-methylpiperidin-2-carboxamido) 2,2-dimethylundec-10-enoic acid methyl ester,

[0018] I 5: 2-(2-methoxyethoxy)ethoxyacetic acid methyl ester,

[0019] I 6: (N-(2,6-dimethylphenyl)-1-propylpiperidin-2-carboxamido)methyldecyl carbonate,

[0020] I 7:1-(N-(2,6-dimethylphenyl)-1-propylpiperidin-2-carboxamido)dodecanoic acid ethyl ester,

[0021] I 8: Methyl (1-butyl-N-(2,6-dimethylphenyl)piperidine-2-carboxamido)-2-(2-methoxyethoxy)acetate.

[0022] The present invention also provides a method for preparing an amide prodrug, and the drug synthesis route is as follows:

[0023]

[0024] Preferably, the method comprises the following steps:

[0025] S1: Take formaldehyde or aliphatic aldehyde, dissolve it and anhydrous zinc chloride in acetonitrile, protect with N2, and place in an ice bath;

[0026] S2: Then slowly add the corresponding acyl chloride dropwise, and after the addition is complete, continue the reaction. After the reaction is complete, filter the solid and wash the filter cake with dichloromethane, and concentrate the filtrate under reduced pressure to obtain an intermediate;

[0027] S3: Dissolve the N-(2,6-xylyl)piperidine-2-carboxamide derivative in tetrahydrofuran, add sodium hydride and stir at room temperature;

[0028] S4: then add dropwise to the intermediate and heat;

[0029] S5: After the reaction is completed, cool to room temperature and pour the reaction solution into water, extract with ethyl acetate, dry the organic layer with anhydrous sodium sulfate, concentrate under reduced pressure, and purify by column chromatography to obtain the prodrug.

[0030] Preferably, the amide anesthetic is an oil-based injection, and the preparation method of the oil-based injection is: taking oil, heating and sterilizing, cooling, filtering, and obtaining a sterilized oil matrix; taking the compounds respectively, adding a certain amount of sterilized injection oil, stirring until completely dissolved, packaging, filling with nitrogen, filling, sterilizing, and storing at room temperature.

[0031] Preferably, the amide anesthetic is an injectable microcapsule, and the preparation method of the injectable microcapsule is as follows: take the compound, add a certain amount of sterile injection oil, stir until completely dissolved, add an appropriate amount of gum arabic and water thereto, grind to prepare colostrum, then add a certain concentration of gelatin aqueous solution, stir while keeping warm, move to a water bath to keep warm and stir continuously, cool, add a certain concentration of formaldehyde solution and sodium hydroxide solution, continue stirring, filter, dry, use water for injection, disperse with high-speed stirring, add mannitol, freeze-dry, and store at room temperature.

[0032] The present application also provides a preparation of a local anesthetic prodrug, characterized in that: the specific preparation of the amide anesthetic can slowly release the amide local anesthetic at the injection site after being injected into the body.

[0033] Furthermore, the present application also provides a preparation of a local anesthetic prodrug, characterized in that the amide anesthetic can achieve a long-acting local analgesic effect of not less than 5 days after being injected into the body.

[0034] Preferably, the present application also provides a preparation of a local anesthetic prodrug, characterized in that the amide anesthetic can be used to suppress postoperative pain after being injected into the body.

[0035] Compared with the prior art, this application has the following beneficial effects:

[0036] 1. The local long-acting anesthetic drugs that have been marketed in the prior art use special preparation production methods or special pharmaceutical excipients. For example, the It is a kind of storage foam technology The new liposomes prepared use a patented reservoir foam technology in the production process, which is complex to operate and difficult to control. In addition, expensive pharmaceutical excipients 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG) and 1,2-dierucoylphosphatidylcholine (DEPC) are used, resulting in high preparation costs. For example, the drug Bupivacaine Meloxicam Sustained Release Injection (trade name: ), by Heron Therapeutics, a US company, using a Polyorthoesters, which are sustained-release materials manufactured using this technology, are also complex in technology, difficult to scale up for production, difficult to control quality, and have high preparation costs, which creates patent barriers to the imitation of this preparation.

[0037] The drug production method provided by the present invention is to first use a chemical synthesis method to structurally transform the amide local anesthetic, and the chemical substances used in the synthesis process are all common substances in organic chemistry, cheap and easy to obtain; the synthesis conditions are not harsh. Because the synthesis belongs to prodrug synthesis, the synthesis route is short and the production is convenient. In addition, the chemical synthesis process of small molecule drugs is highly controllable and the product purity is high, which is conducive to the quality control of raw materials. From the perspective of preparation production, the amide local anesthetic prodrug preparation provided by the present invention is to dissolve the prodrug of the amide local anesthetic in an oil-based injection, or to encapsulate it using a microcapsule preparation. The excipients used in the production of these preparations are cheap and easy to obtain, the production cost is low, and the production process is mature. Therefore, from the controllability and simplicity of raw material and preparation production, the drug production method provided in this application is low in cost, and can greatly reduce the burden on patients after clinical use.

[0038] 2. The scheme of synthesizing fat-soluble prodrugs of amide drugs and slowly releasing them in the body to exert long-term analgesia, before the application of the present invention, no similar invention or utility model has been published in domestic or foreign publications, used in China, or known to the public in other ways, and no similar invention or utility model has been applied for by others to the patent administration department and recorded in the patent application documents published after the application date. Similarly, there has been no preparation of prodrugs of amide local anesthetics into oil injections or injectable microcapsules. Therefore, the present invention has obvious novelty.

[0039] 3. In the prior art, long-term analgesia is generally achieved through the following ways: (1) Continuously infusing analgesic drug solution into the vein through an analgesic pump to produce systemic analgesia; (2) Preparing analgesics or analgesic drug precursors into a certain preparation (such as intravenous emulsion) and administering it systemically to produce systemic analgesia; (3) Preparing analgesics into a certain preparation (such as the marketed and ), local administration, produces local analgesia. For the first method, it mainly relies on an analgesic pump, which is inconvenient to use because the analgesic pump needs to infuse the drug solution through an intravenous needle. For the second method, systemic administration may cause some side effects. For the third method, local administration is used for local analgesia, which is convenient and has few side effects; however, the analgesic effect of this preparation can generally only last for 3 days, and the analgesic effect after 3 days is significantly lower than that on the first and second days.

[0040] The technology provided by the present invention can not only maintain the advantages of local analgesia and convenient administration of local administration, but also extend the analgesic duration to no less than 5 days, which is much longer than the analgesic duration of the currently available local long-acting analgesic preparations, and therefore has obvious creativity and obvious progressive characteristics. The mechanism of producing long-acting analgesia is also innovative: the prodrug of the amide local anesthetic of the present invention has poor water solubility, strong fat solubility, and is easily soluble in oil to form an oil-based injection, which can form a drug reservoir locally after injection, prolonging the half-life of the amide local anesthetic in the body, prolonging the effective analgesic time, and reducing the injection frequency; the oil-based injection of the prodrug of the amide local anesthetic achieves the sustained release of the amide local anesthetic through two rate-limiting steps: in the first step, the prodrug of the amide local anesthetic with strong fat solubility needs to be slowly dissolved from the oil matrix, and in the second step, the dissolved prodrug of the amide local anesthetic is hydrolyzed under the action of the hydrolase in the body to release the amide local anesthetic, thereby exerting a long-acting analgesic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The synthetic route of the amide prodrug in one embodiment of the present invention is as follows;

[0042] Figure 2 The plasma drug (ropivacaine)-time curve after intramuscular injection of ropivacaine hydrochloride solution, ropivacaine free base oil solution and I3 oil solution in rats according to one embodiment of the present invention (n=6);

[0043] Figure 3 This is a line graph showing the change in PWT over time of postoperative rats after injection of physiological saline, ropivacaine hydrochloride injection, bupivacaine multivesicular liposome injection, I3 oil solution, and I3 injection microcapsule around the sciatic nerve of the right ankle joint in one embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with specific embodiments.

[0045] The present application provides a method for preparing an amide prodrug, comprising the following steps:

[0046] See also Figure 1 The synthetic route shown is to dissolve formaldehyde or aliphatic aldehyde and anhydrous zinc chloride in acetonitrile, protect with N2, and ice bath. The solid is filtered and the filter cake is washed with dichloromethane, and the filtrate is concentrated under reduced pressure to obtain an intermediate. The N-(2,6-xylyl)piperidine-2-carboxamide derivative is dissolved in tetrahydrofuran, and sodium hydride is added and stirred at room temperature. Then it is added dropwise to the intermediate and heated. After the reaction is completed, it is cooled to room temperature and the reaction solution is poured into water, extracted with ethyl acetate, and the organic layer is dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography to obtain the prodrug.

[0047] The present application also provides a method for preparing an oil-based injection, wherein the oil-based injection comprises a precursor drug of an amide local anesthetic and an injection oil, wherein the content of the precursor drug of the amide local anesthetic is 1-40 mg / mL. The injection oil comprises soybean oil for injection, sesame oil for injection, tea oil for injection, corn oil for injection, peanut oil for injection, cottonseed oil for injection, olive oil for injection, castor oil for injection, medium-chain fatty acids (C6-C 24 )wait.

[0048] The preparation method of the oil-based injection is as follows:

[0049] Take the injection oil, heat and sterilize it at 150℃ for 1h, let it cool, filter it, and obtain the sterilized oil base.

[0050] A certain amount of the precursor drug of the amide local anesthetic is taken respectively, dissolved in the sterile oil under stirring, filled and sterilized.

[0051] The present application also provides a method for preparing an injectable microcapsule, wherein the injectable microcapsule comprises a precursor drug of an amide local anesthetic and a capsule material. In one embodiment, the capsule material comprises gelatin or gum arabic.

[0052] The preparation method of the injectable microcapsule is as follows: a certain amount of the prodrug of the amide local anesthetic is taken, dissolved in the sterilized oil under stirring, an appropriate amount of gum arabic and water is added thereto, and colostrum is prepared by grinding, and then a certain concentration of gelatin aqueous solution is added, and the mixture is stirred under heat preservation, and the mixture is moved to a water bath pot for heat preservation and continuous stirring, and the mixture is cooled, and a certain concentration of formaldehyde solution and sodium hydroxide solution are added, and the mixture is continuously stirred, and the mixture is filtered, dried, dispersed with injection water, and stirred at high speed, and mannitol is added, and the mixture is freeze-dried and stored at room temperature.

[0053] The present application also provides the use of an amide compound or a pharmaceutically acceptable salt thereof in the preparation of a local anesthetic, wherein the local anesthetic is in the form of a preparation that slowly releases the amide compound or a pharmaceutically acceptable salt thereof in vivo within a preselected time period.

[0054] The present application is described below in conjunction with specific embodiments:

[0055] Embodiment 1:

[0056] according to Figure 1 According to the synthetic route shown, formaldehyde or aliphatic aldehyde (0.06 mol) and anhydrous zinc chloride (0.163 g, 0.0012 mol) were dissolved in acetonitrile, protected by N2, and placed in an ice bath.

[0057] Then, the acid chloride was slowly added dropwise. After the addition was completed, the mixture was reacted at 25°C for 1 hour, and then heated to 90°C and reacted for 16 hours.

[0058] After the reaction was completed, the solid was filtered and the filter cake was washed with DCM. The filtrate was concentrated under reduced pressure to obtain compound 5 in a yield of 84%.

[0059] N-(2,6-Dimethylphenyl)piperidine-2-carboxamide derivative (0.1 mol) was dissolved in THF, and NaH (38 g, 0.95 mol) was added and stirred at room temperature for 15 min.

[0060] Then compound 5 (0.3 mol) was added dropwise and heated to 90°C for 2 h. After the reaction was completed, the mixture was cooled to room temperature and poured into water, extracted with EA, and the organic layer was dried over anhydrous Na2SO4, concentrated under reduced pressure, and purified by column chromatography to obtain an off-white solid I with a yield of 70%.

[0061] The obtained compound I is shown below:

[0062] Table 1 Codes of preferred compounds of formula I and their corresponding structures

[0063]

[0064] Compound I1: 1 H NMR (400MHz, CDCl3) δ7.20-7.16(m,1H,ArH),7.10-7.07(m,2H,ArH),6.20-6.13(m,2H,CH2),5.85-5.75(m,1H ,CH),5.00-4.93(m,2H,CH2),3.61-3.53(m,1H,CH),2.95-2.87(m,1H,CH),2.72-2.64(m,2H,CH2),2.63-2.56( m,1H,CH),2.40-2.34(m,2H,CH2),2.25(s,6H,CH3),2.07-1.99(m,2H,CH2),1.97-1.88(m,1H,CH2),1.79-1.6 8(m,1H,CH2),1.67-1.53(m,6H,CH2),1.52-1.41(m,2H,CH2),1.39-1.19(m,16H,CH2),0.95-0.89(m,3H,CH3).

[0065] Compound I2: 11H NMR (400 MHz, CDCl3) δ 7.22 - 7.14 (m, 1H, ArH), 7.12 - 7.06 (m, 2H, ArH), 6.21 - 6.10 (m, 2H, CH2), 3.63 - 3.51 (m, 1H, CH), 2.93 - 2.86 (m, 1H, CH2), 2.76 - 2.63 (m, 2H, CH2), 2.62 - 2.56 (m, 1H, CH2), 2.40 - 2.32 (m, 2H, CH2), 2.25 (s, 6H, CH3), 1.98 - 1.88 (m, 1H, CH2), 1.79 - 1.69 (m, 1H, CH2), 1.68 - 1.46 (m, 8H, CH2), 1.33 - 1.27 (m, 6H, CH2), 1.23 - 1.26 (m, 18H, CH2), 0.95 - 0.86 (m, 6H, CH3).

[0066] Compound I3: 1H NMR (400 MHz, CDCl3) δ 7.21 - 7.15 (m, 1H, ArH), 7.11 - 7.06 (m, 2H, ArH), 6.21 - 6.10 (m, 2H, CH2), 3.63 - 3.48 (m, 1H, CH), 2.94 - 2.84 (m, 1H, CH2), 2.75 - 2.63 (m, 2H, CH2), 2.63 - 2.55 (m, 1H, CH2), 2.40 - 2.33 (m, 2H, CH2), 2.25 (s, 6H, CH3), 2.00 - 1.85 (m, 1H, CH2), 1.79 - 1.68 (m, 1H, CH2), 1.67 - 1.46 (m, 8H, CH2), 1.41 - 1.10 (m, 28H, CH2), 0.97 - 0.84 (m, 6H, CH3).

[0067] Compound I4: 11H NMR (400 MHz, CDCl3) δ 7.20 - 7.15 (m, 1H, ArH), 7.11 - 7.06 (m, 2H, ArH), 6.23 - 6.11 (m, 2H, CH2), 5.88 - 5.71 (m, 1H, CH), 5.14 - 5.04 (m, 1H, CH), 5.02 - 4.91 (m, 1H, CH), 3.69 - 3.47 (m, 1H, CH), 2.95 - 2.76 (m, 1H, CH2), 2.73 - 2.56 (m, 1H, CH2), 2.37 (s, 3H, CH3), 2.25 (s, 6H, CH3), 2.07 - 1.90 (m, 3H, CH2), 1.77 - 1.56 (m, 7H, CH2), 1.44 - 1.36 (m, 2H, CH2), 1.33 - 1.24 (m, 8H, CH2), 1.18 (s, 6H, CH3).

[0068] Compound I5: 1 1H NMR (400 MHz, CDCl3) δ 7.20 - 7.15 (m, 1H, ArH), 7.11 - 7.03 (m, 2H, ArH), 6.31 - 6.15 (m, 2H, CH2), 4.07 (s, 2H, CH2), 3.84 - 3.76 (m, 2H, CH2), 3.71 - 3.61 (m, 4H, CH2), 3.60 - 3.54 (m, 3H, 1CH, 2CH2), 3.38 (s, 3H, CH3), 2.99 - 2.83 (m, 1H, CH2), 2.77 - 2.47 (m, 3H, CH2), 2.25 (s, 6H, CH3), 2.01 - 1.86 (m, 1H, CH2), 1.83 - 1.68 (m, 1H, CH2), 1.67 - 1.40 (m, 6H, CH2), 1.03 - 0.83 (m, 3H, CH3).

[0069] Compound I6: 11H NMR (400 MHz, CDCl3) δ 7.22 - 7.14 (m, 1H, ArH), 7.11 - 7.05 (m, 2H, ArH), 6.29 - 6.20 (m, 2H, CH2), 4.24 - 4.13 (m, 2H, CH2), 3.63 - 3.51 (m, 1H, CH), 2.96 - 2.83 (m, 1H, CH2), 2.76 - 2.54 (m, 3H, CH2), 2.25 (s, 6H, CH3), 2.01 - 1.87 (m, 1H, CH2), 1.81 - 1.67 (m, 3H, CH2), 1.68 - 1.45 (m, 6H, CH2), 1.44 - 1.34 (m, 2H, CH2), 1.34 - 1.17 (m, 12H, CH2), 1.02 - 0.85 (m, 6H, CH3).

[0070] Compound I7: 1 1H NMR (400 MHz, CDCl3) δ 7.21 - 7.11 (m, 3H, ArH), 6.99 - 6.93 (m, 1H, CH), 3.60 - 3.49 (m, 1H, CH), 2.94 - 2.81 (m, 1H, CH2), 2.74 - 2.55 (m, 3H, CH2), 2.40 - 2.29 (m, 2H, CH2), 2.23 (s, 6H, CH3), 2.00 - 1.87 (m, 1H, CH2), 1.79 - 1.48 (m, 12H, 9CH2, 1CH3), 1.34 - 1.20 (m, 16H, CH2), 0.99 - 0.81 (m, 6H, CH3).

[0071] Compound I8: 1 1H NMR (400 MHz, CDCl3) δ 7.21 - 7.13 (m, 1H, ArH), 7.12 - 7.03 (m, 2H, ArH), 6.25 - 6.13 (m, 2H, CH2), 4.07 (s, 2H, CH2), 3.82 - 3.68 (m, 2H, CH2), 3.63 - 3.54 (m, 1H, CH), 3.53 - 3.41 (m, 2H, CH2), 3.38 (s, 3H, CH3), 3.00 - 2.84 (m, 1H, CH2), 2.75 - 2.62 (m, 2H, CH2), 2.62 - 2.47 (m, 1H, CH2), 2.25 (s, 6H, CH3), 2.00 - 1.85 (m, 1H, CH2), 1.80 - 1.69 (m, 1H, CH2), 1.68 - 1.51 (m, 4H, CH2), 1.51 - 1.29 (m, 4H, CH2), 0.98 - 0.84 (m, 3H, CH3).

[0072] Example 2: Preparation of amide local anesthetic prodrug long-acting injection (oil-based injection)

[0073] Accurately weigh appropriate amounts of I1-I8 amide local anesthetic prodrugs, add 30 mL of sterilized soybean oil, and stir until completely dissolved to obtain a soybean oil solution of amide local anesthetic prodrugs (based on ropivacaine, the concentration is 7.5 mg / mL). The prepared preparations are dispensed into sterile glass bottles, filled with nitrogen, sealed, sterilized at 121°C for 15 min, and stored at room temperature.

[0074] Example 3: Preparation of amide prodrug long-acting injection (injection microcapsule)

[0075] The amide prodrug long-acting injection (injection microcapsule) is prepared according to the following steps:

[0076] (1) Accurately weigh 2.00 g of gelatin, add 100 mL of water, stir and dissolve in a 50°C water bath to prepare a gelatin solution, and keep it warm at the same temperature for later use;

[0077] (2) Accurately weigh 1.00 g of the oil-based preparation prepared in Example 2, place it in a mortar, add 0.5 g of gum arabic and grind for 2 min, then add 2 mL of water and continue to grind rapidly in the same direction to prepare colostrum; then add 1.50 g of gum arabic and continue to grind until uniform, transfer to a beaker, rinse the mortar with water 3 times to transfer all the colostrum to the beaker, add water to 100 mL, stir, add the gelatin water solution prepared in step (1), and stir continuously at a constant temperature (50° C.) at a speed of 300 r / min;

[0078] (3) Add glacial acetic acid solution dropwise to adjust the pH to 4.0. Continue stirring at 300 r / min for 15 min;

[0079] (4) The above solution was rapidly cooled to about 10°C in an ice bath, and 1 mL of 37% formaldehyde solution was added while stirring at 300 r / min, and the pH value was adjusted to about pH 8.5 with 20% NaOH aqueous solution, and the stirring was continued for 30 min, and the mixture was allowed to stand and spray dried;

[0080] (5) The powder obtained by the above spray drying is dispersed in a mannitol solution (5%, w / v), and freeze-dried to obtain an amide prodrug long-acting injection (injection microcapsule), which is stored at room temperature.

[0081] The compounds obtained in this application are verified by combining the verification experiments as follows:

[0082] Validation experiment 1 In vitro dissolution study

[0083] The apparatus and research conditions used in the in vitro release experiment are described as follows: a magnetic stirrer is placed in a beaker, and then 150 mL of release medium is added, the release medium is 0.01M PBS (pH 7.4) containing 0.05% SDS, 1 mL of the soybean oil solution of I1-I8 in Example 2 (in terms of ropivacaine, the concentration is 7.5 mg / mL) is added to a transparent glass tube, and the beaker mouth and the upper end of the glass tube are sealed with a sealing film, leaving a sampling hole. The beaker is placed on a magnetic stirrer and stirred continuously at 100 r / min at room temperature 25°C. At the time point of 72h, 1 mL of release medium is taken out, the sample is diluted with methanol, and the concentration of I1-I8 is determined using HPLC-UV, and the release degree at 72h is calculated. Each group of experiments is carried out in parallel 3 times.

[0084] Control study: A 7.5 mg / mL soybean oil solution of ropivacaine free base was used for in vitro dissolution study in the same manner. At 0, 24, 48, and 72 h, 1 mL of release medium was taken out and 1 mL of the same release medium solution was added in time. The sample was diluted with methanol, and the ropivacaine concentration was determined by HPLC-UV, and the cumulative release was calculated. Each group of experiments was carried out in parallel for 3 times.

[0085] The results are shown in Table 2: The dissolution rate of ropivacaine free base from the oil matrix reached 91.36% in 72 hours. Compared with ropivacaine free base, the dissolution rate of I1-I8 amide local anesthetic prodrugs from the soybean oil matrix was much lower than that of ropivacaine free base due to their higher lipophilicity. The dissolution rate in 72 hours was between 69.56% and 84.22%, among which I3 was the slowest to dissolve from the oil matrix. This shows that the soybean oil solution of I1-I8 has good sustained release performance.

[0086] Table 2 Dissolution of I1-I8 amide local anesthetic prodrugs from their oil solutions (72h)

[0087]

[0088] Validation Test 2: In vitro Dissolution Study

[0089] A magnetic stirrer was placed in a beaker, and 150 mL of release medium was added. The release medium was 0.01 M PBS (pH 7.4) containing 0.05% SDS. An appropriate amount of the I1-I8 amide prodrug long-acting injection (injection microcapsule) prepared in Example 3 (in terms of ropivacaine, mass 7.5 mg) was taken and dispersed in the release medium. The beaker was placed on a magnetic stirrer and stirred continuously at 100 r / min at room temperature of 25°C. At the time point of 72 h, 1 mL of release medium was taken out, the sample was diluted with methanol, and the concentration of I1-I8 was determined using HPLC-UV. The release degree at 72 h was calculated, and 3 copies were carried out in parallel for each group of experiments.

[0090] The results are shown in Table 3. The dissolution of amide local anesthetic prodrugs I1-I8 from their respective injection microcapsules was slower, with the dissolution amounts at 72 hours ranging from 33.63% to 43.70%, among which I3 was the slowest to dissolve from the injection microcapsules.

[0091] Table 3 Dissolution of I1-I8 amide local anesthetic prodrugs from their injection microcapsules (72h)

[0092] Compound <![CDATA[I1]]> <![CDATA[I2]]> <![CDATA[I3]]> <![CDATA[I4]]> <![CDATA[I5]]> <![CDATA[I6]]> <![CDATA[I7]]> <![CDATA[I8]]> Dissolution (%) 36.76 36.30 33.63 38.59 41.92 37.06 38.23 43.70

[0093] Validation experiment 3: Pharmacokinetic properties of amide prodrug long-acting injection

[0094] 1. Solution preparation

[0095] Ropivacaine hydrochloride solution: Accurately weigh 26.9 mg of ropivacaine hydrochloride monohydrate and dissolve it in 3 mL of normal saline until it is fully dissolved to obtain a ropivacaine hydrochloride solution with a concentration of 8.98 mg / mL (based on ROP, the concentration is 7.5 mg / mL).

[0096] Ropivacaine free base oil solution: Accurately weigh 22.5 mg of ropivacaine free base, dissolve it in 3 mL of sterilized soybean oil, and ultrasonically vibrate until it is completely dissolved to obtain a ropivacaine free base soybean oil solution with a concentration of 7.5 mg / mL (based on ropivacaine, the concentration is 7.5 mg / mL).

[0097] The I3 oil solution obtained in Example 2 contained 15.6 mg / mL of I3 (i.e., ropivacaine prodrug) (calculated as ropivacaine, the concentration was 7.5 mg / mL).

[0098] 2. Quantitative conditions

[0099] Chromatographic conditions: chromatographic column: ACQUITYUPLC BEH C18 (100 mm × 2.1 mm, 1.7 μm); mobile phase: 0.1% formic acid solution (phase A, 5%)-acetonitrile (phase B, 95%); flow rate: 0.2 mL / min; column temperature: 40 ° C; injection volume: 5 μL. Mass spectrometry conditions: using electrospray ionization source (ESI+), scanning in multiple reaction monitoring (MRM) mode, positive ion detection; cone voltage: 40 V; collision energy: 28 eV. The ion pairs used for quantitative analysis were m / z 275.2→126.2 (ropivacaine), m / z 571.3→126.2 (I3), m / z 235→86 (lidocaine, internal standard).

[0100] 3. Experimental Methods

[0101] 12h before the experiment, SD rats were fasted but not allowed to drink water. According to ropivacaine, ropivacaine hydrochloride solution, ropivacaine free base oil solution and I3 oil solution (n=6) were injected into the right hind thigh lateral muscle at a dose of 7.5mg / kg. 0.3mL of blood was collected from the orbit at 0.25, 0.5, 1, 2, 3, 4, 6, 8, 12, 24, 36, 48, 60, and 72h after administration. The blood samples were all stored in EP tubes rinsed with physiological saline containing 0.1% sodium heparin, and then immediately centrifuged at 10,000r / min for 10min, the supernatant was separated, and stored in a -20℃ refrigerator for further analysis. The plasma samples were taken out of the -20℃ refrigerator and thawed, and vortexed for 30s to mix them evenly. Take 100 μL of plasma sample, add 50 μL of internal standard solution and vortex for 30 seconds to mix evenly, add 250 μL of acetonitrile and vortex for 1.5 minutes, centrifuge at 12,000 r / min for 10 minutes at 4°C, and take 200 μL of supernatant into the inner tube. All samples were processed and numbered and placed in a -80°C refrigerator until the measurement. DAS software 2.0 was used to perform pharmacokinetic analysis on the ropivacaine concentration and time data of each group.

[0102] 4. Experimental Results

[0103] The plasma drug (ropivacaine)-time curves after intramuscular injection of ropivacaine hydrochloride solution, ropivacaine free base oil solution and I3 oil solution in rats are shown in Figure 3 As shown. Figure 2 It can be seen that the plasma ropivacaine concentration in the ropivacaine hydrochloride solution group increased rapidly within 1 hour after administration, and then showed a rapid decline; similarly, the plasma ROP concentration in the ropivacaine oil solution group increased rapidly within 1 hour after administration, and then showed a rapid decline; the peak plasma ropivacaine concentration in the ropivacaine free base oil solution group was significantly lower than that in the ropivacaine hydrochloride solution group.

[0104] The above results show that after ropivacaine hydrochloride solution is injected into muscle tissue, ropivacaine can be quickly absorbed into the blood. However, due to the release of ropivacaine free base from soybean oil, the amount of ropivacaine released and absorbed by muscle tissue capillaries within 1 hour in the ropivacaine free base oil solution group is much lower than that in the ropivacaine hydrochloride solution group, so its ropivacaine peak concentration is lower. Compared with the two, the plasma ropivacaine concentration in the I3 oil solution group rises slowly, and its plasma ROP concentration before 1 hour is either lower than LOQ or very low. Before and for a long period of time after the ropivacaine concentration reaches its peak between 20h and 30h, the plasma ropivacaine level is at a low level and relatively stable, indicating that ropivacaine enters the blood slowly. The reason is that I3 needs to be slowly released from the oil base first (as the first rate-limiting step), and then ropivacaine is degraded from the I3 prodrug by the action of hydrolases (as the second rate-limiting step) before it can be absorbed by muscle tissue capillaries. From the slow release of I3, it can be inferred that the release rate of I3 from the oil base in vivo is also slow in theory; in addition, the hydrolysis of the prodrug structure of I3 under the action of plasma hydrolases and liver hydrolases is also a slow process. Therefore, the two rate-limiting steps of ropivacaine release from the I3 oil solution group play an important role in sustained release.

[0105] Table 4 Pharmacokinetic parameters of rat intramuscular administration for 72 h

[0106]

[0107] The pharmacokinetic data of the above preparations are shown in Table 4. The results show that after intramuscular injection of I3 oil solution, max 28.00±12.40h, T 1 / 2 17.80±8.38h, C max The AUC was 26.58±6.94μg / L and 1145.28±125.28μg / L·h. Compared with ropivacaine hydrochloride solution, T max It was extended by about 27 hours, which was 26 hours longer than the free base oil solution of ropivacaine.

[0108] Validation experiment 4: Analgesic properties of amide prodrug long-acting injections

[0109] 1. Experimental Animals

[0110] Healthy male Sprague-Dawley rats (SD rats, body weight 220 g ± 20 g) were provided by the Animal Experiment Center of Nantong University.

[0111] 2. Experimental Methods

[0112] 2.1 Experimental preparation

[0113] Ropivacaine hydrochloride injection (purchased from Hengrui Pharmaceuticals; specification: 100 mg / 10 mL), bupivacaine multivesicular liposome injection (prepared according to the method published in CN113797168A; specification: 266 mg / 20 mL), the I3 oil solution prepared in Example 3, and the I3 injection microcapsule prepared in Example 4.

[0114] 2.2 Establishment of postoperative pain model in rats

[0115] Before the experiment, SD rats were adaptively raised for one week, with the room temperature maintained at about 24°C, humidity at 55-70%, and 12h alternating light and dark lighting, during which the animals were free to eat and drink. The rats were randomly divided into 5 groups, 6 in each group, namely, normal saline group, ropivacaine hydrochloride injection group, bupivacaine multivesicular liposome injection group, I3 oil solution group, and I3 injection microcapsule group.

[0116] SD rats were anesthetized by inhalation of 2% isoflurane. The sole of the right hind paw was disinfected with alcohol, and the pain model was prepared under sterile conditions. A 1.0 cm longitudinal incision was made at about 0.5 cm from the sole of the foot with a No. 23 scalpel. After the skin was cut, the muscle was picked out and cut longitudinally. After light pressure to stop bleeding, the skin was sutured with 5-0 sutures, and the incision site was disinfected with iodine. Half an hour after the operation, the following preparations were injected near the sciatic nerve of the right ankle joint of the four groups of rats: (1) normal saline; (2) ropivacaine hydrochloride injection (injection dose: 1.5 mg based on ropivacaine); (3) bupivacaine multivesicular liposome injection (injection dose: 1.5 mg based on bupivacaine); (4) I3 oil solution (injection dose: 1.5 mg based on ropivacaine); (5) I3 injection microcapsule (injection dose: 1.5 mg based on ropivacaine).

[0117] 2.3 Von Frey pain assessment

[0118] Before administration (counted as 0h) and 1, 24, 48, 72, 96 and 120h after administration. The analgesic effect of the given preparation was evaluated by measuring the paw withdrawal threshold (PWT) of rats after mechanical stimulation after surgery by the Von Frey single fiber method. Two days before the experiment, the rats need to adapt to the test environment and mechanical stimulation every day to reduce errors. On the day of the experiment, the postoperative rats were placed in a customized separate transparent compartment with a metal mesh plate to adapt to the environment for half an hour, and the rats were allowed to calm down. Von Frey fibers with different pressure intensities were used to stimulate the area around the plantar incision of the right hind limb of the rat from small to large, and the fibers were bent for 3 to 4s. The rats were observed for paw withdrawal reactions, which were repeated three times. The lowest force of the rats' paw withdrawal reaction was the PWT value, and the data were recorded.

[0119] 3. Experimental results

[0120] The results of the Von Frey pain assessment are as follows: Figure 3 The analgesic effect of the ropivacaine hydrochloride injection group was obvious at 1 hour, but there was no significant difference between the performance at 24 hours and at other time points thereafter and the normal saline group, showing no analgesic effect.

[0121] The analgesic effect of the bupivacaine multivesicular liposome injection group was slightly weaker than that of the ropivacaine hydrochloride injection group at 1 hour, but it showed significant analgesic effects at 24, 48, and 72 hours, but the analgesic effect was significantly weakened from 96 hours onwards. This shows that the effective analgesia of bupivacaine multivesicular liposome injection can be maintained for 3 days, and the analgesic effect weakens after 3 days.

[0122] The analgesic effect of the I3 oil solution group at 1 hour was also slightly weaker than that of the ropivacaine hydrochloride injection group, but it showed significant analgesic effects at 24, 48, 72, 96 and 120 hours, indicating that the effective analgesia of the I3 oil solution can be maintained for 5 days.

[0123] The analgesic effect of the I3 injection microcapsule group was significantly weaker than that of the ropivacaine hydrochloride injection group at 1 hour, and was also weaker than that of the bupivacaine multivesicular liposome injection group and the I3 oil solution group at 24 hours, but it showed significant analgesic effects at 48, 72, 96 and 120 hours. This shows that the analgesic effect of the I3 injection microcapsule was not ideal 24 hours after administration due to the slow release of the drug at the beginning, but starting from 48 hours, its analgesic effect can be maintained for at least 120 hours.

[0124] The long-acting preparation of amide local anesthetics based on prodrug technology provided in the present application, and the drug production method provided in the present application are simple and easy to operate, convenient to produce, and highly practical; secondly, the prodrug of the amide local anesthetic of the present invention has poor water solubility, strong fat solubility, and is easily soluble in oil to prepare an oil-based injection, which can form a drug reservoir locally after injection, thereby prolonging the half-life of the amide local anesthetic in the body, prolonging the effective analgesic time, and reducing the injection frequency; the oil-based injection of the prodrug of the amide local anesthetic achieves the sustained release of the amide local anesthetic through two rate-limiting steps: in the first step, the prodrug of the highly fat-soluble amide local anesthetic needs to be slowly dissolved from the oil matrix, and in the second step, the dissolved prodrug of the amide local anesthetic is hydrolyzed under the action of the hydrolase in the body to release the amide local anesthetic, thereby exerting the analgesic effect.

Claims

1. An amide prodrug, characterized in that: The amide prodrug is selected from the following compounds of the chemical formula:

2. The method for preparing an amide prodrug according to claim 1, characterized in that: The drug synthesis route is as follows:

3. The method for preparing an amide prodrug according to claim 2, characterized in that: The following steps are involved: S1: Take compound 2, dissolve it and anhydrous zinc chloride in acetonitrile, protect with N2, and place in an ice bath; S2: Then slowly add compound 4 dropwise, and after the addition is complete, continue the reaction. After the reaction is complete, filter the solid and wash the filter cake with dichloromethane, and concentrate the filtrate under reduced pressure to obtain the intermediate compound 5; S3: Dissolve compound 1 in tetrahydrofuran, add sodium hydride and stir at room temperature; S4: then adding the intermediate compound 5 dropwise and heating; S5: After the reaction is completed, cool to room temperature and pour the reaction solution into water, extract with ethyl acetate, dry the organic layer with anhydrous sodium sulfate, concentrate under reduced pressure, and purify by column chromatography to obtain the prodrug I.

4. An amide local anesthetic, characterized in that: The amide anesthetic is an oil-based injection, and the preparation method of the oil-based injection is: taking oil, heating and sterilizing, cooling, filtering, and obtaining a sterilized oil matrix; taking the amide prodrug described in claim 1, adding a certain amount of sterilized injection oil, stirring until completely dissolved, packaging, filling with nitrogen, filling, sterilizing, and storing at room temperature.

5. An amide local anesthetic, characterized in that: The amide anesthetic is an injectable microcapsule, and the preparation method of the injectable microcapsule is as follows: take the amide prodrug described in claim 1, add a certain amount of sterile injection oil, stir until completely dissolved, add appropriate amounts of gum arabic and water thereto, grind to prepare colostrum, then add a certain concentration of gelatin aqueous solution, stir while keeping warm, move to a water bath to keep warm and stir continuously, cool, add a certain concentration of formaldehyde solution and sodium hydroxide solution, continue stirring, filter, dry, use water for injection, disperse with high-speed stirring, add mannitol, freeze-dry, and store at room temperature.

6. Use of the amide local anesthetic according to claim 4 or 5 in the preparation of drugs for inhibiting postoperative pain and providing long-acting local analgesia.

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