Patent Application
20190314281
The present invention relates to the technical field of medicine, and particularly to a local anesthetic analgesic sustained-release drug delivery system, and a preparation method and application thereof.
Clinical local anesthetic drugs mainly include esters and amides, the action duration of these drugs is less than 3 hours in general, and continuous administration is needed to maintain the appropriate plasma concentration in order to achieve the purpose of long-time analgesia. If such drugs are prepared into preparations with sustained-release functions such as microspheres, multivesicular liposomes and the like, the analgesic effect may be kept for a long time, and meanwhile, the tolerance of patients may be increased. Chinese patent with the patent no. CN102274183 B proposes two preparation methods of multivesicular liposomes. The first method includes: dissolving active pharmaceutical ingredient and osmotic pressure regulator in water to prepare an internal aqueous phase, adding a lipid phase prepared by dissolving lipid in an organic solvent to prepare W/O primary emulsion, adding an external aqueous phase containing osmotic pressure regulator to the upper layer of the W/O primary emulsion to prepare W/O/W multiple emulsion, and then removing the organic solvent from the multiple emulsion. In the method, coemulsifiers, which are frequently-used surfactants mainly for dextran, polyvinyl pyrrolidone and other tablets, are added in the preparation process, and the pH regulator is an acid frequently used in this technical field. The second method is different from the above-mentioned method in that: in the drug loading process thereof, a drug is dissolved in the external aqueous phase, to load the drug through the difference between the internal osmotic pressure and the external osmotic pressure of the multivesicular liposome rather than add the drug when preparing W/O. The method is similar to the pH gradient drug loading method or ion gradient drug loading method for ordinary liposomes. Because the multivesicular liposome is of a structure that most small vesicles are in a big vesicle, when drug is loaded using the technology, it is certainly that drug is preferentially loaded in the small vesicles of the outer layer. After drug is loaded in the small vesicles of the outer layer, the osmotic pressure of the small vesicles in the big vesicle after loading drug may be reduced. Thus, it is certainly that some small vesicles in the big vesicle of the multivesicular liposome are not filled with active drug. In addition, the multivesicular liposome is different from the ordinary liposome in that the multivesicular liposome contains triglyceride and other oil ingredients existing in the skeleton structure of each vesicle. In the patent, drug is dissolved in the external aqueous phase, so that the water-based drug must be disturbed by triglyceride in the process of entering the internal aqueous phase from the external aqueous phase and then the drug cannot enter inside the multivesicular liposome successfully. Moreover, the active pharmaceutical ingredients of the patent mainly include exenatide, topotecan and other drug which are unstable under the alkaline condition.
On this basis, the present invention provides a preparation of a multivesicular liposome containing an amide-type local anesthetic analgesic, thereby preparing a multivesicular liposome product with the advantages of high encapsulation percentage and good stability.
The technical problem to be solved by the present invention is to provide a preferable multivesicular liposome and a preparation method thereof, thereby preparing a multivesicular liposome product having the advantages of high encapsulation percentage and good stability and meeting various requirements.
To achieve the above purpose, the present invention adopts the following technical solution:
A novel local anesthetic analgesic sustained-release drug delivery system, including an internal aqueous phase, an external aqueous phase, an oil phase, an organic solvent, an isoosmotic regulator and a pH regulator, wherein the internal aqueous phase includes an analgesic, a drug solvent and a drug solubilizer; the external aqueous phase is removed finally, and the isoosmotic regulator and the pH regulator are added finally to obtain the sustained-release drug delivery system of the present invention.
The analgesic is selected from one of bupivacaine, levobupivacaine, ropivacaine, lidocaine and mepivacaine.
The drug solvent is selected from inorganic acid containing N or P, preferably, nitric acid and phosphoric acid.
The drug solubilizer is selected from saccharide or ring-shaped organic acid, preferably, ring-shaped organic acid; the saccharide is selected from monosaccharide or binary saccharide such as cane sugar, dextrose, fructose and the like, and the ring-shaped organic acid is selected from vitamin C, nicotinic acid, gallic acid or glucuronic acid.
The external aqueous phase is selected from one or more of saccharide, ring-shaped organic acid, organic base and deflocculant; the organic base is selected from lysine or arginine; and the deflocculant is selected from citrate, tartrate or phosphate.
The oil phase includes synthetic phospholipid, synthetic phosphatidylglycerol, cholesterol and glyceride. The synthetic phospholipid is selected from one or more of dierucoyl phosphatidylcholine (DEPC), dioleoyl phosphatidylcholine (DOPC), dipalmitoyl phosphatidylcholine (DPPC), distearoyl phosphatidylcholine (DSPC) and dimyristoyl phosphatidylcholine (DMPC); the synthetic phosphatidylglycerol is selected from one or more of dipalmitoyl phosphatidylglycerole (DPPG), dioleoyl phosphatidylglycerole (DOPG), dimyristoyl phosphatidylglycerole (DMPG) and distearoyl phosphatidylglycerole (DSPG); and the glyceride is selected from glycerol trioleate or tricaprylin.
The organic solvent is selected from trichloromethane, ethyl ether, n-hexane or other organic solvent immiscible with water, preferably, trichloromethane or ethyl ether.
The isoosmotic regulator is selected from 0.9% sodium chloride injection, 5% mannitol injection, sodium lactate ringer's injection or 5% glucose injection; and the isoosmotic regulator is used to regulate the osmotic pressure of the liposome suspension to make same reach an isotonic state. The sodium lactate ringer's injection is a mixed solution of sodium lactate, sodium chloride, potassium chloride and calcium chloride each having a fixed amount, which is a solution known in this technical field.
The pH regulator is an alkaline substance with the concentration of 0.1M-1M, preferably, natrium hydroxide, triethylamine, lysine, arginine or histidine.
In the novel local anesthetic analgesic sustained-release drug delivery system, the dosage of each of the ingredients has the following range:
5 ml of internal aqueous phase in total, including 5 mg-500 mg of analgesic, 1 ml-5 ml of drug solvent and 5 mg-500 mg of drug solubilizer; 100 ml of external aqueous phase in total, selected from an aqueous solution prepared from one or more of 0.01 g-10 g of saccharide, 0.1 g-10 g of ring-shaped organic acid, 0.1 g-10 g of organic base and 0.1 g-10 g of deflocculant; 5 ml of oil phase in total, including 5 mg-400 mg of synthetic phospholipid, 0.5 mg-250 mg of synthetic phosphatidylglycerol, 2.5 mg-250 mg of cholesterol and 2.5 mg-250 mg of glyceride; and the organic solvent, selected from one or more of 0.5 ml-50 ml of trichloromethane, 0.5 ml-50 ml of ethyl ether and 0.5 ml-50 ml of n-hexane.
Preferably, in the novel local anesthetic analgesic sustained-release drug delivery system, the dosage of each of the ingredients has the following range:
5 ml of internal aqueous phase in total, including 25 mg-300 mg of analgesic, 1 ml-5 ml of drug solvent and 25 mg-250 mg of drug solubilizer; 100 ml of external aqueous phase in total, selected from an aqueous solution prepared from one or more of 1 g-5 g of saccharide, 1 g-5 g of ring-shaped organic acid, 1 g-3 g of organic base and 1 g-5 g of deflocculant; 5 ml of oil phase in total, including 25 mg-150 mg of synthetic phospholipid, 5 mg-100 mg of synthetic phosphatidylglycerol, 5 mg-125 mg of cholesterol and 1 mg-150 mg of glyceride; and the organic solvent, selected from one or more of 1.5 ml-45 ml of trichloromethane, 1.5 ml-45 ml of ethyl ether and 1.5 ml-45 ml of n-hexane.
For the novel local anesthetic analgesic sustained-release drug delivery system, the preparation method comprises the following steps:
(1) Preparation of Internal Aqueous Phase
Weighing a certain amount of analgesic, and if the analgesic is in a free base form, adding a prescription amount of drug solvent and drug solubilizer to dissolve the analgesic completely; and if the analgesic is in an acid saline form, replacing the acid radical contained in the analgesic with an acid radical containing N or P, and then operating in accordance with the above-mentioned method.
(2) Preparation of External Aqueous Phase
Weighing a certain amount of substances of an external aqueous phase, and adding water to dissolve same, wherein the organic base is used to regulate the pH value of the external aqueous phase.
(3) Preparation of Oil Phase
Weighing a prescription amount of synthetic phosphatidylcholine, synthetic phosphatidylglycerol, cholesterol and glyceride, and dissolving same using an organic solvent to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase with the volume ratio of 1:10-10:1, and shearing for 5-20 min at 10000-16000 rpm to obtain primary emulsion.
5) Preparation of Multiple Emulsion
Weighing a certain amount of primary emulsion, adding the primary emulsion into the external aqueous phase in accordance with the phase volume ratio of 1:5-1:50 of the primary emulsion to the external aqueous phase, shearing for 5-60 s at 1000-4000 rpm, then sequentially adding external aqueous phase which is 5-20 times the volume of the primary emulsion rapidly, blowing for 5-30 min using 40-90 L/min of nitrogen at 20-40° C. or performing rotary evaporation at 20-40° C.; and removing the organic solvent, collecting the intermediate of the liposome, centrifuging for 10-30 min at 100-20000 rpm, discarding the supernatant, flushing using a large number of isoosmotic regulator, regulating the pH to 5.0-8.0 using the pH regulator, and obtaining a multivesicular liposome, the grain size of the obtained multivesicular liposome ranging from 1 μm to 50 μm.
On the premise of conforming to the basic idea in this field, preferable multivesicular liposome preparations may be obtained through any combination of the above-mentioned technical features.
The present invention has the advantageous effect that: the present invention proposes conditions that must be met for preparing a multivesicular liposome as a specific drug, due to different drug structures, the required drug solubilizers are different, the structure of local anesthetics of amide derivatives contains benzene ring, pyridine ring, so that if ring-shaped organic acids are selected as drug solubilizers, the effect may be preferable, in addition, because the pyridine ring contains N atoms, if inorganic acids containing N and P in the same family are selected as drug solubilizers, a multivesicular liposome of high yield may be prepared. The multivesicular liposome prepared in the present invention has the advantages of high encapsulation percentage and drug loading capacity, uniform grain size, and good sustained-release effect. The multivesicular liposome of the present invention may be used to prepare drugs for treating chronic diseases that require long-term administration such as antidiabetic drugs, antidepressive drugs, drugs for treating cardiovascular diseases and the like.
The present invention will be described below in detail in combination with drawings. Described embodiments are only used for explaining the present invention, but are not intended to limit the scope of the present invention.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing a certain amount of levobupivacaine hydrochloride, dissolving same in water and then adding 1M natrium hydroxide, filtering and collecting solid if there is no more insoluble substances, washing same with water for injection to neutral, drying at 60° C., adding other substances of the internal aqueous phase into the solid powder, adding 3 ml of 1M phosphoric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the nicotinic acid and sodium citrate of the external aqueous phase in the above table, adding 80 ml of water to dissolve same, regulating the pH to 7.4 using arginine, and adding water to 100 ml, to obtain an external aqueous phase.
(3) Preparation of Oil Phase
Weighing various substances of the oil phase in the above table, and dissolving same using 5 ml of mixed solution of trichloromethane and ethyl ether (with the volume ratio of 3:2) to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase, and shearing for 10 min at 13000 rpm to obtain primary emulsion.
(5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 20 ml of external aqueous phase, shearing for 60 s at 3000 rpm, sequentially adding 80 ml of external aqueous phase rapidly, blowing for 20 min using 80 L/min of nitrogen, removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of 0.9% NaCl solution, regulating the pH of the suspension of the liposome to 7.4 using 1M natrium hydroxide, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 30 μm.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing 200 mg of bupivacaine, adding other substances of the internal aqueous phase, adding 2.5 ml of 1M nitric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the glucuronic acid, cane sugar and sodium citrate of the external aqueous phase in the above table, adding 80 ml of water to dissolve same, regulating the pH to 8.0 using arginine, and adding water to 100 ml, to obtain an external aqueous phase.
(3) Preparation of Oil Phase
Weighing various substances of the oil phase in the above table, and dissolving same using 5 ml of mixed solution of trichloromethane and ethyl ether (with the volume ratio of 4:1) to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase, and shearing for 8 min at 16000 rpm to obtain primary emulsion.
5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 20 ml of external aqueous phase, shearing for 30 s at 2000 rpm, sequentially adding 80 ml of external aqueous phase rapidly, performing rotary evaporation at 35° C., removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of 5% dextrose solution, regulating the pH of the suspension of the liposome to 6.8 using 0.8M triethylamine, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 43 μm.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing 250 mg of ropivacaine, adding other substances of the internal aqueous phase, adding 3.5 ml of 1M phosphoric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the vitamin C, cane sugar and sodium tartrate of the external aqueous phase in the above table, adding 80 ml of water to dissolve same, regulating the pH to 8.5 using lysine, and adding water to 100 ml, to obtain an external aqueous phase.
(3) Preparation of Oil Phase
Weighing various substances of the oil phase in the above table, and dissolving same using 5 ml of trichloromethane to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase to the oil phase, and shearing for 10 min at 13000 rpm to obtain primary emulsion.
(5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 20 ml of external aqueous phase, shearing for 15 s at 3000 rpm, sequentially adding 80 ml of external aqueous phase rapidly, performing rotary evaporation at 37° C., removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of 5% mannitol solution, regulating the pH of the suspension of the liposome to 7.2 using 0.2M lysine, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 24 μm.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing 300 mg of lidocaine, adding other substances of the internal aqueous phase, adding 4 ml of 1M nitric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the vitamin C, glucuronic acid, sodium dihydrogen phosphate and dextrose of the external aqueous phase in the above table, adding 80 ml of water to dissolve same, regulating the pH to 9.0 using histidine, and adding water to 100 ml, to obtain an external aqueous phase.
(3) Preparation of Oil Phase
Weighing various substances of the oil phase in the above table, and dissolving same using 5 ml of mixed solution of trichloromethane and ethyl ether (with the volume ratio of 1:4) to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase, and shearing for 10 min at 10000 rpm to obtain primary emulsion.
(5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 20 ml of external aqueous phase, shearing for 15 s at 4000 rpm, sequentially adding 80 ml of external aqueous phase rapidly, water bathing at 35° C., blowing for 15 min using 100 L/min of nitrogen, removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of sodium lactate ringer's solution, regulating the pH of the suspension of the liposome to 7.4 using 0.5M arginine, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 45 μm.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing 180 mg of mepivacaine, adding other substances of the internal aqueous phase, adding 3 ml of 1M phosphoric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the glucuronic acid and disodium hydrogen phosphate of the external aqueous phase in the above table, adding 100 ml of water to dissolve same, regulating the pH to 7.0 using lysine, adding water to 150 ml, to obtain an external aqueous phase.
(3) Preparation of Oil Phase
Weighing various substances of the oil phase in the above table, dissolving same using 5 ml of mixed solution of n-hexane and ethyl ether (with the volume ratio of 3:2) to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase, and shearing for 20 min at 16000 rpm to obtain primary emulsion.
(5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 30 ml of external aqueous phase, shearing for 60 s at 4000 rpm, sequentially adding 120 ml of external aqueous phase rapidly, water bathing at 30° C., performing rotary evaporation, removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of 5% dextrose solution, and regulating the pH of the suspension of the liposome to 7.4 using 0.2M histidine, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 15 nm.
Prescription Ingredients
The preparation method of the multivesicular liposome is as follows:
(1) Preparation of Internal Aqueous Phase
Weighing 220 mg of levobupivacaine, adding other substances of the internal aqueous phase, adding 2 ml of 1M phosphoric acid, dissolving same and then adding water to 5 ml, to obtain an aqueous phase.
(2) Preparation of External Aqueous Phase
Weighing the vitamin C, cane sugar, disodium hydrogen phosphate and sodium dihydrogen phosphate of the external aqueous phase in the above table, adding 100 ml of water to dissolve same, regulating the pH to 7.0 using arginine, and adding water to 150 ml, to obtain an external aqueous phase.
Weighing various substances of the oil phase in the above table, and dissolving same using 5 ml of mixed solution of n-hexane and trichloromethane (with the volume ratio of 3:2) to obtain an oil phase.
(4) Preparation of Primary Emulsion
Adding the prepared internal aqueous phase into the oil phase, and shearing for 10 min at15000 rpm to obtain primary emulsion.
5) Preparation of Multiple Emulsion
Weighing 5 ml of primary emulsion, rapidly pouring 30 ml of external aqueous phase, shearing for 25 s at 8000 rpm, sequentially adding 120 ml of external aqueous phase rapidly, water bathing at 35° C., performing rotary evaporation, removing the organic solvent, collecting the intermediate of the multivesicular liposome, flushing using a large number of 0.9% sodium chloride solution, regulating the pH of the suspension of the liposome to 7.0 using 0.1M natrium hydroxide, and obtaining the multivesicular liposome, the mean grain size of the obtained multivesicular liposome being 18 μm.
Microstructure Observation of Levobupivacaine Multivesicular Liposome
The levobupivacaine multivesicular liposome is prepared in accordance with the above-mentioned embodiment 1: take a drop of multivesicular liposome on the glass slide, cover the cover slip, observe under 400× microscope and 200× microscope, and shoot the microstructure diagram of the levobupivacaine multivesicular liposome, as shown in
Determination of Content and Encapsulation Percentage of Levobupivacaine Multivesicular Liposome
The content of the levobupivacaine multivesicular liposome is determined using high performance liquid chromatography, wherein the chromatographic conditions are as follows:
Chromatographic column: Agilent C18 column (150 mm*4.6 mm*5 μm); The mixed solution of 0.02 mol/L phosphate buffered saline (weighing 2.72 g of potassium dihydrogen phosphate and 0.75 g of natrium hydroxide, adding 1000 ml of water to dissolve same, and regulating the pH value to 8.0)-acetonitrile (50:50) is used as a mobile phase; the detection wavelength is 240 nm; the flow velocity is 1.0 ml/min; the column temperature is 35° C., and the injection volume is 20 μl. The resolution between the levobupivacaine peak and an impurity peak adjacent thereto should be greater than 1.5.
The specific method for determination of the encapsulation percentage of the levobupivacaine multivesicular liposome is as follows:
precisely measuring 1.0 ml of suspension of levobupivacaine multivesicular liposome, adding 1.0 ml of 0.9% NaCl solution, precisely transferring 0.1 ml after blending, placing same in 10 ml of volumetric flask, adding 2 ml of methanol, performing demulsification and vibration and diluting same to the scale using the mobile phase, and shaking well; determining the total dosage (Wtotal) in the levobupivacaine multivesicular liposome using HPLC; centrifuging other samples for 10 min at 3000 rpm, precisely transferring 0.1 ml of supernatant, placing same in 10 ml of volumetric flask, adding 2 ml of methanol to perform demulsification and vibration, diluting same to the scale using the mobile phase, shaking well, sucking 20 μl, operating in accordance with the above-mentioned chromatographic condition, and determining the content of free drug in the levobupivacaine multivesicular liposome (Wsupernatant).
The encapsulation percentage (EE %) of the levobupivacaine multivesicular liposome is computed in accordance with the formula: encapsulation percentage (EE %)=(Wtotal−Wsupernatant)/Wtotal×100%. The encapsulation percentage of the multivesicular liposome in the embodiment is determined in accordance with the above-mentioned method, see the following table:
Pesticide Effect Comparison of Levobupivacaine Multivesicular Liposome
30-week guinea pigs which are 300-500 g in weight and are male are used as experimental animals. Before the experiment, the guinea pigs should have a rest-cure for 3 days in an independent environment at the room temperature of (23±1)° C. under 12-12 h bright/dark illumination (illumination is at 8:00 a.m) to adapt to the environment.
Experimental method: the hair on 6 cm×10 cm of back skin of guinea pigs (nine) is completely shaved. The herpes range is marked, and 4 regions are marked for each guinea pig, wherein the upper left region indicates normal saline, the upper right region indicates blank multivesicular liposome, the left lower region indicates levobupivacaine hydrochloride injection, and the lower right region indicates self-control levobupivacaine multivesicular liposome. The experiment is divided into three dosage groups, i.e. low dosage group 10 mg/ml, middle dosage group 15 mg/ml, and high dosage group 20 mg/ml, each group including three guinea pigs. The injection volume of intradermal injection for administration of each marked region is 0.35 ml. Subcutaneous herpes is formed, and the response of the guinea pigs to acupuncture is tested after 15 min. Each herpes is acupunctured for 17 times, wherein the acupuncture interval is 3-5 s, and the test time point are respectively: 1 min, 15 min, 30 min, 3 h, 6 h, 9 h, 12 h, 18 h, 21 h, 24 h, 30 h and 48 h after injection, 12 time points in total. Each guinea pig is acupunctured for 204 times in total in each region, and the acupuncture to which the guinea pigs cannot respond is counted. The number of acupuncture not making a response at the 12 time points within 48 h is accumulated, and the degree of anesthesia is reflected through the value formed by taking the sum as a numerator and the total acupuncture number 204 as a denominator. The mean percentage of number of times of non-response of each group of guinea pigs is computed, the bigger the value is, the stronger the anesthetic effect is; the smaller the computation value is, the weaker the anesthetic effect is. See Table 1 and
The pharmacodynamic experiment of the levobupivacaine multivesicular liposome demonstrates that the acupuncture painless response number (10 mg/ml: 79.90%; 13.3 mg/ml: 82.35%; 20 mg/ml: 85.78% respectively) of the levobupivacaine multivesicular liposome within 48 hours is apparently higher than that of levobupivacaine hydrochloride injection (28.59%), and the action duration is greater than 24 hours. Therefore, it can be implemented that levobupivacaine is prepared into multivesicular liposome suspension with a sustained release function and then is used for postoperative analgesia.
The above is just preferred embodiments of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and the principle of the present invention shall be contained within the protection scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201810320900.2 | Apr 2018 | CN | national |
This application is a continuation of International Application No. PCT/CN2018/083447 with a filing date of Apr. 18, 2018, designating the United States, now pending, and further claims to Chinese application no. 201810320900.2 with a filing date of Apr. 11, 2018. The content of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2018/083447 | Apr 2018 | US |
| Child | 16106414 | US |
