Preparation method and application of pH response type enrofloxacin granules for treating porcine respiratory bacterial mixed infection

Abstract

The invention belongs to the technical field of veterinary drugs, and discloses a preparation method and application of pH response type enrofloxacin granules for treating porcine respiratory bacterial mixed infection. The invention provides the enrofloxacin coated particle, the enrofloxacin coated particle has pH response capability, is not released in a stomach pH environment and can be quickly released in a near small intestine pH environment, so that the stomach irritation of enrofloxacin is reduced, and the enrofloxacin is ensured to be absorbed at an optimal part. According to the enrofloxacin coated granules, the bitter taste of the medicine is effectively covered, the administration frequency is reduced, and the effective plasma concentration maintaining time is prolonged. Meanwhile, the enrofloxacin coated granules have a good treatment effect on porcine respiratory diseases caused by mixed infection of various bacteria.

Description

Technical Field

[0001] This invention belongs to the field of veterinary drug technology, specifically relating to a method for preparing pH-responsive enrofloxacin granules for treating mixed bacterial respiratory infections in pigs and their application. Background Technology

[0002] Swine respiratory disease syndrome (SRS) is a common disease in pig farming, primarily caused by a combination of factors including bacteria, viruses, mycoplasma, and environmental stress. Mixed infections with bacterial pathogens such as Actinobacillus pleuropneumoniae, Pasteurella multocida, and Streptococcus are particularly prevalent. This disease is widespread globally, with a morbidity rate of 30%–70%, leading not only to stunted growth and reduced feed efficiency but also to increased mortality, causing significant economic losses to the pig farming industry. Enrofloxacin, an animal-specific fluoroquinolone antibiotic, has become an important drug for the clinical treatment of mixed respiratory infections in pigs due to its broad-spectrum antibacterial activity and excellent tissue penetration.

[0003] Enrofloxacin exerts its bactericidal effect by inhibiting bacterial DNA gyrases (topoisomerase II) and topoisomerase IV, thereby blocking bacterial DNA replication and repair. Currently, commonly used formulations in veterinary clinical practice include injections, granules, soluble powders, and regular powders. However, traditional formulations have significant limitations: injections are difficult to administer and are invasive, easily leading to stress; the bioavailability of soluble powders is significantly affected by drinking habits, and the drug is eliminated rapidly in the body (half-life of approximately 4-6 hours), requiring 2-3 daily doses to maintain effective blood concentrations; while regular granules can reduce enrofloxacin dissolution in the oral cavity to some extent, they still cannot solve the palatability problem. These shortcomings result in poor clinical adherence to enrofloxacin, high treatment costs, and a high risk of inducing drug resistance.

[0004] pH-responsive granules offer significant advantages in improving drug palatability and enhancing efficacy. This formulation utilizes suitable pH-responsive materials (such as polyacrylic acid resin and hydroxypropyl methylcellulose phthalate) and employs techniques like melt extrusion, fluidized bed coating, or matrix molding to construct a delivery system with specific drug release characteristics. This design minimizes drug release in the gastric environment, reducing irritation, and allows for rapid disintegration and release in the intestines, maintaining effective blood drug concentrations for 12-24 hours, enabling once-daily dosing. Simultaneously, coating technology significantly improves palatability, increasing the willingness of pigs to consume feed. Furthermore, pH-responsive granules can reduce toxic side effects and improve the therapeutic index. Compared to traditional formulations, pH-responsive granules offer significant advantages in terms of convenience of group dosing, drug safety, and stability of therapeutic effects. Currently, most publicly disclosed enrofloxacin formulation patents are for sustained-release or controlled-release formulations, such as those using enrofloxacin and fenugreek as raw materials. These inclusion complexes offer advantages such as delayed drug release, reduced clinical dosing frequency, improved product stability, and enhanced palatability. Water-emulsion particles obtained by solution spray granulation effectively mask the bitter taste and odor of enrofloxacin. They are also water-soluble and, after oral administration, exhibit high absolute bioavailability, high blood concentration, rapid absorption, rapid clearance, and wide distribution. Veterinary enrofloxacin solid lipid nanosuspension possesses a significant sustained-release effect, enhancing in vivo absorption and cellular uptake of active molecules, reducing the frequency of clinical dosing, and is non-irritating to target animals. It can be used to prevent and treat bacterial digestive and respiratory diseases in pigs and chickens.

[0005] However, there are currently few publicly reported cases of using pH-responsive enrofloxacin granules for the prevention and treatment of mixed respiratory infections in pigs. Therefore, there is an urgent need to develop a pH-responsive enrofloxacin granule formulation that can achieve targeted release at the intestinal pH, has good palatability, and is easily absorbed orally for group administration. This is crucial for improving the prevention and treatment efficiency of mixed bacterial respiratory infections in pigs and reducing medication costs. The development of this formulation will fill a technological gap and provide the livestock industry with a safer and more efficient medication option. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art. It provides a pH-responsive enrofloxacin granule formulation that, through a specific delivery system and design, effectively masks the bitter taste of the drug, reduces the gastric irritation of enrofloxacin, and prolongs the duration of effective blood drug concentration.

[0007] The first objective of this invention is to provide enrofloxacin-coated granules.

[0008] The second objective of this invention is to provide a method for preparing enrofloxacin-coated particles according to the first aspect of this invention.

[0009] The third aspect of this invention aims to provide the application of enrofloxacin-coated particles from the first aspect of this invention in the preparation of products.

[0010] The fourth aspect of this invention is to provide a product.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] In a first aspect, the present invention provides enrofloxacin-coated granules, which are made from raw materials comprising: enrofloxacin, filler, binder, disintegrant, glidant and coating material.

[0013] In some embodiments of the present invention, the filler includes at least one selected from glucose, lactose, sucrose, microcrystalline cellulose, starch, arabinose, trehalose, ribose, raffinose, isomaltol, lactitol, maltose, mannitol, and sorbitol; preferably glucose and lactose.

[0014] In some embodiments of the present invention, the adhesive comprises at least one of polyvinylpyrrolidone, polyethylene glycol (such as polyethylene glycol 4000, polyethylene glycol 6000), dextrin, gelatin, polyvinylpyrrolidone, methylcellulose, ethylcellulose and starch; preferably polyvinylpyrrolidone (such as polyvinylpyrrolidone K30, polyvinylpyrrolidone K60 and / or polyvinylpyrrolidone K90, etc.).

[0015] In some embodiments of the present invention, the disintegrant includes at least one of croscarmellose sodium, sodium carboxymethyl starch, sodium carboxymethyl cellulose, and hydroxypropyl methylcellulose; preferably croscarmellose sodium and / or sodium carboxymethyl starch.

[0016] In some embodiments of the present invention, the flow aid includes at least one of silica, magnesium stearate, calcium stearate and talc; preferably silica (such as colloidal silica) or magnesium stearate.

[0017] In some embodiments of the present invention, the coating material includes at least one of ethyl cellulose, cellulose acetate, hydroxypropyl methylcellulose phthalate, polyvinylpyrrolidone, acrylic resin (such as acrylic resin III or IV), polyacrylic resin, and cyclodextrin; preferably hydroxypropyl methylcellulose phthalate and / or polyacrylic resin.

[0018] In some embodiments of the present invention, the hydroxypropyl methylcellulose phthalate (HPMCP) includes at least one of HPMCPHP-50, HPMCCP HP-55, and HPMCCP HP-55S.

[0019] In some embodiments of the present invention, the polyacrylic resin includes polyacrylic resin I and polyacrylic resin II.

[0020] In some embodiments of the present invention, the polyacrylic resin I includes the Eudragit L series (such as Eudragit L100, Eudragit L100-55), the Eudragit S series (such as Eudragit S100), and the Eudragit E series (such as E PO, E 100).

[0021] In some embodiments of the present invention, the coating material comprises hydroxypropyl methylcellulose phthalate and polyacrylic acid resin I, with a mass ratio of 1:(1~3), such as any value of 1:1, 1:2 and 1:3 or any range formed by both.

[0022] In some embodiments of the present invention, the coating material further includes at least one of triethyl citrate, acetylated triethyl citrate, tributyl citrate, dibutyl phthalate, dioctyl phthalate, and ethylparaben.

[0023] In some embodiments of the present invention, the amount of plasticizer is 0% to 20% of the mass of the coating material, such as any value or a range formed by any two of 0%, 2%, 4%, 6%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0024] In some embodiments of the present invention, the raw material comprises 1 to 30 parts by weight of enrofloxacin.

[0025] In some embodiments of the present invention, the raw material comprises 5 to 20 parts of enrofloxacin by weight, such as any value or a range formed by any two of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 parts.

[0026] In some embodiments of the present invention, the raw material comprises 40 to 90 parts by weight of filler.

[0027] In some embodiments of the present invention, the raw material comprises 60 to 90 parts by weight of filler, such as any value or a range formed by any two of the following: 60, 62, 64, 66, 68, 70, 72, 74, 75.5, 76, 78, 78.5, 79, 80, 81.5, 82, 82.5, 84, 86, 88, or 90 parts.

[0028] In some embodiments of the present invention, the raw material comprises 1 to 10 parts of adhesive by weight.

[0029] In some embodiments of the present invention, the raw material comprises 1 to 6 parts by weight of adhesive, such as any value of 1, 2, 3, 4, 5 or 6 parts or a range formed by any two of them.

[0030] In some embodiments of the present invention, the raw material includes 1 to 15 parts of disintegrant.

[0031] In some embodiments of the present invention, the raw material comprises 1 to 10 parts of disintegrant, such as any value of 1, 2, 3, 4, 5, 6, 7, 7.5, 8, 9 or 10 parts or a range formed by any two of them.

[0032] In some embodiments of the present invention, the raw material includes 0.1 to 2 parts of a flow aid.

[0033] In some embodiments of the present invention, the raw material includes 0.1 to 1 part of a flow aid, such as any value or a range formed by any two of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1 part.

[0034] In some embodiments of the present invention, the raw material comprises 1 to 10 parts by weight of coating material.

[0035] In some embodiments of the present invention, the raw material comprises 2 to 5 parts by weight of coating material, such as any value of 2, 3, 4 or 5 parts or a range formed by any two of them.

[0036] In some embodiments of the present invention, the enrofloxacin-coated particles are made from raw materials including: enrofloxacin, glucose, lactose, sodium carboxymethyl starch, polyvinylpyrrolidone, cross-linked sodium carboxymethyl cellulose, colloidal silica, and coating material.

[0037] In some embodiments of the present invention, the enrofloxacin-coated granules, by weight, are made from the following raw materials: 5-20 parts enrofloxacin, 5-75 parts glucose, 8-80 parts lactose, 2-6 parts sodium carboxymethyl starch, 1-6 parts polyvinylpyrrolidone, 1-5 parts cross-linked sodium carboxymethyl cellulose, 0.1-1 parts colloidal silica / magnesium stearate, and 2-5 parts coating material.

[0038] In some embodiments of the present invention, the enrofloxacin-coated granules, by weight, are made from the following raw materials: 5-15 parts enrofloxacin, 5-68 parts glucose, 10-75 parts lactose, 2-5 parts sodium carboxymethyl starch, 2-5 parts polyvinylpyrrolidone, 2-4 parts croscarmellose sodium, 0.3-0.7 parts colloidal silica / magnesium stearate, and 2-5 parts coating material.

[0039] The enrofloxacin coated granules provided by this invention can overcome the problems of frequent administration, poor palatability affecting pig feed intake, and gastrointestinal irritation of existing ordinary enrofloxacin preparations. They can achieve continuous and efficient inhibition of mixed respiratory pathogens in pigs under once-daily administration, thereby improving clinical medication compliance and treatment efficacy.

[0040] A second aspect of the present invention provides a method for preparing enrofloxacin-coated particles according to the first aspect of the present invention, comprising the following steps: Enrofloxacin, filler, and partial disintegrant are mixed to obtain a mixture; The solution containing the binder is mixed with the mixture and granulated to obtain granules (1). Particles (1) are mixed with the remaining disintegrant and glidant to obtain particles (2); The particles (2) were coated with a coating material to obtain enrofloxacin coated particles.

[0041] In some embodiments of the present invention, the solvent of the adhesive-containing solution is water.

[0042] In some embodiments of the present invention, the granulation time is 3 to 5 minutes.

[0043] In some embodiments of the present invention, the particles (1) are dried and sieved before being mixed with disintegrants and flow aids.

[0044] In some embodiments of the present invention, the drying process is carried out until the moisture content is <2%.

[0045] In some embodiments of the present invention, the drying temperature is 45~60°C, such as any value or a range formed by any two of 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 or 60°C.

[0046] In some embodiments of the present invention, the frequency of the drying fan is 10~35Hz.

[0047] In some embodiments of the present invention, the drying time is 40 to 80 minutes, such as any value of 40, 45, 50, 55, 60, 65, 70, 75 or 80 minutes or a range formed by any two of them.

[0048] In some embodiments of the present invention, the sieving process includes passing the dried particles through 16-mesh and 80-mesh sieves in sequence to collect particles of 16-mesh to 80-mesh.

[0049] In some embodiments of the present invention, the mixing conditions for the particles (1) with the remaining disintegrant and glidant are 15-30 rpm for 5-15 min; further, 20-25 rpm for 10-15 min.

[0050] In some embodiments of the present invention, the coating material is dissolved in ethanol before the coating treatment.

[0051] In some embodiments of the present invention, the coating treatment includes the following steps: using a solution containing coating material to perform bottom spray coating on particles (2) in a fluidized bed, with a spraying speed of 5~30mL / min and an atomization pressure of 0.1~1mPa.

[0052] In some embodiments of the present invention, the spraying rate is 10 to 20 mL / min, such as any value or a range formed by any two of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 mL / min.

[0053] In some embodiments of the present invention, the atomizing pressure is 0.1~0.6 mPa, such as any value of 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6 mPa or a range formed by any two of them.

[0054] In some embodiments of the present invention, during the coating process, the inlet air temperature is 50~60°C, such as any value or a range formed by any two of 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 or 60°C.

[0055] In some embodiments of the present invention, the rotation speed is set to 20-30 rpm during the coating process, such as any value or a range formed by any two of 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 rpm.

[0056] In some embodiments of the present invention, a drying step is further included after the coating treatment.

[0057] In some embodiments of the present invention, the drying process is carried out until the moisture content is <2%.

[0058] In some embodiments of the present invention, the drying temperature is 45~60°C, such as any value or a range formed by any two of 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 or 60°C.

[0059] In some embodiments of the present invention, the frequency of the drying fan is 10~35Hz.

[0060] In some embodiments of the present invention, the drying time is 40 to 80 minutes, such as any value of 40, 45, 50, 55, 60, 65, 70, 75 or 80 minutes or a range formed by any two of them.

[0061] A third aspect of the present invention provides the application of enrofloxacin-coated particles from the first aspect of the present invention in the preparation of products.

[0062] In some embodiments of the present invention, the product includes at least one of a drug, feed, and feed additive.

[0063] In some embodiments of the present invention, the product has at least one of the following functions: inhibiting pathogenic microorganisms and treating diseases caused by pathogenic microorganisms.

[0064] In some embodiments of the present invention, the pathogenic microorganism includes at least one of mycoplasma, Escherichia coli, Salmonella, Staphylococcus, Pasteurella, Aeromonas, Vibrio, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PPRSV), porcine circovirus (PCV), classical swine fever virus (CSFV), and pseudorabies virus (PRV).

[0065] In some embodiments of the present invention, the diseases include, but are not limited to, piglet yellow scours, white scours, and edema disease; respiratory and digestive tract infections such as swine mycoplasma pneumonia, swine pneumonia, and paratyphoid fever; enteritis and septicemia; preferably, mixed bacterial infections of the swine respiratory tract.

[0066] A fourth aspect of the present invention provides a product comprising enrofloxacin-coated granules according to the first aspect of the present invention.

[0067] In some embodiments of the present invention, the product includes at least one of a drug, feed, and feed additive.

[0068] In some embodiments of the present invention, the product has at least one of the following functions: inhibiting pathogenic microorganisms and treating diseases caused by pathogenic microorganisms.

[0069] In some embodiments of the present invention, the pathogenic microorganism includes at least one of mycoplasma, Escherichia coli, Salmonella, Staphylococcus, Pasteurella, Aeromonas, Vibrio, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, African swine fever virus (ASFV), porcine reproductive and respiratory syndrome virus (PPRSV), porcine circovirus (PCV), classical swine fever virus (CSFV), and pseudorabies virus (PRV).

[0070] In some embodiments of the present invention, the diseases include, but are not limited to, piglet yellow scours, white scours, and edema disease; respiratory and digestive tract infections such as swine mycoplasma pneumonia, swine pneumonia, and paratyphoid fever; enteritis and septicemia; preferably, mixed bacterial infections of the swine respiratory tract.

[0071] The beneficial effects of this invention are: This invention provides enrofloxacin-coated granules that are pH-responsive, meaning they are not released in the gastric pH environment but are rapidly released in the proximal small intestine pH environment. This reduces the gastric irritation of enrofloxacin and ensures that it is absorbed at the optimal site. The enrofloxacin-coated granules effectively mask the bitter taste of the drug, reduce the frequency of administration, and prolong the duration of effective blood drug concentration. Furthermore, these enrofloxacin-coated granules have a good therapeutic effect on respiratory diseases in pigs caused by mixed infections of multiple bacteria. Attached Figure Description

[0072] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 The results show the particle size analysis of the enrofloxacin-coated particles in Experiments 1-4.

[0073] Figure 2 The results of the dissolution of enrofloxacin-coated particles in Experiments 1-4 under simulated gastrointestinal pH conditions are shown in (a) for cumulative dissolution at pH 1.2, (b) for cumulative dissolution at pH 4.3, and (c) for cumulative dissolution at pH 6.8.

[0074] Figure 3 The images show the appearance of pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Experimental Example 4), commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C. A, B, and C in the images correspond to pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Experimental Example 4), commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C, respectively.

[0075] Figure 4 The results show the particle size distribution of pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Experimental Example 4), commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C.

[0076] Figure 5 The figures show the dissolution results of pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Experimental Example 4), commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C in a simulated gastrointestinal pH environment. (a) shows the cumulative dissolution rate of enrofloxacin at pH 1.2, (b) shows the cumulative dissolution rate of enrofloxacin at pH 4.3, and (c) shows the cumulative dissolution rate of enrofloxacin at pH 6.8. In the figure, A, B, and C correspond to pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Experimental Example 4), commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C, respectively.

[0077] Figure 6 The palatability test results of the enrofloxacin-coated granules in Example 1 are shown below. (a) shows the average feed intake at a concentration of 5 g / kg, (b) shows the average feed intake rate at a concentration of 5 g / kg, (c) shows the average feed intake at a concentration of 10 g / kg, (d) shows the average feed intake rate at a concentration of 10 g / kg, (e) shows the average feed intake at a concentration of 20 g / kg, and (f) shows the average feed intake rate at a concentration of 20 g / kg. In the figure, A, B, C, and D correspond to pH-responsive enrofloxacin granule A (i.e., the enrofloxacin-coated granules of Example 4), commercially available enrofloxacin granule B, commercially available enrofloxacin granule C, and the positive control drug, respectively.

[0078] Figure 7 The pharmacokinetic results of the three types of enrofloxacin granules in pigs used in Example 2 are shown in (a) as drug-time curves and (b) as AUC0-t statistical results. In the figure, A, B, and C correspond to pH-responsive enrofloxacin granule A (i.e., the enrofloxacin-coated granules of Example 4), commercially available enrofloxacin granule B, and commercially available enrofloxacin granule C, respectively.

[0079] Figure 8 To assess the efficacy of the three enrofloxacin granules used in Example 3 for treating respiratory diseases, (a) shows the qPCR analysis results of the pathogens, (b) shows the average daily feed intake and standard feed intake of the experimental pig herd, (c) shows the daily number of sick pigs in the experimental pig herd, and (d) shows the daily incidence rate of the experimental pig herd. Detailed Implementation

[0080] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0081] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0082] The term "fluidized bed bottom spray coating" refers to a process in fluidized bed equipment where the nozzle is located at the bottom, and the coating liquid is sprayed from bottom to top, making contact with the particles suspended in the fluidized air in the same direction to complete the coating.

[0083] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0084] Example 1 An enrofloxacin-coated granule, by mass percentage, comprises 10% enrofloxacin, 69.7% lactose, 6.3% anhydrous glucose, 4% sodium carboxymethyl starch, 3% polyvinylpyrrolidone K30, 3.5% croscarmellose sodium, 0.5% colloidal silica, and 3% coating material (Eudragit L100-55: triethyl citrate = 9:1 (w / w)).

[0085] The above-mentioned enrofloxacin-coated granules were prepared by the following method: 1. Add enrofloxacin, lactose, anhydrous glucose, and sodium carboxymethyl starch into a wet granulator in equal increments according to the prescription. Close the granulation pot lid, set the cutter speed to 1000 rpm, the stirring paddle speed to 120 rpm, and the mixing time to 5 min for premixing to obtain mixture (1). 2. Dissolve polyvinylpyrrolidone K30 in water to prepare a 3% (w / v) aqueous solution of polyvinylpyrrolidone K30, and obtain solution (1); 3. Add solution (1) into the granulation pot through a spray gun to granulate the mixture (1) for 3~5 minutes to obtain wet granules (1). 4. The prepared wet granules (1) are transported to a fluidized bed. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, a sample is taken and the moisture content is tested with a moisture analyzer. When the moisture content is <2%, the drying is stopped and dry granules (1) are obtained. 5. Discharge the dry granules (1) into a square vibrating screen. Set the first layer of screen mesh to 16 mesh and the second layer of screen mesh to 80 mesh. Qualified granules of 16 mesh to 80 mesh are obtained as dry granules (2). 6. Place the dry granules (2), the prescribed amount of cross-linked sodium carboxymethyl cellulose, and colloidal silica in a mixer, rotate at 20 rpm, and mix for 10 min to obtain dry granules (3). 7. Prepare a 6% (w / v) solution of the prescribed amount of coating material (Eudragit L100-55: triethyl citrate = 9:1 (w / w)) with 75% ethanol and use it to coat the dry particles (3) by fluidized bed bottom spray coating. Control the air inlet temperature at 55℃, the spraying speed at 15mL / min, the atomization pressure at 0.4mPa, the pot rotation speed at 25rpm, and the target coating weight gain at 5% to obtain coated wet particles (1). 8. Dry the coated wet granules (1) in a fluidized bed at 55℃. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, take a sample and test the moisture content with a moisture analyzer. Stop drying when the moisture content is <2%, and then the enrofloxacin coated granules are obtained.

[0086] Example 2 An enrofloxacin-coated granule, by mass percentage, comprises 10% enrofloxacin, 66.9% glucose, 11.6% lactose, 4.0% sodium carboxymethyl starch, 4% polyvinylpyrrolidone K30, 0.5% magnesium stearate, and 3% coating material (HPMCP HP-50 and triethyl citrate = 8.5:1.5 (w / w)).

[0087] The above-mentioned enrofloxacin-coated granules were prepared by the following method: 1. Add enrofloxacin, glucose, lactose, and sodium carboxymethyl starch into a wet granulator in equal increments according to the prescription. Close the granulation pot lid, set the cutter speed to 1000 rpm, the stirring paddle speed to 120 rpm, and the mixing time to 5 min for premixing to obtain mixture (1). 2. Dissolve polyvinylpyrrolidone K60 in water to prepare a 4% (w / v) polyvinylpyrrolidone K60 aqueous solution, and obtain solution (1). 3. Add solution (1) into the granulation pot through a spray gun to granulate the mixture (1) for 3~5 minutes to obtain wet granules (1). 4. The prepared wet granules (1) are transported to a fluidized bed. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, a sample is taken and the moisture content is tested with a moisture analyzer. When the moisture content is <2%, the drying is stopped and dry granules (1) are obtained. 5. Discharge the dry granules (1) into a square vibrating screen. Set the first layer of screen mesh to 16 mesh and the second layer of screen mesh to 80 mesh. Collect qualified granules of 16 mesh to 80 mesh to obtain dry granules (2). 6. Place the dry granules (2), the remaining 2.0% sodium carboxymethyl starch, and 0.5% magnesium stearate into a mixer, mix at 20 rpm for 10 min to obtain dry granules (3). 7. Prepare a 6% (w / v) solution of coating material (HPMCP HP-50: triethyl citrate = 8.5:1.5 (w / w)) with 75% ethanol and apply it to the dry particles (3) by fluidized bed bottom spray coating. Control the air inlet temperature at 55℃, the spraying speed at 15mL / min, the atomization pressure at 0.4 mPa, the pot rotation speed at 25 rpm, and the target coating weight gain at 5% to obtain wet coated particles (1). 8. Dry the coated wet granules (1) in a fluidized bed at 55℃. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, take a sample and test the moisture content with a moisture analyzer. Stop drying when the moisture content is <2%, and then the enrofloxacin coated granules are obtained.

[0088] Example 3 An enrofloxacin-coated granule, by mass percentage, comprises 10% enrofloxacin, 40% glucose, 38.5% lactose, 2.0% croscarmellose sodium, 3% polyvinylpyrrolidone K30, 3.0% sodium carboxymethyl starch, 0.5% colloidal silica, and 3% coating material (Eudragit L100-55: HPMCP HP-50 = 1:1 (w / w)).

[0089] The above-mentioned enrofloxacin-coated granules were prepared by the following method: 1. Add enrofloxacin, glucose, lactose and croscarmellose sodium into a wet granulator in equal increments according to the prescription. Close the granulation pot lid, set the cutter speed to 1000 rpm, the stirring paddle speed to 120 rpm, and the mixing time to 5 min for premixing to obtain mixture (1). 2. Dissolve polyvinylpyrrolidone K30 in water to prepare a 3% (w / v) aqueous solution of polyvinylpyrrolidone K30, and obtain solution (1); 3. Add the solution (1) into the granulation pot through the spray gun and granulate the mixture (1) for 3~5 minutes to obtain wet granules (1). 4. The prepared wet granules (1) are transported to a fluidized bed. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, a sample is taken and the moisture content is tested with a moisture analyzer. When the moisture content is <2%, the drying is stopped and dry granules (1) are obtained. 5. Discharge the dry granules (1) into a square vibrating screen. Set the first layer of screen mesh to 16 mesh and the second layer of screen mesh to 80 mesh. Collect qualified granules of 16 mesh to 80 mesh to obtain dry granules (2). 6. Place the dry granules (2), the prescribed amount of sodium carboxymethyl starch, and colloidal silica in a mixer at a speed of 20 rpm and mix for 10 min to obtain dry granules (3). 7. Prepare a 6% (v / w) solution of coating material (Eudragit L100-55: HPMCP HP-50 = 1:1 (w / w)) with 75% ethanol and apply it to the dry particles (3) by fluidized bed bottom spray coating. Control the air inlet temperature at 55℃, the spraying speed at 15mL / min, the atomization pressure at 0.4 mPa, the pot rotation speed at 25 rpm, and the target coating weight gain at 5% to obtain wet coated particles (1). 8. Dry the wet-coated granules (1) in a fluidized bed at 55℃. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, take a sample and test the moisture content with a moisture analyzer. Stop drying when the moisture content is <2%, and then obtain enrofloxacin coated granules.

[0090] Example 4 An enrofloxacin-coated granule, by mass percentage, comprises 10% enrofloxacin, 21% glucose, 54.5% lactose, 4.0% sodium carboxymethyl starch, 3% polyvinylpyrrolidone K30, 4.0% crosslinked sodium carboxymethyl cellulose, 0.5% colloidal silica, and 3% coating material (Eudragit L100-55: HPMCP HP-50 = 1:1 (w / w)).

[0091] The above-mentioned enrofloxacin-coated granules were prepared by the following method: 1. Add enrofloxacin, glucose, lactose, and sodium carboxymethyl starch into a wet granulator in equal increments according to the prescription. Close the granulation pot lid, set the cutter speed to 1000 rpm, the stirring paddle speed to 120 rpm, and the mixing time to 5 min for premixing to obtain mixture (1). 2. Dissolve polyvinylpyrrolidone K30 in water to prepare a 3% (w / v) aqueous solution of polyvinylpyrrolidone K30, and obtain solution (1); 3. Add solution (1) into the granulation pot through a spray gun to granulate the mixture (1) for 3 minutes to obtain wet granules (1). 4. The wet granules (1) are transported to the fluidized bed. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, a sample is taken and the moisture content is tested with a moisture analyzer. When the moisture content is <2%, the drying is stopped and dry granules (1) are obtained. 5. Discharge the dry granules (1) into a square vibrating screen. Set the first layer of screen mesh to 16 mesh and the second layer of screen mesh to 80 mesh. Collect qualified granules of 16 mesh to 80 mesh to obtain dry granules (2). 6. Place the dry granules (2), the prescribed amount of cross-linked sodium carboxymethyl cellulose, and colloidal silica in a mixer and mix for 10 minutes to obtain dry granules (3). 7. Prepare a 6% (v / w) solution of coating material (Eudragit L100-55: HPMCP HP-50 = 1:1 (w / w)) with 75% ethanol and apply it to the dry particles (3) by fluidized bed bottom spray coating. Control the air inlet temperature at 55℃, the spraying speed at 15mL / min, the atomization pressure at 0.4 mPa, the pot rotation speed at 25 rpm, and the target coating weight gain at 5% to obtain wet coated particles (1). 8. Dry the wet-coated granules (1) in a fluidized bed at 55℃. The inlet air temperature is set to 55℃ and the fan frequency is 10~35Hz. After drying for 1 hour, take a sample and test the moisture content with a moisture analyzer. Stop drying when the moisture content is <2%, and then obtain enrofloxacin coated granules.

[0092] Comparative Example 1 This comparative example uses the formulation and preparation method described in Chinese Invention Patent CN115737593A to prepare an enrofloxacin taste-masking microcapsule. Specifically, by weight, the enrofloxacin taste-masking microcapsule is made from the following raw materials: 20g enrofloxacin, 6g nicotinamide, 0.25g polyvinylpyrrolidone K30, and 53.75g anhydrous glucose.

[0093] The preparation process of the above-mentioned enrofloxacin taste-masking microcapsules is as follows: 20g of enrofloxacin and 6g of nicotinamide are dissolved in 20g of the organic solvent methyl isobutyl ketone, and stirred at 1000rpm for 30min in a closed environment at 50℃ to prepare slurry A; 0.25g of polyvinylpyrrolidone K30 is dissolved in 50g of water to prepare slurry B, which serves as a binder; 53.75g of anhydrous glucose is used as a carrier, and fluidized bed granulation is carried out, with the air inlet volume of the fluidized bed controlled at 15m³. 3 / h, with an inlet air temperature of 45℃, two peristaltic pumps were used to spray slurry A and slurry B into a fluidized bed granulator for granulation, and the speed of the two peristaltic pumps was controlled at 5 rpm; after granulation, the granulation was carried out at 50℃ for 10 min, and the weight loss was less than 1%, resulting in enrofloxacin taste-masked microcapsules.

[0094] Comparative Example 2 This comparative example uses the formulation and preparation method described in Chinese Invention Patent CN103239422A to prepare an odorless coated enrofloxacin formulation. Specifically, the odorless coated enrofloxacin formulation, by weight, is made from the following raw materials: 8 kg of enrofloxacin, 0.05 kg of polyacrylic acid resin type II, 1.95 kg of polyethylene glycol, 60 kg of stearic acid, 30 kg of β-cyclodextrin, 55 kg of water, and 40 kg of anhydrous ethanol.

[0095] The preparation process of the above-mentioned odorless coated enrofloxacin formulation is as follows: β-cyclodextrin and water are mixed and stirred until homogeneous. Enrofloxacin and polyethylene glycol are added, and the mixture is stirred in a ball mill for 12 hours to fully encapsulate the enrofloxacin, thus obtaining the enrofloxacin inclusion complex. The obtained inclusion complex is dried at 65°C, pulverized, and passed through an 80-mesh sieve. Stearic acid is added to a reaction vessel and heated until it becomes a transparent liquid. The pulverized enrofloxacin inclusion complex is then added, stirred, mixed, sprayed, and freeze-dried to obtain microcapsule particles of about 20 mesh. Polyacrylic acid type II resin is dissolved in anhydrous ethanol, and the enrofloxacin microcapsule particles are placed in a cyclone fluidized bed for bottom spray coating to obtain the odorless coated enrofloxacin formulation.

[0096] Effect Example 1. Enrofloxacin content determination The enrofloxacin content determination of the enrofloxacin products of Examples 1-4 and Comparative Examples 1-2 was carried out using the following specific procedures: Take appropriate amounts of enrofloxacin products from Examples 1-4 and Comparative Examples 1-2, grind them finely, accurately weigh an appropriate amount (approximately equivalent to 25 mg of enrofloxacin), place it in a 100 mL volumetric flask, add 70 mL of mobile phase, sonicate for 15 min, cool, dilute to the mark with mobile phase, shake well, and filter. Accurately measure 5 mL of the filtrate, place it in a 25 mL volumetric flask, dilute to the mark with mobile phase, and shake well. Accurately measure 10 mL, and determine the content according to the method under the Enrofloxacin section of the 2020 edition of the Chinese Veterinary Pharmacopoeia. The content should be 90.0%~110.0% of the labeled amount.

[0097] Chromatographic conditions: Column: ZOBAX Eclipse XDB-C18, 250 mm × 4.6 mm, 5 μm; Mobile phase: 0.025 mol / L phosphoric acid solution (adjusted to pH 3.0 with triethylamine): acetonitrile = 83:17 (v / v); Column temperature: 30℃; Flow rate: 1.0 mL / min; Injection volume: 20 μL; Detection wavelength: 278 nm.

[0098] The results are shown in Table 1. The enrofloxacin content in the enrofloxacin products of Examples 1-4 and Comparative Examples 1-2 were 95.62%, 93.77%, 100.21%, 96.18%, 98.36%, and 103.52% of the labeled amount, respectively, all within the range of 90.0%-110.0%, which meets the standard.

[0099] Table 1. Results of Enrofloxacin Particle Content Determination

[0100] 2. Particle size analysis of enrofloxacin particles Weigh approximately 50 g of the enrofloxacin coated granules from Examples 1-4, the enrofloxacin taste-masked microcapsules from Comparative Example 1, and the tasteless coated enrofloxacin preparation from Comparative Example 2. Pass them through 20-mesh, 30-mesh, 40-mesh, 60-mesh, and 80-mesh sieves in sequence. Perform manual sieving according to Method II in Appendix 0982 of the Chinese Veterinary Pharmacopoeia (2020). Take the granules and powder that pass through the sieves, weigh them, and calculate the proportion of the granules to the total granule weight.

[0101] The results are as follows Figure 1 As shown. The enrofloxacin-coated granules of Examples 1-4, the enrofloxacin-masked microcapsules of Comparative Example 1, and the odorless enrofloxacin preparation of Comparative Example 2 failed to pass through sieve No. 1 (10 mesh), and the total percentages that passed through sieve No. 5 (80 mesh) were 8.36%, 15.18%, 3.69%, 4.52%, 5.53%, and 5.27%, respectively. Except for the enrofloxacin-coated granules of Example 2, which exceeded 15%, the granules of the other groups were all below 15%, which meets the requirements of the 2020 edition of the Chinese Veterinary Pharmacopoeia. Therefore, the enrofloxacin-coated granules of Example 2 were excluded, and further investigation will continue.

[0102] 3. Determination of the dissolution rate of enrofloxacin granules Dissolution tests were performed on the enrofloxacin coated granules of Examples 1, 3, and 4, the enrofloxacin taste-masked microcapsules of Comparative Example 1, and the tasteless coated enrofloxacin formulation of Comparative Example 2. The specific procedures are as follows: Chromatographic conditions: Mobile phase: 0.025 mol / L phosphoric acid solution (adjusted to pH 3.0 with triethylamine) - acetonitrile (83 / 17, v / v); UV detection wavelength: 278 nm; Column temperature: 30℃; Flow rate: 1.0 mL / min; Injection volume: 10 µL.

[0103] The dissolution test was performed according to Method II (paddle method) of the Dissolution Determination Method in the 2020 edition of the Chinese Veterinary Pharmacopoeia. 900 mL of dissolution medium (pH 1.2 / pH 4.3 / pH 6.8) was added to a dissolution vessel and heated to 37 ± 0.5 °C. An appropriate amount of enrofloxacin product was accurately weighed onto a weighing paper and quickly added to the dissolution vessel. The test was conducted with a paddle rotation speed of 75 rpm. Based on the retention time of food in the pig's gastrointestinal tract and pharmacopoeia requirements, the sampling times were set as follows: For pH 1.2 medium (purified water adjusted to pH 1.2 with 0.1 mol / L HCl solution), samples were taken at 0.5 h, 1 h, 1.5 h, 2 h, and 3 h; for pH 4.3 medium (pH 4.3 acetate-potassium acetate buffer), samples were taken at 0.5 h, 1 h, 2 h, 3 h, 4 h, and 6 h; and for pH 6.8 medium (pH 6.8 phosphate buffer solution), samples were taken at 0.5 h, 1 h, 1.5 h, and 2 h. The sampling volume was 5 mL. After sampling, an equal volume of dissolution medium was added to the dissolution system to maintain a constant dissolution rate. Samples were filtered through a 0.22 μm polytetrafluoroethylene microporous membrane and analyzed under the above chromatographic conditions. A standard curve was also prepared for quantification. The cumulative release rate in vitro was calculated using the formula below.

[0104]

[0105] In the formula: Qn represents the cumulative release percentage at time point n; Cn represents the drug concentration (μg / mL) in the sample taken at time point n; V represents the total volume of the medium in the dissolution vessel (mL); Ci represents the concentration (μg / mL) of the sample taken at time point i; Vi represents the sampling volume (mL) at time point i; m represents the mass of the drug used in the dissolution test; and ω represents the mass fraction of the drug loading in the test drug.

[0106] Three 850 mg portions of each of the three enrofloxacin-coated granules from Examples 1, 3, and 4 were accurately weighed and tested according to the dissolution test method described above. The obtained samples were filtered through a 0.22 μm polytetrafluoroethylene microporous membrane and injected for detection under the chromatographic conditions described above. A matching standard curve with gradient dilutions in the same medium was used for quantitative analysis. The peak areas were recorded, cumulative dissolution was calculated, and dissolution curves were plotted. The results are as follows: Figure 2 As shown.

[0107] Experimental Results: At pH 1.2, the dissolution rates of enrofloxacin-coated granules from Examples 1, 3, and 4, and the tasteless enrofloxacin preparation from Comparative Example 2, were all around 1%–3%, indicating almost no dissolution. In contrast, Comparative Example 1 showed approximately 63% dissolution after 3 hours, presumably due to the lack of coating causing the enrofloxacin in Comparative Example 1 to release in the simulated gastric environment, potentially leading to gastric irritation. At pH 4.3, the cumulative dissolution rates of enrofloxacin-coated granules from Examples 1, 3, and 4, the taste-masked enrofloxacin microcapsules of Comparative Example 1, and the taste-coated enrofloxacin preparation of Comparative Example 2 after 6 hours were approximately 17%, 28%, 43%, 98%, and 14%, respectively, indicating that the dissolution rate was significantly higher in the simulated gastric environment. In a simulated proximal duodenal environment, Comparative Example 1 showed the highest dissolution rate among the groups, followed by Example 4. At pH 6.8, the cumulative dissolution rates of enrofloxacin-coated granules from Examples 1, 3, and 4, the enrofloxacin-masked microcapsules of Comparative Example 1, and the flavor-coated enrofloxacin formulation of Comparative Example 2 at 2 hours were approximately 100%, 100%, 100%, 97%, and 76%, respectively. Examples 1, 3, and 4 all rapidly dissolved and released completely at 1 hour, with cumulative dissolution rates of approximately 85%, 81%, and 92% at 0.5 hours, respectively. This indicates that in a simulated jejunal environment, the dissolution rate of enrofloxacin-coated granules in Example 4 was the highest among the groups.

[0108] In summary, considering the goals of reducing gastric irritation and accelerating release and absorption in the proximal small intestine, the enrofloxacin-coated granules of Example 4 are the optimal formulation, denoted as pH-responsive enrofloxacin granules A.

[0109] 4. Examination of the appearance characteristics of enrofloxacin granules Take 2g each of pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Example 4), commercially available enrofloxacin granules B (Company A, content 10%, production batch number: 20230503), and commercially available enrofloxacin granules C (Company B, content 10%, production batch number: 23052501), place them on smooth paper, and spread them out in a single layer for about 5cm. 2 Flatten its surface and observe it in a bright place. It should be dry, with uniform granules and consistent color, and free from moisture absorption, softening, clumping, deliquescence, or other phenomena. Refer to Appendix 17 of the "General Rules for Granule Preparations" in the "Veterinary Pharmacopoeia of the People's Republic of China 2020 Edition - Chemical Drugs" to judge its appearance.

[0110] The results are as follows Figure 3 As shown, pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C are all off-white or light yellow granules. The granules are uniform in size and color, and there are no signs of moisture absorption, softening, clumping, or deliquescence, which meets the requirements of the 2020 edition of the Chinese Veterinary Pharmacopoeia.

[0111] 5. Particle size analysis of enrofloxacin particles Weigh approximately 50g each of pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C, and examine their particle size using the methods described in section 2.

[0112] The results are as follows Figure 4 As shown, the total percentages of pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C that could not pass through sieve No. 1 (10 mesh) and could pass through sieve No. 5 (80 mesh) were 8.5%, 1.4%, and 2.7%, respectively, all below 15%, which meets the requirements of the 2020 edition of the Chinese Veterinary Pharmacopoeia.

[0113] 6. Dissolution test of enrofloxacin granules The dissolution rate of pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C was investigated using the following specific method: Three 850 mg portions of each of the three types of 10% enrofloxacin granules (A, B, and C) were accurately weighed, and the dissolution rate was tested according to the method described in section 3. The results are as follows Figure 5 As shown, pH-responsive enrofloxacin granules A showed a cumulative dissolution of approximately 1.2% in pH 1.2 medium after 3 hours, approximately 40% in pH 4.3 medium after 6 hours, and approximately 100% in pH 6.8 medium after 2 hours. This indicates that pH-responsive enrofloxacin granules A are almost insoluble in the gastric pH environment, but begin to dissolve upon reaching the proximal small intestine pH environment, with the fastest release rate in the proximal jejunum pH environment, thus avoiding irritation to the stomach. Commercially available enrofloxacin granules B, on the other hand, showed dissolution at pH 4.3... The cumulative dissolution rate was lowest in pH 1.2 medium, with approximately 10% of the drug released cumulatively in 3 hours, indicating that particle B was difficult to dissolve in a simulated gastrointestinal environment. Commercially available enrofloxacin particles C showed a cumulative dissolution rate of approximately 95% in pH 1.2 medium after 3 hours, approximately 100% in pH 4.3 medium after 6 hours, and approximately 58% in pH 6.8 medium after 2 hours, indicating that commercially available enrofloxacin particles C dissolved more quickly in a simulated gastric and intestinal environment and had a poorer ability to avoid gastric irritation.

[0114] Therefore, it can be seen that the pH-responsive enrofloxacin granules A (i.e., the enrofloxacin coated granules of Example 4) provided by the present invention do not release in the gastric pH environment, but can release rapidly in the near-small intestinal pH environment, thus having pH-responsive capability, reducing the gastric irritation of enrofloxacin and ensuring that enrofloxacin is absorbed at the optimal site.

[0115] Application Example 1: Palatability Test of Enrofloxacin Granules This application example is used to examine the palatability of the enrofloxacin-coated granules from Example 4. The specific method is as follows: Experimental grouping: Pigs were randomly divided into groups A, B, C, and D. Each group was further divided into three gradient groups (low, medium, and high) according to the concentration of the mixed feed, for a total of 12 groups, with 13-16 pigs in each group. A blank control group was also set up (i.e., fed feed without any enrofloxacin granules or control drug). Among them, groups A, B, C, and D corresponded to pH-responsive enrofloxacin granules A (i.e., enrofloxacin coated granules from Example 4), commercially available enrofloxacin granules B, commercially available enrofloxacin granules C, and enrofloxacin raw material D (control group), respectively.

[0116] Experimental protocol: pH-responsive enrofloxacin granules A (i.e., the enrofloxacin-coated granules of Example 4), commercially available enrofloxacin granules B, commercially available enrofloxacin granules C, and enrofloxacin raw material D were administered to pigs at concentrations of 5 g / kg, 10 g / kg, and 20 g / kg of feed weight, respectively, mixed with feed. A one-bowl test method was used, employing a single food sample to assess the amount consumed and evaluate the inherent palatability of the food. A double crossover design was used to test the palatability of enrofloxacin; piglets in the same group underwent two tests with the same concentration of different test samples, and the average of the two data points was calculated to eliminate differences in feed intake between different groups.

[0117] Evaluation indicators: (1) Measure the weight of feed consumed by each group of pigs per meal in advance as the basis for guiding the experiment; (2) Count the feeding time, with 15 minutes as the feeding basis, and count the amount of leftover feed; (3) Count the total amount of feed per meal, the amount of leftover feed and the number of pigs in the experimental group, and calculate the feed intake rate and average feed intake. The formulas are as follows: Average feed intake rate = (total feed - amount of leftover feed) / total feed × 100%; Average feed intake = (total feed - amount of leftover feed) / number of pigs in the experimental group.

[0118] The results are as follows Figure 6 As shown, pH-responsive enrofloxacin granules A, B, and C all exhibited significant differences compared to the control drug D (enrofloxacin raw material) at all concentrations. This indicates that pH-responsive enrofloxacin granules A, B, and C can all improve the palatability of enrofloxacin. At feeding concentrations of 5, 10, and 20 g / kg, only pH-responsive enrofloxacin granules A showed no significant difference in average feed intake and average feed intake rate compared to the control, indicating that pH-responsive enrofloxacin granules A does not affect feed intake and feed intake rate in pig herds.

[0119] Application Example 2 This application example is used to investigate the pharmacokinetic study of enrofloxacin granules in pigs. The specific method is as follows: Experimental grouping: Eighteen pigs were randomly divided into three groups, A, B and C (corresponding to pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B and commercially available enrofloxacin granules C, respectively), with 6 pigs in each group. Each pig was administered the drug by gavage at a dose of 7.5 mg / kg (calculated as enrofloxacin).

[0120] Experimental animals: Eighteen healthy three-way crossbred pigs, 30-40 days old, weighing approximately 10 kg ± 2 kg, were fed according to standard feeding practices before the experiment, using a complete diet (excluding antibiotics). They were observed clinically for one week and showed good health. They were fasted for 12 hours before administration of the drug, and resumed normal eating 3-4 hours after gavage.

[0121] Plasma sample collection and processing: The patient was restrained in a supine position. Blood was collected from the anterior vena cava, approximately 5 mL each time. Blank plasma was collected before drug administration. Blood samples were collected at 15, 30, and 45 min and 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, and 48 h after drug administration. Immediately after collection, the samples were placed in 0.5% heparin sodium anticoagulant tubes and centrifuged at 3000 rpm for 10 min to separate the plasma. The plasma samples were then stored at -20℃. The plasma samples were thawed and well mixed. 0.5 mL was accurately pipetted into a 2 mL centrifuge tube, 1 mL of acetonitrile was added, and the mixture was vortexed. The mixture was centrifuged at 12000 rpm at 4℃ for 10 min. The supernatant was collected, filtered through a 0.22 μm microporous membrane, and analyzed by HPLC. Pharmacokinetic parameters were calculated, and drug-time curves were plotted.

[0122] Plasma sample analysis conditions: Chromatographic conditions: Column: ZOBAX Eclipse XDB-C18, 250 mm × 4.6 mm, 5 μm; Mobile phase: 0.025 mol / L phosphoric acid solution (adjusted to pH 3.0 with triethylamine), acetonitrile (83:17); Column temperature: 30 ℃; Flow rate: 1.0 mL / min; Injection volume: 20 μL; Detection wavelength: 278 nm.

[0123] The results are as follows Figure 7 As shown, the peak concentrations of pH-responsive enrofloxacin granules A and commercially available enrofloxacin granules C were 1.21 μg / mL and 1.65 μg / mL, respectively, which were 3.36 times and 4.58 times that of commercially available enrofloxacin granules B. Simultaneously, the areas under the pharmacokinetic curves (AUCs) of pH-responsive enrofloxacin granules A and commercially available enrofloxacin granules C were 4.61 times and 4.08 times that of commercially available enrofloxacin granules B, respectively, indicating a CUC size greater than B. This demonstrates that the pH-responsive enrofloxacin granules A provided by this invention significantly improves the oral bioavailability of enrofloxacin, achieving an effective therapeutic concentration with a dosing interval of every 24 hours, effectively reducing the frequency of administration and lowering treatment costs.

[0124] Application Example 3 This application example uses the enrofloxacin-coated granules from Example 4 in a clinical setting to investigate their efficacy in treating respiratory diseases. The specific method is as follows: Case details: On October 28th, a batch of 1150 weaned piglets was purchased. After the piglets arrived, tests for viral antigens such as ASFV, PPRSV, PCV, CSFV, and PRV were all negative, and the overall health of the pig herd was good. One week after they were raised, the pigs began to show respiratory diseases, mainly manifested as coughing and wheezing. Around November 20th, a large-scale outbreak of respiratory disease occurred at the farm, affecting about 10% of the pigs, and 8 pigs died during this period.

[0125] Disease diagnosis: Lung samples were collected from dead pigs and tested using qPCR kits (the kits for Bordetella bronchiseptica, Haemophilus parasuis, and Actinobacillus pleuropneumoniae were purchased from Hangzhou Geju Medical, catalog numbers GM3090, GM3078, and GM3091 respectively; the kit for Pasteurella multocida was purchased from Shanghai Xuanya Biotechnology, catalog number XY-PCR4524).

[0126] Treatment Plan: An enrofloxacin granule treatment trial was conducted in three pig houses with severe respiratory infections. House 1 had 460 pigs, with 43 affected (9.35%); House 2 had 448 pigs, with 39 affected (8.70%); and House 3 had 453 pigs, with 40 affected (8.83%). Houses 1, 2, and 3 were treated with pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C, respectively, mixed into feed at a dosage of 7.5 mg / kg body weight (calculated as enrofloxacin). The pigs were fed twice daily, once in the morning and once in the afternoon. Daily feed intake was recorded, and the daily number of affected pigs and the incidence rate were calculated.

[0127] The results are as follows Figure 8 As shown, qPCR results analysis revealed that *Bordetella bronchiseptica*... fla Genes, Haemophilus parasuis ompP2 Genes, Actinobacillus pleuropneumoniae apxIVAThe genes showed significant differences compared to the control group, and the diagnosis was respiratory disease caused by mixed bacterial infection. Feed intake of pigs fed with pH-responsive enrofloxacin granules A, commercially available enrofloxacin granules B, and commercially available enrofloxacin granules C mixed with feed steadily increased over 9 days. The decrease in feed intake on day 5 was due to feed restriction following vaccination; no drug-induced decrease in feed intake was observed throughout the entire treatment period. From day 1 to day 10 of the experiment, the number of cured pigs and the cure rate in the pH-responsive enrofloxacin granules A group, commercially available enrofloxacin granules B group, and commercially available enrofloxacin granules C group were 33 pigs and 76.74%, 26 pigs and 66.67%, and 26 pigs and 65.00%, respectively. No new cases were observed in the pH-responsive enrofloxacin granules A group during treatment, and the symptoms of previously untreated pigs also improved; its number of cured pigs and cure rate were the highest among the groups. This indicates that the use of enrofloxacin granules at the recommended dosage will not significantly affect the normal feed intake of pigs, and that pH-responsive enrofloxacin granule A is significantly more effective in treating respiratory diseases than commercially available enrofloxacin granules B and C.

[0128] In summary, the pH-responsive enrofloxacin granules provided by this invention effectively mask the bitter taste of the drug, reduce gastric irritation, decrease the frequency of administration, and prolong the duration of effective blood drug concentration. Furthermore, the pH-responsive enrofloxacin granules exhibit good therapeutic effects on porcine respiratory diseases.

[0129] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An enrofloxacin-coated granule, made from the following raw materials: enrofloxacin, filler, binder, disintegrant, glidant and coating material.

2. The enrofloxacin-coated granules according to claim 1, characterized in that, The filler includes at least one of glucose, lactose, sucrose, microcrystalline cellulose, starch, arabinose, trehalose, ribose, raffinose, isomaltol, lactitol, maltose, mannitol, and sorbitol; And / or, the adhesive comprises at least one of polyvinylpyrrolidone, polyethylene glycol, dextrin, gelatin, polyvinylpyrrolidone, methylcellulose, ethylcellulose and starch.

3. The enrofloxacin-coated granules according to claim 1, characterized in that, The disintegrant includes at least one of croscarmellose sodium, sodium carboxymethyl starch, sodium carboxymethyl cellulose, and hydroxypropyl methylcellulose; And / or, the flow aid includes at least one of silica, magnesium stearate, calcium stearate, and talc.

4. The enrofloxacin-coated granules according to claim 1, characterized in that, The coating material includes at least one of ethyl cellulose, cellulose acetate, hydroxypropyl methylcellulose phthalate, polyvinylpyrrolidone, acrylic resin, polyacrylic acid resin, and cyclodextrin.

5. The enrofloxacin-coated granules according to any one of claims 1 to 4, characterized in that, The raw materials comprise 1 to 30 parts by weight of enrofloxacin; And / or, by weight, the raw material includes 40 to 90 parts of filler; And / or, by weight, the raw material includes 1 to 10 parts of binder; And / or, by weight, the raw material includes 1 to 15 parts of disintegrant; And / or, by weight, the raw material includes 0.1 to 2 parts of a flow aid; And / or, by weight, the raw material includes 1 to 10 parts of coating material.

6. A method for preparing enrofloxacin-coated granules according to any one of claims 1 to 5, comprising the following steps: Enrofloxacin, filler, and partial disintegrant are mixed to obtain a mixture; The solution containing the binder is mixed with the mixture and granulated to obtain granules (1). Particles (1) are mixed with the remaining disintegrant and glidant to obtain particles (2); The particles (2) were coated with a coating material to obtain enrofloxacin coated particles.

7. The preparation method according to claim 6, characterized in that, Before being mixed with disintegrants and gliding agents, the particles (1) are dried and sieved.

8. The preparation method according to claim 6, characterized in that, The coating process includes the following steps: using a solution containing coating material to perform bottom spray coating on particles (2) in a fluidized bed, with a spraying speed of 5~30mL / min and an atomization pressure of 0.1~1mPa.

9. The use of enrofloxacin-coated granules according to any one of claims 1 to 5 in the preparation of the product; Preferably, the product includes at least one of a drug, feed, and feed additive.

10. A product comprising enrofloxacin coated granules as described in any one of claims 1 to 5.

Images