| Tilmicosin is a novel macrolide antibiotic with a wide therapeutic uses against bacteria. It has a broad antibactertial spectrum,low drug resistance, minor toxicity and cross resistance. it has strong inhibitory effect against Grampositive and Gramnegtive bacteria,as well as Mycoplasma and Leptospira. Due to its special antibacterial potency and pharmacokinetic feature, Tilmicosin has been widely used in animal for preventive and therapeutic purposes. Tilmicosin causes no teratogenesis, mutagenesis, arcinogenesis and embryo poisonousness, which makes it safe enough to be widely used in veterinary clinic treatment. This antibiotic also known for its bitter taste and irritative odor. Animals exhibit bad compliance, unequable consumption or even no consumption to this antibiotic while it’s fed with food. All these negative factors combined with the unsafety of administration method restrict the clinic application to animals especially pigs. Thus the development of its new type of formula for gastrointestinal administration is critical to effective and safe usage on infected animals. Based on it this test carried out a series of research aiming at developing Tilmicosin enteric-coated pellets.The UV-spectrophotometric method was established to investige pellets drug release. The assaying wavelength was selected at 280nm and the resulting regression equation correlating between released drug concentration of Tilmicosin in 0.1 mol·L-acid solution and absorbency was:Y=0.023X+0.014, R2=0.9993. Within 9.5886μg·ml-1～47.943μg·ml-1, the drug concentration showed linear relationship with absorbency. In pH6.8 phosphate buffered saline solution, the corresponding regression equation was:Y=0.0244X+0.0019, R2=1 and the drug concentration showed linear relationship with absorbency while ranging from 9.6647μg·ml-1 to 48.3235μg·ml-1.Those demonstrated that the established UV method was simple and quick in operation, highly sensitive and could result in a relatively stable data, thus excellent for rapid analysis and assay in manufacture and suitable for quality control in manufacturing process. Then the High-performance liquid chromatography was applied to determine the concentration of Tilmicosin by Agilent TC-C18 chromatographic column (150×4.6mm). The used conditions were:The mobile phase used was mixture of acetonitrile, tetrahydrofuran and phosphate solution(containing 1 mol·L-1 Di-n-butylamine) with proportion of 130:55:25(V/V). The washing speed was 1.0ml·min-1; The UV detection wavelength was 280 nm and sample size was 20μl。The resulting regression equation was Y=21.174X+0.0499, R2=1, the drug concentration indicated a good linear relationship with absorbency within 0.5～20μg·ml-1. Another HPLC was established to assaying Tilmicosin concentration in plasm samples by Agilent TC-C18.The established conditions were; The mobile phase used was mixture of acetonitrile, tetrahydrofuran and phosphate solution(containing 1 mol·L-Di-n-butylamine) with proportion of 130:55.25:790 (V/V). the washing speed was 1.0ml·min-1; the column temperature was 30℃, the UV detection wavelength was 280 nm and sample size was 20μl。The resulting regression equation was Y=38781X--882.19, R2=0.9993 the drug concentration indicated a good linear relationship with absorbency within 0.05μg·ml-1～2μg·ml-1 and the minimal detectable concentration was 0.05μg·ml-1. The results showed the established HPLC methods were easy to operation and resulted in a high sensitivity, low minimal detectable concentration and stable data, thus suitable for rigorous analysis of formula and drug metabolism. It can met the requirement for quality control and metabolism research of Tilmicosin.In this experiment, Tilmicosin Pellet cores were prepared by extrusion-spheronization. Based on preliminary experiment, the production conditions were set as:0.6mm of extrusion aperture,40rpm of extrusion speed,650rpm of roll speed,2min of rolling time,25Hz of blast speed and 1g Silicon dioxide as lubricant before adding the materials. The pellets were dried at 60℃.With 24 mesh～40 mesh as qualified pellets, the proportion of starch to dextrin, the content of Corncob Powder, the variety and content of adhesives were assayed through single factor test for determination of pellet formula, with coefficient of recovery, bulk density, sphericity, friabibity, surface morphology and colligation score of pellets as indices. The resulting formula was as follow:proportion of starch to dextrin is 9:1, the content of Corncob Powder is 25% of total diluent, and 55ml of 3% HPMC water solution. A single factor test analyzed the technologic factors that affect the formation of pellets including extrusion speed, spheronization speed and time. The result showed the proper technologic parameters were:40rpm of extrusion speed,650rpm of rolling speed, and 2min of rolling time. Considering the interaction of each factor might affect the quality of pellet cores, an orthogonal test L9(33) was performed based on the previous single factor test and The influencing degree of each factor on the score was determined as follows:extrusion speed (A)>rolling time (B)>rolling speed(C), with the optimum combination A3B3C3, The optimum technologic conditions determined were:30 rpm the extrusion speed,700 rpm the spheronization speed and 2.5 min the spheronization time.The pellets were coated with acrylic resin using Centrifugal coating machine.The determined technologic parameters were:400g of feeding mass,250rpm of turnplate speed,25 Hz of blast speed,25℃～30℃of coating temperature,0.1 Mpa spray pressure and 5ml·min-1 liquid suppling speed. Besides,based on the release behavior, the effect of proportion of acrylic resinâ…¡andâ…¢,content of Plasticizer and Antistatic Agent SDS,the coating weight gain of on enteral pellets release were investigated to determine the formula. The resulting formula was:2:1 the proportion of acrylic resinâ…¡andâ…¢,30% the content of Plasticizer in total polymers,0.2% SDS content and 20% increase in coating weight. The stability test of Tilmicosin enteral pellets showed a gradual decrease of pellets content under intense light and high temperature, indicating the pellets should be stored in cool and dark place. The humidity test, short-time test and long-run test indicated none obvious change for pellets character, content, release degree in acid and alkaline solutions.For Pharmacokinetic study, the enteral pellets were applied to High-performance liquid chromatography to measure the Tilmicosin concentration in six weaned pigs.The Pharmacokinetic parameters were:T1/2=16.99h, Cmax=0.944μg·ml-1, Tmax=6.33h, AUC 0â†'24=13.947μg·ml-1·h, AUC 0â†'∞=16.1433μg·ml-1·h. The result showed that enteral pellets form of Tilmicosin presented a lagging peak time compared to the previous report of Tilmicosin, which accorded with the property of enteric-coated preparations. |
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