Study on pharmacokinetics and bioequivalence of different preparations of azithromycin in

Objective: With LC/MS/MS for plasma concentration,the test formulation had a slow-release,burst effect,and the relative bioavailability compared with the reference formulation. Method: Nine Beagle dogs were randomized into group three, the test formulation,the reference formulation and azithromycin tablets were given to them.Azithromycin plasma was determined by LC-MS/MS.The separation was achieved on C₆-Phenyl column (100 nm×3.00 mm,Gemini 3 μm) with aqueous solution (0.1% formic acid)-methanol (30: 70) as mobile phase. Results: The correlation coefficients of the calibration curves were better than 0.9991(n=6),in the range of 0.05-10 μg·mL^-1 for azithromycin.The absolute recoveries were 80.0%-95.5%,the relative recoveries were 94.6%-101.2%.The intra-day and inter-day RSDs were less than 10.0%.The pharmacokinetic parameters of the Beagle dogs after given 2 g azithromycin A/B/C were as follows:T_max(3.17±2.70)h,(2.39±2.29)h and (0.50±0.22)h,C_max (3507.17±1811.27)μg·L^-1,(3582.53±949.30) μg·L^-1and (9668.10±3844.02) μg·L^-1,t_1/2 (56.01±23.07)h,(53.49±20.18)h and (44.29±12.07)h;AUC_0-t (67626.24±42712.70) μg·h·L^-1,(71198.01±19516.89) μg·h·L^-1 and (60141.05±18383.66) μg·h·L^-1;AUC_0-∞(86827.84±61174.14) μg·h·L^-1,(87291.59±27710.25) μg·h·L^-1 and (69769.39±23170.33) μg·h·L^-1.The relative bioavailability of azithromycin A to azithromycin B was (113.03±41.60)%. Conclusion: The method for the determination of azithromycin plasma concentration is sensitive and accurate;the test is bioequivalent with the reference formul Lation.

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