Comparative Evaluation of the Pharmacokinetics of Tylosin 50 and Tylanic 5% Medicinal Products and Statistical Substantiation of Their Bioequivalence

Using the microbiological agar diffusion method, the daily dynamics of tylosin antibiotic concentration in the blood serum of six cattle after a single intramuscular administration of injectable tylosin tartrate (Tylosin 50, investigational product) and tylosin base (Tylanic 5%, reference product) were evaluated. In contrast to Tylanic 5%, Tylosin 50 additionally contained ascorbic acid, sodium metabisulfite, and Trilon B. A sequential study design was used.

The calculated pharmacokinetic parameters demonstrated that Tylosin 50 penetrated the systemic circulation more actively than Tylanic 5%. Meanwhile, the differences in distribution volumes, elimination constants, and clearance values were not statistically significant. Thus, the antibiotic form in the preparation, the composition of excipients, and the acidity of the injection solution affected the absorption rate of the active substance but did not influence the distribution and elimination of the drug from the calves’ organism.

The two-sided 90% confidence interval for the ratios of Cmax and AUCt ranged from 80.00 to 125.00%, while for the ratios of Cmax/AUCt and Cmax/AUC∞ it ranged from 75 to 133%, which corresponds to the established bioequivalence acceptance criteria.

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