Disposition kinetics of tildipirosin in alpacas after parenteral administrations

Tildipirosin is a macrolide antibiotic marketed in veterinary medicine to treat respiratory infections in pigs and calves. There are no pharmacokinetics studies of tildipirosin after parenteral administration in alpacas which is an extremely decisive step for determining dosage regimen. Thus, the aim of the present study was to establish the disposition fate of tildipirosin following intravenous (IV), intramuscular (IM) and subcutaneous (SC) administrations in alpacas. A crossover study was used, and each alpaca received a single dose of tildipirosin by IV and IM or SC. All the routes of administration were adequately tolerated, and no adverse reactions was observed in any alpaca. Tildipirosin in alpacas reached peak concentrations (C_max = 0.68 µg/mL vs. 0.79 µg/mL) at 0.22 and 0.50 h (t_max) after IM and SC administration, respectively, with an absolute bioavailability of >100 % for both routes of administration. Steady-state volume of distribution and clearance were 6.02 ± 1.34 L/kg and 2.76 ± 0.28 L/h/kg, respectively. Tildipirosin presents a particular pharmacokinetic behaviour in alpacas, distinctive from other ruminant species, confirming the need to perform studies in the target species in order to promote rational dose regimens of this antimicrobial to maximize its efficacy, minimize its toxicity and avoid the emergence of resistant bacteria.