Pharmacokinetics and bioavailability of tildipirosin in rabbits following single-dose intravenous and intramuscular administration.

The objective of this study was to determine the pharmacokinetics of tildipirosin in rabbits after a single intravenous (i.v.) and intramuscular (i.m.) injection at a dose of 4 mg/kg. Twelve white New Zealand rabbits were assigned to a randomized, parallel trial design. Blood samples were collected prior to administration and up to 14 days postadministration. Plasma concentrations of tildipirosin were quantified using a validated ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. The pharmacokinetic parameters were calculated using a noncompartmental model in WinNonlin 5.2 software. Following i.v. and i.m. administration, the elimination half-life (T-1/2 lambda) was 81.17 +/- 9.28 and 96.68 +/- 15.37 hr, respectively, and the mean residence time (MRTlast) was 65.44 +/- 10.89 and 67.06 +/- 10.49 hr, respectively. After i.v. injection, the plasma clearance rate (Cl) and volume of distribution at steady state (V-dss) were 0.28 +/- 0.10 L kg(-1) h(-1)and 17.78 +/- 5.15 L/kg, respectively. The maximum plasma concentration (C-max) and time to reach maximum plasma concentration (T-max) after i.m. administration were 836.2 +/- 117.9 ng/ml and 0.33 +/- 0.17 hr, respectively. The absolute bioavailability of i.m. administration was 105.4%. Tildipirosin shows favorable pharmacokinetic characteristics in rabbits, with fast absorption, extensive distribution, and high bioavailability. These findings suggest that tildipirosin might be a potential drug for the prevention and treatment of respiratory diseases in rabbits.