Pharmacokinetics and bioavailability of valnemulin in Muscovy ducks (Cairina moschata)

1. A pharmacokinetic study of valnemulin was conducted in healthy Muscovy ducks after intravenous (IV), intramuscular (IM) and oral administrations at a dose rate of 15 mg/kg body weight. 2. Drug concentrations in plasma were determined by high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetics parameters of valnemulin were analysed by compartmental analysis using the WinNonlin program. 3. After IV administration, valnemulin was widely distributed with a volume of distribution based on a terminal phase (V(z)) of 8·19 ± 3·07 l/kg, a mean elimination half-life (t(1/2Ke)) of 2·63 h, and a clearance (Cl) value of 5·56 ± 1·53 l/kg/h. Following intramuscular and oral administration, valnemulin was rapidly absorbed; the C(max) was 0·44 ± 0·13 and 0·12 ± 0·02 µg/ml (achieved at 0·28 and 1·80 h), the t(1/2Ke) was 3·17 ± 3·83 and 4·83 ± 1·81 h, and the absolute bioavailability (F) was 72% and 37%, respectively. 4. The plasma profile of valnemulin exhibited favourable pharmacokinetic characteristics in Muscovy ducks, such as wide distribution, and rapid absorption and elimination, though oral bioavailability was low.