Pharmacokinetics of doxycycline after a single intravenous, oral or intramuscular dose in Muscovy ducks (Cairina moschata)

The pharmacokinetics of doxycycline in ducks were investigated after a single intravenous (IV), intramuscular (IM) or oral (PO) dose at 20mg/kg body weight. The concentrations of doxycycline in plasma samples were assayed using a high performance liquid chromatography method, and pharmacokinetic parameters were calculated using a non-compartmental model. After IV administration, doxycycline had a mean (+/- SD) distribution volume (V-z) of 1761.9 +/- 328.5ml/kg and was slowly eliminated with a terminal half-life (t(1/2 lambda z)) of 21.21 +/- 1.47h and a total body clearance (Cl) of 57.51 +/- 9.50ml/h/kg. Following PO and IM administration, doxycycline was relatively slowly absorbed - the peak concentrations (C-max) were 17.57 +/- 4.66 mu g/ml at 2h and 25.01 +/- 4.18 mu g/ml at 1.5h, respectively. The absolute bioavailabilities (F) of doxycycline after PO and IM administration were 39.13% and 70.71%, respectively. The plasma profile of doxycycline exhibited favourable pharmacokinetics characteristics in Muscovy ducks, such as wide distribution, relatively slow absorption and slow elimination, though oral bioavailability was low.