Pharmacokinetics of meloxicam in laying hens after single intravenous, oral, and intramuscular administration

The objective of this study was to determine the pharmacokinetics of meloxicam after a single intravenous (IV), intramuscular (IM), and oral (PO) dose at 1 mg/kg body weight in Jing Hong laying hens. Blood samples were collected at predetermined time points. Plasma meloxicam concentrations were determined using a validated high-performance liquid chromatography (HPLC) assay method and then subjected to a non-compartmental analysis. After IV administration, meloxicam had a mean (+/- SD) volume of distribution at steady-state (Vd(ss)) of 206.50 +/- 25.23 ml/kg, a terminal half-life (t(1/2 lambda)) of 5.45 +/- 0.53 h, and a total body clearance (Cl) of 26.48 +/- 4.13 ml/h/kg. After PO and IM administration, meloxicam was absorbed relatively rapidly: the peak concentrations (C(max)s) of 3.04 +/- 0.56 and 8.94 +/- 2.31 mu g/ml were observed at 3.08 and 0.80 h, respectively. After PO and IM administration, the absolute bioavailability (F) was determined as 70.13% and 125.50%, respectively. Assuming that hens shared the same analgesic threshold of meloxicam (0.5 mu g/ml) with humans, the plasma concentrations after three different routes (PO, IM, and IV) of administration were above this value for 16.7, 19.2, and 14.9 h, respectively.