Pharmacokinetics of meloxicam in lactating goats ( Capra hircus ) and its quantification in milk after a single intravenous and intramuscular injection

Domestic goats, although present in large numbers worldwide, are still considered a minor species in Europe and the USA. Due to their minor status, new therapies directed to relieve pain is a neglected area of investigation. Unfortunately there is a lack of approved drugs for this species and many drugs are administered in an extra-label manner. Often no information on the safety profile for goats and for humans consuming their products is available. Meloxicam (MEL) is a potent anti-inflammatory drug characterized by a preferential COX-2 isoenzyme inhibition. The aim of this study was to determine the pharmacokinetics of MEL at the dose of 0.5 mg/kg in lactating goats after intravenous (IV) and intramuscular (IM) administration and to quantify its residues in milk. The analytical method was performed by the HPLC diode array detector. The IV and IM administrations of MEL in lactating goats showed suitable pharmacokinetic profiles for this animal species. The IM route showed a bioavailability of 105% and long half-life of elimination (10.82 h). The simulation of multiple daily IM injections provides a plasma concentration above the therapeutic concentrations determined for other species for the majority of 24 h. The high IM bioavailability, the long half-life of elimination and the mean plasma concentration at the steady state suggested that once a day administration might be sufficient. MEL residues were quantifiable in milk up to 48 h in IM group and 60 h in the IV group. This data seems to be in line with the milk depletion reported in cattle. Further studies are necessary to establish if the minimal effective concentration determined in other animal species can be applied to goats too.