Pharmacodynamic properties
Meloxicam is a Non-Steroidal Anti-Inflammatory Drug (NSAID) of the oxicam class which acts by inhibition of prostaglandin synthesis, thereby exerting anti-inflammatory, anti-exudative, analgesic and antipyretic effects. It reduces leukocyte infiltration into the inflamed tissue. To a minor extent it also inhibits collagen-induced thrombocyte aggregation. Meloxicam also has anti-endotoxic properties because it has been shown to inhibit production of thromboxane B2 induced by E. coli endotoxin administration in calves, lactating cows and pigs.
Pharmacokinetic properties
Absorption
After a single subcutaneous dose of 0.5mg meloxicam/kg, Cmax values of 2.1μg/ml and 2.7μg/ml were reached after 7.7 hours and 4 hours in young cattle and lactating cows, respectively. After two intramuscular doses of 0.4mg meloxicam/kg, a Cmax value of 1.9 μg/ml was reached after 1 hour in pigs.
Distribution
More than 98% of meloxicam is bound to plasma proteins. The highest meloxicam concentrations are to be found in liver and kidney. Comparatively low concentrations are detectable in skeletal muscle and fat.
Metabolism
Meloxicam is predominately found in plasma. In cattle, meloxicam is also a major excretion product in milk and bile where as urine contains only traces of the parent compound. In pigs, bile and urine contain only traces of the parent compound. Meloxicam is metabolised to an alcohol, an acid derivative and to several polar metabolites. All major metabolites have been shown to be pharmacologically inactive. The metabolism in horses has not been investigated.
Elimination
Meloxicam is eliminated with a half life of 26 hours and 17.5 hours after subcutaneous injection in young cattle and lactating cows, respectively. In pigs, after intramuscular injection, the mean plasma elimination half life is approximately 2.5 hours. In horses, after intravenous injection meloxicam is eliminated with a terminal half-life of 8.5 hours. Approximately 50% of the administered dose is eliminated via urine and the remainder via faeces.