Pharmacokinetics of meloxicam in plasma and urine of horses.
OBJECTIVE
To determine pharmacokinetic parameters for meloxicam, a nonsteroidal anti-inflammatory drug, in horses.


METHODS
8 healthy horses.


METHODS
In the first phase of the study, horses were administered meloxicam once in accordance with a 2 x 2 crossover design (IV or PO drug administration; horses fed or not fed). The second phase used a multiple-dose regimen (daily oral administration of meloxicam for 14 days), with meloxicam administered at the recommended dosage (0.6 mg/kg). Plasma and urine concentrations of meloxicam were measured by use of validated methods with a limit of quantification of 10 ng/mL for plasma and 20 ng/mL for urine.


RESULTS
Plasma clearance was low (mean +/- SD; 34 +/- 0.5 mL/kg/h), steady-state volume of distribution was limited (0.12 +/- 0.018 L/kg), and terminal half-life was 8.54 +/- 3.02 hours. After oral administration, bioavailability was nearly total regardless of feeding status (98 +/- 12% in fed horses and 85 +/- 19% in nonfed horses). During once-daily administration for 14 days, we did not detect drug accumulation in the plasma. Meloxicam was eliminated via the urine with a urine-to-plasma concentration that ranged from 13 to 18. Concentrations were detected for a relatively short period (3 days) after administration of the final daily dose.


CONCLUSIONS
Results of this study support once-daily administration of meloxicam regardless of the feeding status of a horse and suggest a period of at least 3 days before urine concentrations of meloxicam reach concentrations that could be used in drug control programs.
Toutain
Pierre-Louis
PL
UMR 181 Physiopathologie et Toxicologie Expérimentales, INRA/ENVT, Ecole Nationale Vétérinaire de Toulouse, 23 Chemin des Capelles, 31076 Toulouse, France.
Reymond
Nadège
N
Laroute
Valérie
V
Garcia
Patrice
P
Popot
Marie-Agnès
MA
Bonnaire
Yves
Y
Hirsch
Alexandra
A
Narbe
Rüdiger
R
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine; D002851:Chromatography, High Pressure Liquid; D018592:Cross-Over Studies; D006736:Horses / Q000378:metabolism*; D013058:Mass Spectrometry; D000077239:Meloxicam; D013843:Thiazines / Q000097:blood* / Q000493:pharmacokinetics* / Q000652:urine*; D013844:Thiazoles / Q000097:blood* / Q000493:pharmacokinetics* / Q000652:urine*; D013997:Time Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013843:Thiazines; D013844:Thiazoles; D000077239:Meloxicam