Comparative pharmacokinetics of meloxicam in clinically normal horses and donkeys.
OBJECTIVE
To determine the disposition of a bolus of meloxicam (administered IV) in horses and donkeys (Equus asinus) and compare the relative pharmacokinetic variables between the species.


METHODS
5 clinically normal horses and 5 clinically normal donkeys.


METHODS
Blood samples were collected before and after IV administration of a bolus of meloxicam (0.6 mg/kg). Serum meloxicam concentrations were determined in triplicate via high-performance liquid chromatography. The serum concentration-time curve for each horse and donkey was analyzed separately to estimate standard noncompartmental pharmacokinetic variables.


RESULTS
In horses and donkeys, mean +/- SD area under the curve was 18.8 +/- 7.31 microg/mL/h and 4.6 +/- 2.55 microg/mL/h, respectively; mean residence time (MRT) was 9.6 +/- 9.24 hours and 0.6 +/- 0.36 hours, respectively. Total body clearance (CL(T)) was 34.7 +/- 9.21 mL/kg/h in horses and 187.9 +/- 147.26 mL/kg/h in donkeys. Volume of distribution at steady state (VD(SS)) was 270 +/- 160.5 mL/kg in horses and 93.2 +/- 33.74 mL/kg in donkeys. All values, except VD(SS), were significantly different between donkeys and horses.


CONCLUSIONS
The small VD(SS) of meloxicam in horses and donkeys (attributed to high protein binding) was similar to values determined for other nonsteroidal anti-inflammatory drugs. Compared with other species, horses had a much shorter MRT and greater CL(T) for meloxicam, indicating a rapid elimination of the drug from plasma; the even shorter MRT and greater CL(T) of meloxicam in donkeys, compared with horses, may make the use of the drug in this species impractical.
Sinclair
Melissa D
MD
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
Mealey
Katrina L
KL
Matthews
Nora S
NS
Peck
Ken E
KE
Taylor
Tex S
TS
Bennett
Brad S
BS
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D018397:Equidae / Q000097:blood*; D005260:Female; D006262:Health; D006736:Horses / Q000097:blood*; D008297:Male; D000077239:Meloxicam; D013045:Species Specificity; D013843:Thiazines / Q000097:blood / Q000493:pharmacokinetics*; D013844:Thiazoles / Q000097:blood / Q000493:pharmacokinetics*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D013843:Thiazines; D013844:Thiazoles; D000077239:Meloxicam