Pharmacokinetic interactions of flunixin meglumine and enrofloxacin in dogs.
OBJECTIVE
To examine pharmacokinetic interactions of flunixin meglumine and enrofloxacin in dogs following simultaneously administered SC injections of these drugs.


METHODS
10 Beagles (4 males and 6 females).


METHODS
All dogs underwent the following 3 drug administration protocols with a 4-week washout period between treatments: flunixin administration alone (1 mg/kg, SC); simultaneous administration of flunixin (1 mg/kg, SC) and enrofloxacin (5 mg/kg, SC); and enrofloxacin administration alone (5 mg/kg, SC). Blood samples were collected from the cephalic vein at 0.5, 0.75, 1, 1.5, 2, 3, 5, 8, 12, and 24 hours following SC injections, and pharmacokinetic parameters of flunixin and enrofloxacin were calculated from plasma drug concentrations.


RESULTS
Significant increases in the area under the curve (32%) and in the elimination half-life (29%) and a significant decrease (23%) in the elimination rate constant from the central compartment of flunixin were found following coadministration with enrofloxacin, compared with administration of flunixin alone. A significant increase (50%) in the elimination half-life and a significant decrease (21%) in the maximum plasma drug concentration of enrofloxacin were found following coadministration with flunixin, compared with administration of enrofloxacin alone.


CONCLUSIONS
The observed decrease in drug clearances as a result of coadministration of flunixin and enrofloxacin indicates that these drugs interact during the elimination phase. Consequently, care should be taken during the concomitant use of flunixin and enrofloxacin in dogs to avoid adverse drug reactions.
Ogino
Tomoe
T
National Veterinary Assay Laboratory, 1-15-1 Tokura, Kokubunji, Tokyo 185-8511, Japan.
Mizuno
Yasuharu
Y
Ogata
Tomoko
T
Takahashi
Yoshiyuki
Y
D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood / Q000493:pharmacokinetics*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D003002:Clonixin / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D004285:Dogs / Q000378:metabolism*; D004347:Drug Interactions; D000077422:Enrofloxacin; D005260:Female; D024841:Fluoroquinolones / Q000097:blood / Q000493:pharmacokinetics*; D006207:Half-Life; D008297:Male
D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D024841:Fluoroquinolones; D000077422:Enrofloxacin; C014558:flunixin meglumine; D003002:Clonixin