PHARMACOKINETICS OF THIAMPHENICOL IN DOGS

Objective-To determine pharmacokinetic parameters of thiamphenicol (TA P) after IV and IM administration in dogs. Animals-6 healthy 2- to 3-y ear-old male Beagles. Procedure-In a crossover design study, 3 dogs we re given TAP IV, and 3 dogs were given TAP IM, each at a dosage of 40 mg/kg of body weight. Three weeks later, the same dogs were given a se cond dose by the opposite route. At preestablished times after TAP adm inistration, blood samples were collected through a catheter placed in the cephalic vein, and TAP concentration was determined by use of a h ighperformance liquid chromatography. Results-Kinetics of TAP administ ered IV were fitted by a biexponential equation with a rapid first dis position, phase followed by a slower disposition phase. Elimination ha lf-life was short (1.7 +/- 0.3 hours), volume of distribution at stead y state was 0.66 +/- 0.05 L/kg, and plasma clearance was 5.3 +/- 0.7 m l/min/kg. After IM administration, absorption was rapid. Peak plasma c oncentration (25.1 +/- 10.3 mu g/ml) was reached about 45 minutes afte r drug administration. The apparent elimination half-life after IM adm inistration (5.6 +/- 4.6 hours) was longer than that after IV administ ration probably because of the slow absorption rate from the muscle. M ean bioavailability after IM administration was 96 +/- 7%. Conclusion- The pharmacokinetic profile of TAP in dogs' suggests that it may be th erapeutically useful against susceptible microorganisms involved in th e most common infections in dogs, such as tracheobronchitis, enterocol itis, mastitis, and urinary tract infections.