Pharmacokinetics of the insulin-sensitizing agent troglitazone in cats

OBJECTIVE: To determine pharmacokinetics of troglitazone in healthy cats after i.v. and oral administration of a single dose of the drug. ANIMALS: 5 healthy ovariohysterectomized adult cats. PROCEDURE: Using a randomized crossover design, cats were given 5 mg of troglitazone/kg of body weight i.v. and 40 mg of troglitazone/kg orally. Blood and urine samples were collected after drug administration, and concentrations of troglitazone in plasma and urine were determined by use of high-performance liquid chromatography. RESULTS: Area-moment analysis was used to calculate pharmacokinetic variables. Terminal phase half-life was 1.1 +/- 0.1 hours. Steady-state volume of distribution was 0.23 +/- 0.15 L/kg. After i.v. administration, clearance was 0.33 +/- 0.04 L/h/kg. Drug was not detected in urine samples. Mean bioavailability of orally administered troglitazone was 6.9%. CONCLUSIONS AND CLINICAL RELEVANCE: The overall disposition of troglitazone in cats was similar to that reported in other species, including humans. Troglitazone has low and variable oral bioavailability. Clearance of the compound is moderate. Little if any unchanged troglitazone is excreted in urine; thus, metabolism and biliary excretion play predominant roles in elimination of the drug. On the basis of troglitazone pharmacokinetics in healthy cats, as well as on the basis of pharmacodynamics of the drug in humans and other animals, a regimen that uses a dosage of 20 to 40 mg/kg administered orally once or twice per day to cats will produce plasma concentrations of the insulin-sensitizing agent that have been documented to be effective in humans.