Pharmacokinetics of Pentazocine in Dogs under Halothane Anesthesia

The pharmacokinetics of pentazocine were studied in dogs under halothane anesthesia. Pentazocine was spectrofluorometically measured in plasma and cerebrospinal fluid (CFS) of dogs receiving 2.5, 5.0, 10.0 mg/kg doses intramuscularly. The concentration-time curves of pentazocine were describable in terms of a 2-compartment model, and the pharmacokinetic parameters were calculated accordingly. The half-life of the β-phase (elimination phase) was independent of the dose, while the area under the curves (AUC) were proportional to the dose levels. Pharmacokinetic parameters of pentazocine in unanesthetized dogs were also calculated and compared with those in anesthetized dogs. The half-life was approximately the same in both groups. It is concluded that halothane anesthesia does not significantly modify the half-life of pentazocine.