Chronopharmacokinetics of pentazocine in the beagle dog.

Drug disposition of pentazocine was studied in the beagle dog upon i.v. administration of 30 mg in a crossover design with the variable being the time of administration. The pharmacokinetic parameters for the volume of distribution at steady state (V dss) and during the beta-phase (V d beta) and the biological half-life (t 1/2 beta) are statistically significant increased during the night, documenting circadian rhythm for the disposition of pentazocine. The total clearance (Cltot), however, remains unchanged.