An analysis of the inter-subject variation in the metabolism of pentazocine

Significant inter-subject variation in the cumulative urinary excretion of pentazocine, following its oral administration, was observed. Individual variations in the rate of metabolic oxidation of pentazocine are responsible for the variations in the urinary excretion of pentazocine (24 h cumulative). Smoking did not affect the metabolism of the drug. Pharmacokinetic analysis of the urinary excretion rate of pentazocine, using an open three compartment model, indicated that the fractional metabolic clearance is correlated with the cumulative urinary excretion (24 h) of the drug under conditions of acidic urinary pH. A g.l.c. method for the determination of pentazocine in urine is described.