The absorption, blood concentrations and excretion of pentazocine after oral, intramuscular or rectal administration to man

Blood concentrations, urinary excretion rates and faecal excretion of unchanged drug were measured after oral, intramuscular or rectal administration of pentazocine; Significant inter-subject variation was observed. Blood concentration-time curves are related to urinary excretion rates. Relative physiological availabilities by each route were determined.