Biliary excretion of [14C]temazepam and its metabolites in the rat

The excretion of temazepam and its N-desmethyl metabolite, oxazepam, and their respective O-conjugates was examined following a single intravenous dose of [14C]temazepam to two groups of bile fistula rats, with and without bile replenishment to the animals via duodenal cannulae. During an 8-hr collection period, the two groups produced virtually identical bile volumes, and there were no significant differences between them in the amount of total radioactivity, free temazepam, or the identified metabolites in the bile, as determined by TLC and liquid scintillation counting. Elimination of the radioactive dose was rapid during 0-8 hr, with a half-life of approximately 1 hr. Approximately 85-90% of the administered radioactivity was recovered in the bile: less than 1% as free temazepam, 3% as oxazepam, and approximately 10% as their O-conjugates.