Pharmacokinetics
Oral administration of 15 to 45 mg temazepam in man resulted in rapid absorption with significant blood levels achieved in less than 30 minutes and peak levels at 2 to 3 hours. In a single and multiple dose absorption, distribution, metabolism, and excretion (ADME) study, using tritium (3H) labelled drug, temazepam was well absorbed and found to have minimal (8%) first pass drug metabolism. There were no active metabolites formed and the only significant metabolite present in blood was the O-conjugate. The unchanged drug was 96% bound to plasma proteins. The blood level decline of the parent drug was biphasic with the short half-life ranging from 0.4-0.6 hours and the terminal half-life from 3.5–18.4 hours (mean 8.8 hours), depending on the study population and method of determination.
Temazepam has very good bioavailability with almost 100% being absorbed from the gut. The drug is metabolized through conjugation and demethylation prior to excretion. Most of the drug is excreted in the urine, with about 20% appearing in the feces. The major metabolite was the O-conjugate of temazepam (90%); the O-conjugate of N-desmethyl temazepam was a minor metabolite (7%).
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