Single and repeated dose kinetics of the hypnotic agent loprazolam in healthy volunteers

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Abstract
The pharmacokinetics of loprazolam have been studied in eight healthy male volunteers after single and repeated 2 mg oral doses taken at night, for eight nights. The absorption and disposition of unchanged drug (HPLC-GC assay) and receptor active benzodiazepine-type materials (radioreceptor assay) were examined after the first and eighth dose. Maximum levels of approximately 10 ng ml−1 (range 3.6 to 15.5 ng ml−1) were reached within about 2.5 h after dosing. The post-peak levels declined in a single exponential fashion with an overall mean±SD half-life of 7.06±1.98 h and total areas under the curve ranging from 35.9 to 189.0 ng ml−1 h. There were no statistical differences between the values for the first and eighth doses. There was no evidence to suggest that significant accumulation of parent drug or receptor active benzodiazepine-type materials had occurred, and it is concluded that the kinetics of loprazolam would allow repeated daily doses of 2 mg.