Plasma levels and pharmacokinetics of single and multiple dose of tetrazepam in healthy volunteers.

The pharmacokinetics of tetrazepam (Myolastan, Musaril), were studied in 12 healthy volunteers. Tetrazepam was given orally as a single dose of 50 mg and repeated administration for 5 consecutive days of 50 mg at 12-h intervals, in tablet form. Tetrazepam was measured in plasma using a selective and sensitive GLC method. Tetrazepam is rapidly absorbed after oral administration with a peak plasma level of 0.49 +/- 0.10 mg/l at 0.94 +/- 0.47 h. The drug is widely distributed in the organism with an apparent volume of distribution of 6.7 +/- 2.1 l/kg. Tetrazepam is eliminated with a half-life of 22 +/- 4 h and can be classified as a benzodiazepine with medium half-life value. This medium half-life is the result of the high hepatic clearance of the drug in spite of its large distribution volume. Since in this study 6 male and 6 female volunteers were studied it was possible to compare the pharmacokinetic profile in the two groups. No significant differences were observed. No differences were observed between the pharmacokinetic values after a single dose or after repeated administration.