Elimination kinetics of desmethyldiazepam in two young and two elderlysubjects
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Pinazepam (P) (10 mg) was orally administered to two young (22–23 years) and two elderly (74–80 years) healthy volunteers. Also, desmethyldiazepam (DD) (10 mg) was orally administered to the same young volunteers on a separate occasion. P was almost completely converted into DD 24 h after administration. Plasma levels of DD were measured in all subjects. In all cases, the DD concentration-time curve showed a biphasic decay (a first slow decay was followed by a fast one) which closely fitted by a Michaelis-Menten equation. Vmax and km constant were computed for all subjects.
The kinetic analysis relative to the young subjects showed that T 1/2 of both the slow and fast decay as well as the area under the curve (AUC) were reduced when P was administered instead of DD. Comparison of DD kinetics between young and elderly subjects showed an increase of half-life in the elderly, while AUC was found unchanged.
Key wordsDesmethyldiazepam pinazepam pharmacokinetics aging
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