Onset and duration of action of benzodiazepines as determined by inhibition of (3H)-flunitrazepam binding

The present study examine ex vivo percent inhibition of (3H)-flunitrazepam ((3H)-FNZ) binding to brain tissue homogenates obtained from rats or mice at various time intervals after intravenous administration of benzodiazepines. The peak effect of benzodiazepines was observed within 1–10 min, and their intensity and duration of action could be increased by raising the dose administered. The benzodiazepines were found to differ with respect to onset of peak effect, duration of maximum effect, total length of action, and brain half-life. The ex vivo determination of (3H)-FNZ binding is thought measure benzodiazepine-like activity produced by the parent compound and its active metabolites.