Single- and multiple-dose kinetics of estazolam, a triazolo benzodiazepine

The pharmacokinetic properties of estazolam, a triazolo benzodiazepine hypnotic agent, were assessed in a series of healthy volunteers following single and multiple doses. After single oral doses of 2--16 mg, peak plasma concentrations were reached within 6 h. Values of elimination half-life ranged from 8.3--31.2 h (mean 17.0 h) and did not vary significantly with dose. During 3 weeks of therapy, steady-state plasma concentrations increased approximately in proportion to increasing doses. and accumulation was essentially complete within 3 days of each dose change. The mean observed accumulation ratio was 1.84, which was slightly larger than the predicted ratio of 1.53. Exposure to multiple-dose estazolam therapy had no significant influence on the kinetics of a single dose of antipyrine, suggesting that estazolam neither stimulates nor inhibits enzyme activity in humans. Thus the accumulation and elimination kinetics of estazolam can be classified as intermediate to those of the short-acting (such as oxazepam) and the long-acting (such as diazepam) benzodiazepine derivatives.