Quazepam and flurazepam: differential pharmacokinetic and pharmacodynamic characteristics.

Quazepam and flurazepam share pharmacokinetic properties that result in prevention of early-morning insomnia, daytime rebound anxiety, and withdrawal rebound insomnia. Yet sleep laboratory and performance studies demonstrated that during a 1- to 4-week administration period quazepam had a low potential for causing daytime drowsiness or impairment. This profile may be related to several factors, such as differences in quazepam's metabolic pathways; plasma pharmacokinetics; rate of brain uptake, redistribution, and clearance; as well as differences in receptor binding and kinetics.