[Effect of phenazepam on sleep cycles in rats]

It has been shown in experiments on rats that a single administration of phenazepam in doses of 0.5 and 2 mg/kg reduces the period of falling asleep and of being conscious, shortens the duration of the paradoxical sleep phase and increases the duration of slow-wave sleep thereby indicating the intensity of the drug hypnotic effect. Prolonged (10 days) administration of phenazepam does not induce tolerance. However, after the drug discontinuation there develops a withdrawal syndrome that is characterised by changes in the sleep structure.