Effect of benzodiazepine hypnotics on all-night sleep EEG spectra

The effect of a single, oral bedtime dose of the benzodiazepine hypnotics flunitrazepam (FR; 2 mg), flurazepam (FR; 30 mg), and triazolam (TR; 0.5 mg) on the sleep stages and the sleep EEG was investigated in eight healthy, young subjects. In comparison to the placebo night, all drugs reduced the percentage of stage 1 and REM sleep, increased stage 2, and decreased the number of stage shifts. For FN and FR, some of these changes persisted in the postdrug night. All-night spectral analysis of the EEG showed a reduction of low-frequency activity (0.25-10.0 Hz) in stages 2, 3 + 4 and REM sleep, changes that persisted for all three drugs in the post-drug night. In the drug nights, activity in the spindle frequency range (11-14 Hz) was enhanced particularly in stage 2 and 3 + 4, activity in the high frequency range (17-25 Hz) particularly in REM sleep and stage 1. In the first third of the drug night, the depression of low-frequency activity in stage 2 was either absent (FR) or less prominent (FN, TR) than in the following part of the night. The results demonstrate that benzodiazepine hypnotics induce specific changes in the EEG spectra which reflect the immediate and residual drug effects more sensitively than conventional sleep scores.