Hypnotics and actual driving performance.

Several related studies of the residual effects of hypnotic drugs on actual driving performance have been conducted using a standard approach and the most recent is described in detail. In it, 12 female formerly diagnosed insomniacs and hypnotic users acted as subjects. They were treated in two separate series with placebo for 2 nights, then hypnotic medication for 8 nights followed by placebo again for 3 nights. In one series, the medication was nitrazepam (10 mg nocte) and in the other, temazepam (20 mg nocte). Eleven subjects completed both series in a double-blind, cross-over (with respect to drugs) design. Their driving performance was repeatedly tested on a 100 km primary highway circuit, in normal traffic, during both the morning and afternoon (10-11 hours and 16-17 hours after drug and placebo ingestion, respectively). Nitrazepam but not temazepam significantly impaired driving performance, the difference lasting throughout the active medication period. These results along with those obtained in the earlier studies are compared to show degrees of driving impairment which follow the use of various hypnotics.