Psychomotor skills related to driving after intramuscular administration of diazepam and meperidine.

Psychomotor skills related to driving and the ability to discriminate the fusion of flickering light were measured in a double-blind cross-over fashion in 11 healthy volunteers before, and 1, 3, 5, and 7 hours after, intramuscular injection of saline solution, 10 mg diazepam, or 75 mg meperidine. The late effects of meperidine were tested in five other subjects 12 and 24 hours after the injection. The effects of diazepam were the most harmful to coordinative and reactive skills, which were significantly impaired for as long as 5 hours. Meperidine impaired reactive skills for as long as 3 hours and flicker-fusion discrimination and coordinative skills for as long as 12 hours. It is concluded that patients should not drive or operate machinery for at least 7 hours after receiving 10 mg diazepam intramuscularly and for 24 hours after receiving 75 mg meperidine intramuscularly.