Paradoxical effects in sleep and performance of two doses of chlorpromazine.

Twenty-four subjects were given placebo, 25 mg, and 75 mg of chlorpromazine on three separate occasions. Twelve subjects were treated in the morning and tested for performance during the day. Twelve other subjects received the drug treatments in the evening. Both groups had their EEG stages of sleep recorded during the subsequent night. The low dose of drug shortened the REM/non-REM cycle length in comparison to the high dose, and placebo values were intermediate. In performance tests, visual integration time was impaired by the high dose of the drug. Logical reasoning was slowed by the high dose of the drug in comparison to the low dose, with placebo values intermediate between the two.