Critical flicker fusion (CFF) test for sedative effect of antidepressants.

It is important to know in which direction and to what extent a drug affects cerebral arousal. Critical flicker fusion (CFF) is a most reliable method for measuring this particular quality of various drugs. A semi-automatic apparatus was used under standardized conditions, and double-blind technique was employed. Only acute experiments are described here. Dose-effect relationship can be demonstrated. The effect on cerebral arousal varies greatly from one antidepressant to another. Amitriptyline and doxepin were found to exert strong sedative effect, and amitriptyline-N-oxide an intermediate one, while imipramine and imipramine-N-oxide lacked this quality. Nomifensine in large doses has a significant stimulant action. Zimelidine in a low dose (75 mg) slightly, but significantly, lowered the CFF level, but at a dose of 150 mg no significant effect was obtained. At the doses 225 and 300 mg a slight increase was seen (about 2%). Various aspects of the findings are discussed in the paper.