Sedative properties of doxepin in comparison with diazepam

Doxepin (Quitaxon^®) at doses of 25, 50, and 75 mg was compared with diazepam 7.5, 15, and 22.5 mg, using as variables the percentage lowering of Critical Flicker Fusion (CFF) and the self-estimated degree of drowsiness. Single doses were given, and repeated effect determinations were made over 6 h. Clear dose-effect relations could be demonstrated. The two drugs differed in speed and duration of action and in steepness of effect increase with dose. Although there were good correlations between CFF effect and subjective drowsiness, it seemed that the two methods interrelated somewhat differently in the different types of drug. CFF was a more stable and reliable method than the subjective estimation of drowsiness. However, when comparing drugs belonging to different classes, both methods preferably should be used together.