Diphenhydramine and the calcium carbimide-ethanol reaction: a placebo-controlled clinical study.

The effect of diphenhydramine on the cyanamide-ethanol reaction was evaluated in a double-blind, controlled clinical study. Seven healthy subjects ingested 50 mg calcium carbimide at 4 hours and 100 mg diphenhydramine or placebo at 2 hours before a 0.2 gm/kg iv infusion of ethanol. Blood acetaldehyde and blood ethanol analyses were performed together with recordings of blood pressure, pulse rate, and flushing intensity during the hour after ethanol infusion. Diphenhydramine increased the mean ethanol AUC but did not influence blood acetaldehyde levels. Antihistamine reduced the flushing response by 40% and decreased the pulse rate from 40 minutes onward after ethanol infusion subsequent to calcium carbamide dosing. Blood pressure was not significantly influenced by ethanol at the calcium carbimide dose we used.