The separate effects of propantheline, atropine, and metoclopramide on ethanol absorption have been studied in man. Intravenous propantheline lowered blood ethanol levels after ingestion of a standard ethanol load. Oral propantheline, at dose levels currently recommended for therapeutic use, was without significant effect on ethanol tolerance, whereas the tolerance was reduced by oral atropine. Propantheline bromide tablets have been shown to undergo significant hydrolysis at alkaline pH in vitro. Metoclopramide, given intravenously and orally, significant elevated blood ethanol levels soon after ingestion of a standard ethanol load. It is suggested that when propantheline is selected as an anticholinergic for clinical use, there is need for greater awareness of the marked reduction in bioavailablity that results when the drug is administered at conventional therapeutic dosage by the oral as opposed to the intravenous route.