Biopharmaceutic influences on the anticholinergic effects of propantheline

With reduction of salivary flow rate as an index of anticholinergic response, 3 subjects manifested demonstrable effects shortly after ingestion of 15‐mg doses of propantheline in conventional tablets. Ingestion of this dose immediately after a standardized breakfast substantially reduced the anticholinergic effects. In 1 subject, a dose‐response relationship was noted after 15 mg and 30 mg doses under both fasting and fed conditions, but at each dose level the influence of food was clear. Administration of a 30‐mg dose of propantheline in a commercially available “prolonged‐acting” tablet induced little if any anticholinergic effects; in 2 subjects, marginal but fleeting indications of salivary suppression were noted about 4 hr after ingestion, while no effects were observed in the third subject (even after 2 “prolonged‐acting” tablets).