Gastrointestinal effects of sorbitol as an additive in liquid medications

Certain sugar alcohols, notably sorbitol, are widely used as a vehicle for drugs in liquid oral dosage forms. Gastrointestinal side effects due to osmotically active excipients have been described, but remain an underappreciated cause of diarrhea. Quantitating amounts of sorbitol is difficult due to a lack of compendial listings of such information. A computer search of Physicians' Desk Reference monographs was conducted to identify products that listed or potentially contained sorbitol as an inert ingredient. Standard form letters and telephone calls were used to collect information on the sorbitol content of products identified. Data were compiled for 142 products, and each value was converted to mg/mL as crystalline sorbitol. Some difficulty occurred obtaining requested information from some manufacturers in their effort to maintain product formulation confidentiality. Pharmaceutical manufacturers should recognize that technically inert ingredients are not necessarily pharmacologically inactive. Manufacturers should therefore comply with requests for, and more openly publish, quantitative information regarding such ingredients, to facilitate the assessment and treatment of patient symptoms.