Abstract:A recently marketed prolonged‐release quinidine gluconate tablet was compared with the innovator's tablet in a single‐dose bioavailability study with 12 healthy male subjects. The extent of absorption of quinidine from the new marketed product was only 50 per cent that of the innovator's product. This finding, as well as projections of steady‐state plasma concentrations to be expected during multiple‐dose administration, indicated a bioequivalence problem with medically significant implications. The data obtained in this study resulted in a Class I recall of the less completely absorbed product by the U.S. Food and Drug Adminis