The Relationship Between Physiological Availability of Salicylates and Riboflavin and In Vitro Disintegration Time of Enteric Coated Tablets

Abstract

Studies were conducted to relate the in vitro disintegration time of enteric coated tablets with physiological availability of salicylates and riboflavin, as determined by the urinary excretion of these drugs by human subjects. In vitro disintegration times were determined by the procedure given in U. S. P. XV Second Supplement, modified by the use of sixty minutes time in simulated gastric juice. Rates of urinary excretion of the drugs were determined after dosing subjects with seven salicylate preparations and five riboflavin preparations. Two products were found which disintegrated after less than thirty minutes in simulated gastric juice, while a third product was extremely resistant to the simulated digestive juices, and, in fecal recovery studies, was recovered intact from the feces. Studies on rate of urinary excretion of the drugs indicated delayed absorption from the enteric coated preparations. Salicylate tablets with in vitro disintegration times as long as two hundred and thirteen minutes were fully available in vivo, whereas a riboflavin preparation with an in vitro disintegration time of one hundred and twenty-eight minutes was only 41% available in vivo. It is suggested that enteric coated tablets should withstand the action of simulated gastric juice for at least sixty minutes, to ensure that these preparations do not disintegrate in the stomach. Furthermore, until quantititive in vivo data are available for individual drugs, it is suggested that to ensure full availability enteric coated preparations, other than salicylates, should disintegrate within thirty minutes in simulated intestinal juice.