Correlation of in vitro and in vivo methodology for evaluation of antacids.

The rate and extent of acid consumption of an antacid suspension and tablet were evaluated by in vitro and in vivo techniques. Four different test procedures were used to estimate in vitro antacid reactivity. In vivo effects were determined in the fasted and postcibal states in normal human subjects by a radiotelemetry procedure. The duration of elevation of intragastric pH greater than 3 was in agreement with in vitro estimates of total acid consumption of the antacid. There was also good correlation between onset, extent, and duration of in vivo antacid activity and a modified in vitro Beekman antacid test procedure. There was no significant difference in antacid activity of the tablet or suspension in either in vitro or in vivo test procedures. A wide variation in antacid activity was observed between subjects and also in the fasted versus postcibal states. These studies emphasize the requirements for standardization of antacid products by comparactive in vitro and in vivo evaluations to facilitate individualized dose titration of the antacid in each patient and correlation of the acid secretion rate in various types of GI disease with the antacid dose.