Effect of concomitant antacid administration on plasma cimetidine concentrations during repetitive dosing.

Previous research has suggested that concurrent administration of antacid and cimetidine results in lower than expected plasma levels of cimetidine. Because these studies were all of single-dose design, this study was undertaken to determine the nature of the interaction after repeated administration of both drugs. There was no statistically significant difference demonstrated for any of the pharmacokinetic parameters evaluated in the study. Based on these findings, the previous recommendation that administration of antacid and cimetidine be separated in time may not be necessary.