Pariet Drug Interactions

Sodium rabeprazole, as is the case with other members of the proton-pump inhibitor (PPI) class of compounds, is metabolized through the cytochrome P-450 (CYP450) hepatic drug metabolizing system. Studies in healthy subjects have shown that sodium rabeprazole does not have clinically significant interactions with the drugs studied including warfarin, phenytoin, theophylline or diazepam metabolized by the CYP450 system.
Sodium rabeprazole produces a profound and long lasting inhibition of gastric acid secretion. An interaction with compounds whose absorption is pH-dependent may occur, therefore, the potential for such interaction was investigated. Co-administration of sodium rabeprazole results in a 33% decrease in ketoconazole levels and a 22% increase in trough digoxin levels in normal subjects. Therefore, individual patients may need to be monitored to determine if a dosage adjustment is necessary when such drugs are taken concomitantly with Pariet. Rabeprazole does not adversely influence plasma concentrations of amoxicillin or clarithromycin when co-administered for the purpose of eradicating upper gastrointestinal H. pylori infection.
In clinical trials, antacids were used concomitantly with the administration of Pariet and, in a specific study designed to define this interaction. It has been reported that the mean plasma AUC decreases by 8% and 6% after simultaneous Pariet-antacid containing aluminium hydroxide gel/magnesium hydroxide co-administration and Pariet administration 1 hr after antacid containing aluminium hydroxide gel/magnesium hydroxide administration respectively, compared to Pariet administration alone. There was no clinically relevant interaction with food.
In vitro studies with human liver microsomes indicated that sodium rabeprazole is metabolized by isoenzyme of CYP450 (CYP2C19 and CYP3A4). In these studies, at expected human plasma concentrations, rabeprazole neither induces nor inhibits CYP3A4; and although in vitro studies may not always be predictive of in vivo status, these findings indicate that no interaction is expected between rabeprazole and cyclosporin.