Zollinger-Ellison syndrome (up to 120 mg daily). Animal experiments with ultra-high doses of rabeprazole have demonstrated lethality through unknown mechanisms. The lethal overdose syndrome in animals is characterized by convulsion and coma. Interactions Drug-drug interactions Rabeprazole does not interfere with the plasma concentration of drugs that are also metabolized by the same enzymes (i.e. CYP2C19) that it is metabolized by. Therefore, it is not expected to react with CYP2C19 substrates like theophylline, warfarin, diazepam, and phenytoin. However, the acid-suppression effects of rabeprazole, like other PPIs, may interfere with the absorption of drugs that require acid, such as ketoconazole and digoxin. There is some evidence that omeprazole and esomeprazole, two medications in the same class as rabeprazole, can disturb the conversion of an anticoagulant medication called clopidogrel to its active metabolite. However, because this is thought to be mediated by the effect of omeprazole and esomeprazole on CYP2C19, the enzyme that activates clopidogrel, this drug interaction is not expected to occur as strongly with rabeprazole. However, whether the effect of omeprazole and esomeprazole on clopidogrel's metabolism actually leads to poor clinical outcomes is still a matter of intense debate among healthcare professionals. Clinically serious drug-drug interactions may involve the acid-suppression effects of rabeprazole. For example, rabeprazole should not be used concomitantly with rilpivirine, an anti-HIV therapy, which requires acid for absorption. Lowered plasma concentrations of rilpivirine could lead to progression of HIV infection. Other drugs that require acid for absorption include antifungal drugs like ketoconazole and itraconazole, digoxin, iron, mycophenolate, and tyrosine kinase inhibitors like erlotinib, dasatinib, and nilotinib. There is no clinically relevant drug interaction between rabeprazole and antacids. Food-drug interactions Food does not affect the amount of rabeprazole that enters the body, but it does delay its onset of effect by about 1.7 hours. Pharmacology Mechanism of action Rabeprazole's mechanism of action first involves getting absorbed into the parietal cells of the stomach, which are the cells that are responsible for secreting hydrochloric acid (HCl). At this point, rabeprazole is inactive. However, rabeprazole is then secreted into the secretory canaliculus of the parietal cells, which is the space from which acid secretion occurs. Here, acid secretion is mediated by the energy-dependent acid pumps, called hydrogen potassium adenosine triphosphatase (H+/K+ ATPase) pumps. These enzymatic pumps have cysteine amino acid residues. After being activated by gastric (stomach) acid to a reactive sulfenamide intermediate, rabeprazole permanently binds the cysteine residues, forming covalent,