Interactions between Omeprazole and Rifampicin

Mechanism of Interaction

• The American Thoracic Society notes that rifampicin is a potent inducer of the hepatic microsomal enzymes, specifically cytochrome P450 (CYP2C19 and CYP3A4), which are the primary metabolic pathways of omeprazole 1
• The American Heart Association recommends considering alternative therapies, such as H2 antagonists (anti-H2), like famotidina or nizatidina, which are not significantly metabolized by the cytochrome P450 system and have a low potential for interaction with rifampicin 2

Clinical Consequences

• The American College of Gastroenterology warns that concomitant administration of rifampicin decreases omeprazole concentrations, potentially resulting in reduced gastric acid suppression and therapeutic failure of omeprazole 1

Management Recommendations

• The FDA label for omeprazole advises avoiding concomitant use of omeprazole with rifampicin, and the American Thoracic Society recommends considering alternative therapies or adjusting the dose of omeprazole 1

Alternative Strategies

• The American Heart Association suggests considering H2 antagonists, such as famotidina or nizatidina, as alternative therapies, as they have a low potential for interaction with rifampicin 2

Important Temporal Considerations

• The American Thoracic Society notes that the inductive effect of rifampicin develops gradually during treatment, and it is essential to reduce the dose of omeprazole within 2 weeks after discontinuing rifampicin to avoid relative overdose 1

Context in Tuberculosis Treatment

• The Centers for Disease Control and Prevention (CDC) recommend being aware of this interaction when treating patients with tuberculosis who require gastric acid suppression, as rifampicin interacts with numerous medications metabolized by the liver, including oral anticoagulants, hormonal contraceptives, glucocorticoids, and anticonvulsants 1, 3, 4