Drug Interactions between omeprazole and Vitamin B12

By reducing or suppressing gastric acid secretion, H2-receptor antagonists and proton pump inhibitors may interfere with the gastrointestinal absorption of vitamin B12, a process that is dependent on the presence of gastric acid and pepsin. Clinical studies have shown that dietary (i.e., protein-bound) vitamin B12 malabsorption can occur during treatment with these agents, particularly proton pump inhibitors, although the likelihood of developing clinically significant deficiency over time is unknown. There has been one reported case of vitamin B12 deficiency with megaloblastic anemia in a patient who received omeprazole at a minimum of 40 mg/day for 4 years. Also uncertain is whether acid reduction or suppression can affect the absorption of vitamin B12 ingested in the form of oral supplements such as cyanocobalamin. Non-oral routes of administration (e.g., parenteral, intranasal, sublingual) are generally preferred in the treatment of B12 deficiency-related anemia.