Omeprazole Also indexed as: Losec, Prilosec
Omeprazole is a member of the proton pump inhibitor family of drugs, which blocks production of stomach acid. Omeprazole is used to treat diseases in which stomach acid causes damage, including gastric and duodenal ulcers, gastroesophageal reflux disease, erosive esophagitis, and Zollinger-Ellison syndrome.
Summary of Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem contradictory. For clarification, read the full article for details about the summarized interactions.
 May Be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them. | Calcium Folic acid Vitamin B12* Vitamin C |
| May Be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication. | Cranberry* |
 Avoid: Reduced drug absorption/bioavailability—Avoid these supplements when taking this medication since the supplement may decrease the absorption and/or activity of the medication in the body. | St. John's wort |
| Supportive interaction | None known |
| Adverse interaction | None known |
An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
Interactions with Dietary Supplements
Calcium
In a study of elderly women, administration of omeprazole decreased the absorption of calcium,1 presumably because the drug decreased the stomach's production of hydrochloric acid, which is necessary for calcium absorption. The form of calcium used in the study to test calcium absorption was calcium carbonate. Drugs that reduce stomach acid secretion may not inhibit other forms of calcium, such as calcium citrate.2
Folic acid
Folic acid is needed by the body to utilize vitamin B12. Antacids, including omeprazole, inhibit folic acid absorption.3 People taking antacids are advised to supplement with folic acid.
Vitamin B12
Omeprazole interferes with the absorption of vitamin B12 from food (though not from supplements) in some4 5 6 7 but not all8 9 studies. A true deficiency state, resulting in vitamin B12-deficiency anemia, has only been reported in one case.10 The fall in vitamin B12 status may result from the decrease in stomach acid required for vitamin B12 absorption from food caused by the drug.11 This problem may possibly be averted by drinking acidic juices when eating foods containing vitamin B12.12
However, all people taking omeprazole need to either supplement with vitamin B12 or have their vitamin B12 status checked on a yearly basis. Even relatively small amounts of vitamin B12 such as 10–50 mcg per day, are likely to protect against drug induced vitamin depletion.
Vitamin C
Treatment of healthy volunteers with omeprazole for four weeks resulted in a 12.3% decrease in blood levels of vitamin C.13
Interactions with Herbs
St. John's wort
In a study of healthy human volunteers, supplementing with St. John's wort greatly decreased omeprazole blood levels by accelerating the metabolism of the drug.14 Use of St. John's wort may, therefore, interfere with the actions of omeprazole.
Cranberry (Vaccinium marocarpon)
People taking omeprazole may increase absorption of dietary vitamin B12 by drinking cranberry juice or other acidic liquids with vitamin B12-containing foods.15
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. O'Connell MB, Madden DM, Murray AM, et al. Effects of proton pump inhibitors on calcium carbonate absorption in women: a randomized crossover trial. Am J Med 2005;118:778–81.
2. (Recker RR. Calcium absorption and achlorhydria. N Engl J Med 1985;313:70–3.
3. Russell RM, Golner BB, Krasinski SD, et al. Effect of antacid and H2 receptor antagonists on the intestinal absorption of folic acid. J Lab Clin Med 1988;112:458–63.
4. Marcuard SP, Albernaz L, Khazanie PG. Omeprazole therapy causes malabsorption of cyanocobalamin (Vitamin B12). Ann Intern Med 1994;120:211–5.
5. Termanini B, Gibril F, Sutliff VE, et al. Effect of long-term gastric acid suppressive therapy on serum vitamin B12 levels in patients with Zollinger-Ellison syndrome. Am J Med 1998;104:422–30.
6. Koop H. Review article: metabolic consequences of long-term inhibition of acid secretion by omeprazole. Aliment Pharmacol Ther 1992;6:399–406 [review].
7. Bellou A, Aimone-Gastin I, De Korwin JD, et al. Cobalamin deficiency with megaloblastic anaemia in one patient under long-term omeprazole therapy. J Intern Med 1996;240:161–4.
8. Koop H, Bachem MG. Serum iron, ferritin, and vitamin B12 during prolonged omeprazole therapy. J Clin Gastroenterol 1992;14:288–92.
9. Schenk BE, Festen HP, Kuipers EJ, et al. Effect of short-and long-term treatment with omeprazole on the absorption and serum levels of cobalamin. Aliment Pharmacol Ther 1996;10:541–5.
10. Bellou A, Aimone-Gastin I, De Korwin JD, et al. Cobalamin deficiency with megaloblastic anaemia in one patient under long-term omeprazole therapy. J Intern Med 1996;240:161–4.
11. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption. J Am Coll Nutr 1994;13:584–91.
12. Bradford GS, Taylor CT. Omeprazole and vitamin B12 deficiency. Ann Pharmacother 1999;33:641–3 [review].
13. Henry EB, Carswell A, Wirz A, et al. Proton pump inhibitors reduce the bioavailability of dietary vitamin C. Aliment Pharmacol Ther 2005;22:539–5.
14. Wang LS, Zhou G, Zhu B, et al. St John's wort induces both cytochrome P450 3A4-catalyzed sulfoxidation and 2C19-dependent hydroxylation of omeprazole. Clin Pharmacol Ther 2004;75:191–7.
15. Saltzman JR, Kemp JA, Golner BB, et al. Effect of hypochlorhydria due to omeprazole treatment or atrophic gastritis on protein-bound vitamin B12 absorption. J Am Coll Nutr 1994;13:584–91.
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires February 2010.
