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Famotidine

Also indexed as: Mylanta-AR®, Pepcid®, Pepcid® AC

Famotidine is a member of the H-2 blocker (histamine blocker) family of drugs that prevents the release of acid into the stomach. Famotidine is used to treat stomach and duodenal ulcers, reflux of stomach acid into the esophagus, and Zollinger-Ellison syndrome. Famotidine is available as a prescription drug and as a nonprescription product for relief of heartburn, acid indigestion, and sour stomach.

Interactions with Dietary Supplements

Iron
Stomach acid may increase absorption of iron from food. H-2 blocker drugs reduce stomach acid and are associated with decreased dietary iron absorption.1 The iron found in supplements is available to the body without the need for stomach acid. People with ulcers may be iron deficient due to blood loss. If iron deficiency is present, iron supplementation may be beneficial. Iron levels in the blood can be checked with lab tests.

Magnesium-containing antacids
In healthy people, a magnesium hydroxide/aluminum hydroxideantacid, taken with famotidine, decreased famotidine absorption by 20–25%.2 People can avoid this interaction by taking famotidine two hours before or after any aluminum/magnesium-containing antacids. Some magnesium supplements such as magnesium hydroxide are also antacids.

Vitamin B12
Stomach acid is needed for the vitamin B12 in food to be absorbed. H-2 blocker drugs reduce stomach acid and may therefore inhibit absorption of the vitamin B12 naturally present in food. However, the vitamin B12 found in supplements does not depend on stomach acid for absorption.3 Lab tests can determine vitamin B12 levels in people.

Other vitamins and minerals
Some evidence indicates that other vitamins and minerals, such as folic acid4 and copper,5 require the presence of stomach acid for optimal absorption. Long-term use of H-2 blockers may therefore promote a deficiency of these nutrients. Individuals requiring long-term use of H-2 blockers may therefore benefit from a multiple vitamin/mineral supplement.

Interactions with Foods and Other Compounds

Food
Famotidine may be taken with or without food.6 To prevent heartburn after meals, famotidine is best taken one hour before meals.7

Tobacco
In a study of 18 healthy people, cigarette smoking was found to decrease the acid blocking effects of famotidine.8 A double-blind, randomized study of 594 patients with duodenal ulcers found that smoking inhibited the ulcer-healing effect of famotidine.9

Summary of Interactions for Famotidine

Depletion or interference Iron*
Vitamin B12
Adverse interaction Tobacco
Side effect reduction/prevention None known
Supportive interaction None known
Reduced drug absorption/bioavailability None known
Other (see text) Copper
Folic acid
Magnesium

For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

References:

1. Aymard JP, Aymard B, Netter P, et al. Haematological adverse effects of histamine H2-receptor antagonists. Med Toxicol Adverse Drug Exp 1988;3:430–48.

2. Bachmann KA, Sullivan TJ, Jauregui L, et al. Drug interactions of H2-receptor antagonists. Scand J Gastroenterol Suppl 1994;206:14–9.

3. Aymard JP, Aymard B, Netter P, et al. Haematological adverse effects of histamine H2-receptor antagonists. Med Toxicol Adverse Drug Exp 1988;3:430–48.

4. Russell RM, Krasinski SD, Samloff IM. Correction of impaired folic acid (Pte Glu) absorption by orally administered HCl in subjects with gastric atrophy. Am J Clin Nutr 1984;39:656.

5. Tompsett SL. Factors influencing the absorption of iron and copper from the alimentary tract. Biochem J 1940;34:961–9.

6. Lin JH, Chremos AN, Kanovsky SM, et al. Effects of antacids and food on absorption of famotidine. Br J Clin Pharmacol 1987;24:551–3.

7. Threlkeld DS, ed. Gastrointestinal Drugs, Histamine H2 Antagonists, Famotidine. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Sep 1995, 305f–5g.

8. Schurer-Maly CC, Varga L, Koelz HR, Halter F. Smoking and pH response to H2-receptor antagonists. Scand J Gastroenterol 1989;24:1172–8.

9. Reynolds JC, Schoen RE, Maislin G, Zangari GG. Risk factors for delayed healing of duodenal ulcers treated with famotidine and ranitidine. Am J Gastroenterol 1994;89:571–80.