.
Cimetidine is a member of the H-2 blocker (histamine blocker) family of drugs that prevents the release of acid into the stomach. Cimetidine is used to treat stomach and duodenal ulcers, reflux of stomach acid into the esophagus, and Zollinger-Ellison syndrome. Cimetidine is available as a prescription drug and as a nonprescription over-the-counter product for relief of heartburn.
Interactions with Dietary Supplements
Iron
Stomach acid may facilitate iron absorption. H-2 blocker drugs reduce stomach acid and are
associated with decreased dietary iron absorption.1 People with ulcers may also be
iron deficient due to blood loss and benefit from iron supplementation. Iron levels in the
blood can be checked with lab tests.
Magnesium
In healthy volunteers, a magnesium hydroxide/aluminum hydroxideantacid, taken with cimetidine, decreased cimetidine absorption by
20 to 25%.2 People can avoid this interaction by taking cimetidine two hours before
or after any aluminum/magnesium-containing antacids, including magnesium hydroxide found in
some vitamin/mineral supplements. However, the
available studies do not clearly indicate if magnesium hydroxide was the problem and may not
need to be avoided.
Vitamin B12
Hydrochloric acid is needed to release vitamin B12 from food so it can be absorbed by the
body. Cimetidine, which reduces stomach acid, may decrease the amount of vitamin B12 available
for the body to absorb.3 The vitamin B12 found in supplements is available to the
body without the need for stomach acid. Lab tests can determine vitamin B12 levels in
people.
Vitamin D
Cimetidine may reduce vitamin D activation by the liver.4 Lab tests can measure
activated vitamin D levels in the blood. Forms of vitamin D that do not require liver
activation are available, but only by prescription.
Interactions with Foods and Other Compounds
Food
Cimetidine may be taken with or without food.
Caffeine
Caffeine is found in coffee, tea, soft drinks, chocolate,
guaraná (Paullinia cupana), nonprescription over-the-counter drug
products, and supplement products containing caffeine or guaraná. Cimetidine may decrease
the clearance of caffeine from the body, causing increased caffeine blood levels and unwanted
actions.5 People taking cimetidine may choose to limit their caffeine intake to
avoid problems. They should read food, beverage,
drug, and supplement labels carefully for caffeine content.
Summary of Interactions for Cimetidine
| Depletion or interference | Iron Vitamin B12 Vitamin D |
|---|---|
| Adverse interaction | Caffeine* |
| Side effect reduction/prevention | None known |
| Supportive interaction | None known |
| Reduced drug absorption/bioavailability | 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. Salom IL, Silvis SE, Doscherholmen A. Effect of cimetidine on the absorption of vitamin B12. Scand J Gastroenterol 1982;17:129–31.
4. Anonymous. Cimetidine inhibits the hepatic hydroxylation of vitamin D. Nutr Rev 1985;43:184–5 [review].
5. Threlkeld DS, ed. Central Nervous System Drugs, Analeptics, Caffeine. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Feb 1998, 230–d.
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The information presented in VitaminLore 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.