Also indexed as: Tagamet, Tagamet HB
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 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
| 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.
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.
Avoid: Adverse interaction—Avoid these supplements when taking this
medication because taking them together may cause undesirable or dangerous results.
|Side effect reduction/prevention
An asterisk (*) next to an item in the summary indicates that the
interaction is supported only by weak, fragmentary, and/or contradictory scientific
Interactions with Dietary Supplements
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.
In healthy volunteers, a magnesium
hydroxide/aluminum hydroxide antacid,
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
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
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
Cimetidine may be taken with or without food.
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
1. Aymard JP, Aymard B, Netter P, et al. Haematological adverse effects
of histamine H2-receptor antagonists.Med Toxicol Adverse Drug Exp
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