Drug Interactions Newsletter

Volume 2, Issue 10, 03/09/2010

Question

Is there any evidence that has determined the impact histamine-2 receptor antagonists (H2RA) have on oral iron replacement therapy?

Answer

It is estimated that approximately 10% of people in developed nations and 25-50% in developing nations are iron deficient thereby putting them at increased risk for microcytic, hypochromic anemia.(1,2)  While some patients can increase their iron stores through a proper diet, most will need iron replacement therapy.  The most common form of iron replacement in clinical practice is the use of oral iron or ferrous (Fe2+) forms of iron at doses that provide 200 mg of elemental iron per day.(3)  Unfortunately, oral iron therapy is not only difficult to tolerate, but its absorption is influenced by a number factors which includes the type of iron product used, the presence of food, other medications, the anatomy of the stomach and small intestine, and the acidity of the environment in the areas of absorption.(1,3-9)  The influence of gastric acidity is the focus for this drug interaction.  As such the use of histamine-2 receptor antagonists (H2RA) such as cimetidine, famotidine, and ranitidine have the potential to influence iron's bioavailability since they can increase the gastric pH.

The mechanism for the absorption of orally administered iron therapy and the potential interaction with H2RAs was previously answered (PW Drug Interact Newsl 2009;1(44):1-5.)...

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