Drug Interactions Newsletter
Volume 1, Issue 44, 11/17/2009
Question
What is the mechanism by which histamine-2 receptor antagonists (H2RA) decrease the absorption (or bioavailability) of oral iron replacement in patients with iron deficiency anemia?
Answer
Oral iron supplementation is most commonly prescribed to patients with iron deficiency anemia and is one of the most common nutritional deficiencies world-wide. It is estimated that approximately 10% of people in developed nations and 25-50% in developing nations are iron deficient.1 Iron is an essential trace mineral that our bodies primarily utilize for carrying out cellular respiration (electron transport chain) and to carry oxygen to our tissue in the form of hemoglobin.2 Without adequate concentrations of iron, hemoglobin will not adequately be made thereby resulting in the formation of microcytic, hypochromic anemia (smaller and more pale red blood cells).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, such as ferrous sulfate, 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 of factors which includes the type of iron product used, the presence of food or other medications, the anatomy of the stomach and small intestine, and the acidity of the environment in the areas of absorption.1,3-7 The influence of gastric acidity is the focus for this drug interaction newsletter.
What is the
normal process for absorption of oral iron and what role does gastric acidity
have on this process?
Iron can come in
several different forms with each having a different bioavailability. Iron in food can be in the form of
either...
The complete answer to this question comes with a figure that shows this mechanism behind this drug-drug interaction.
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