What is iron?

Most people receive enough iron through their diet; an essential mineral for red blood cells. In fact, almost three-quarters of the body’s iron can be found inside red blood cells; their role involving, in part, the transport of oxygen and carbon dioxide around the body.

Food sources high in iron include red meat, poultry, lentils, beans, green-leafy vegetables and liver. The bioavailability of iron from plant sources is substantially lower than from meat sources. In practical terms, this means that vegetarians/vegans need to consume more iron than meat-eaters.

Many people are diagnosed with iron deficiency for a wide range of reasons – causes include chronic bleeding, inadequate dietary intake of iron, taking drugs that interfere with iron absorption, malabsorption syndromes, amongst others.

Iron levels need to be replenished but with this replenishment – whether from supplements or dietary sources – comes the risk of iron interactions with other foods or drugs. Here, we sketch out some examples of these iron interactions.

Common iron interactions

There are three main, different ways in which iron interactions can manifest:

  1. Drugs that reduce the absorption of iron
  2. Iron that decreases the absorption of other drugs
  3. Drugs that increase iron levels

We’ll go through each of these in turn.

First, drugs that reduce the iron absorption. These drugs are few but their effects still hold clinical significance. Colestipol and cholestyramine (lipid-lowering agents of the bile acid sequestrant class) are, for example, known to reduce iron absorption.

Drug Interactions with Iron

Drugs that affect stomach acid production, such as H2 antagonists and proton pump inhibitors, also impair iron absorption. H2 antagonists include famotidine and ranitidine, whereas proton pump inhibitors include omeprazole and pantoprazole.

Second, iron as a substance that reduces absorption of other drugs. Iron reduces the absorption of quinolones, ACE inhibitors, bisphosphonates and tetracyclines. Iron may also reduce the effectiveness of levothyroxine and carbidopa/levodopa.

Third and finally, drugs that can increase iron levels. Members of this class include birth control medicines. It’s worth noting that some iron interactions are more pronounced than others, whereas some interactions have somewhat limited effects.

Overcoming iron interactions

Patients are often recommended, when faced with the above interactions, not to consume iron supplements within 2 hours of taking the implicated medicine – both before and after. This eliminates the contact risk between supplement and drug and/or drug effects.

Think about tetracyclines. The effect of tetracycline antibiotics is reduced when they are taken with iron supplements. Iron works to chelate the tetracycline structure, inactivating its therapeutic potential. Iron needs to be avoided while the antibiotic is being absorbed.

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