Senior Prescription Medications Are Not the Only Cause of Drug Interactions

Seniors are at a greater risk of drug interactions than the general population as they typically take more medications. Taken in certain combinations, drugs can interfere or interact with one another, altering their effectiveness in controlling symptoms and improving health. In some cases the results can be life-threatening.

A University of Chicago Medical Center study published in the Dec. 24/31, 2008, issue of the Journal of the American Medical Association stated that more than half of American seniors take five or more medications or supplements. The study further found that at least one in 25 older Americans—about 2.2 million—take drugs in potentially harmful combinations.

The problem of medication interactions does not involve only prescription medications. The study found that about half of the interactions involved over-the-counter (OTC), or nonprescription medications. Herbal medications, supplements and vitamins—and even some foods and beverages—also interact with drugs to alter their performance.

The following are just a few examples of how nonprescription products can interact with prescription drugs for unhealthy results:

  • Taken separately, aspirin and warfarin help prevent blood clots from forming. Taken together, they may cause excessive bleeding.
  • Decongestants, found in many OTC cold remedies, may increase blood pressure of people taking anti-hypertension medications or MAO inhibitors, a type of antidepressant.
  • Certain antacids can diminish the effectiveness of many medicines, such as antibiotics and heart medications, by preventing them from being absorbed into the blood stream.

The National Council on Patient Information and Education (NCPIE) recommends knowing the active ingredients in the medicines you take. For instance, OTC pain relievers commonly contain one or more of four different pain relief ingredients—aspirin, naproxen, ibuprofen and acetaminophen. A number of prescription and OTC multi-symptom cold and flu medicines contain these same active ingredients.

Clients should avoid combining medicines with the same active ingredients as this could lead to an overdose of the ingredient.
Food can also alter the effectiveness of medication. NCPIE cites examples:

  • Dairy products, antacids and vitamins containing iron can slow the body’s absorption of antibiotics into the bloodstream and thus diminish their effectiveness.
  • Grapefruit and grapefruit juice block enzymes that metabolize certain drugs, thus making them less effective. Drugs affected by grapefruit include some blood pressure-lowering medications, some cholesterol drugs, the antihistamine terfenadine, and cyclosporine, a drug taken to prevent organ transplant rejection. Pomelo and Seville oranges can cause similar effects.

If you do not know whether any of your medications interacts with foods, ask your doctor or pharmacist.

Some Ways to Prevent Senior Drug Interactions

On its Web site,, the NCPIE provides advice on preventing drug interactions, such as:

  • Give each of your doctors a complete list of all the prescription and OTC drugs, herbal products and supplements you are taking
  • Read and follow label directions exactly, taking no more than the recommended amount
  • Ask a doctor or pharmacist any questions you may have about a medication before taking it
  • Choose an OTC medication that will treat only the symptoms you have
  • Be cautious when taking more than one OTC drug concurrently as they may contain the same active ingredients, giving you more than the recommended dose
  • Do not combine nonprescription drugs, herbal medicines, vitamins or supplements with prescription medications without consulting your doctor
  • Do not use medicines after their expiration date
  • Use the same pharmacy for all prescriptions to avoid being given medications that have adverse interactions

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