Older adults at high risk for drug interactions

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At least one in 25 older adults, about 2.2 million people in the United States, take multiple drugs in combinations that can produce a harmful drug-drug interaction, and half of these interactions involve a non-prescription medication, according to researchers from the University of Chicago Medical Center.

Although the number of people taking medications has remained stable for the last decade, the number of drugs taken by older people has significantly increased. This may be because of more intense therapy for chronic illness, improved access to medications due to Medicare Part D, and the growth of the generic drug market. More than half of older adults now take five or more medications or supplements.

“Older adults are the largest consumer of prescription drugs,” said study author Stacy Tessler Lindau, MD, assistant professor of obstetrics and gynecology and of medicine at the University of Chicago Medical Center. “We find that they commonly combine these prescription medications with over-the-counter medications and dietary supplements, which can increase their vulnerability to medication side-effects and drug-drug interactions.

The study used data collected for the National Social Life, Health and Aging Project, a nationally representative multi-purpose survey of adults aged 57 to 85 administered between July 2005 and March 2006. The survey team interviewed 3,005 participants in their homes about the medications they used on a regular schedule, like every day or every week.

Ninety-one percent of all respondents regularly used at least one medication, a percentage that increased with age. Twenty-nine percent of older adults took more than five prescription medications.

Sixty-eight percent of the adults who took prescription drugs also used over-the-counter medications or dietary supplements. Men were more likely to take over-the-counter medicines. Women were more likely to use supplements, such as vitamins or herbal remedies.

Nearly half of the drug-drug interactions identified could cause bleeding problems. One of the most common was taking warfarin, a prescription drug designed to prevent blood clots, along with an over-the-counter drug such as aspirin, which also interferes with clotting.

“Physicians and pharmacists need to ask their patients about the use of nonprescription medications,” said Lindau. “Patients need to inform their providers about all medications they use — prescription and nonprescription — and should ask their physician or pharmacist about interactions any time they start a new drug, on their own or following the doctor’s recommendation.”

Carrying a list of all medications in a wallet might be a good idea, the authors suggest. So is using the same pharmacy or chain for all medications. — Newswise