Dangerous drug combos pose risk for elderly

"Older adults in the United States use medicine and they use a lot of it," said Dr. Stacy Tessler Lindau of the University of Chicago Medical Center in Illinois, whose study appears in the Journal of the American Medical Association.

"While medications are often beneficial, they are not always safe," she said in a telephone interview.

She noted a recent report that estimated U.S. adults over 65 make up more than 175,000 emergency department visits a year for adverse drug reactions, and commonly prescribed drugs accounted for a third of these visits.

For the study, Lindau teamed up with Dima Qato, a pharmacist and researcher at the University of Chicago. They used data from a national survey of adults aged 57 to 85 and interviews with nearly 3,000 people in their homes to get a read on the medications they used on a regular basis.

They analyzed potential interactions among the top 20 prescription and over-the-counter drugs and the top 20 dietary supplements, and found that 68 percent of adults surveyed who took prescription drugs also used over-the-counter drugs or dietary supplements. Men in the 75 to 85-year-old age group were at the highest risk, they said. "One in 10 men between the ages of 75 to 85 were at risk for a drug-to-drug interaction," Qato said in a telephone interview.

Nearly half of the potential drug-to-drug interactions could cause bleeding problems. The blood thinner warfarin, often sold by Bristol-Myers Squibb Co. under the brand name Coumadin, was most commonly cited in potentially dangerous combinations.

Some 2 million Americans take warfarin after a heart attack, stroke or major surgery. The team found warfarin was commonly teamed up with aspirin, a drug often taken to prevent heart attacks that also interferes with clotting.  Warfarin and the cholesterol-lowering statin drug simvastatin, which is sold by Merck & Co under the brand name Zocor, was another combination that could cause potential bleeding risks.

Among non-prescription drugs, they found many people were taking the popular nutritional supplement Ginkgo biloba in combination with aspirin, another potential cause of bleeding. The team was reassured that they found no instances of people taking absolutely forbidden drug combinations, but the finding of widespread use of drugs that could cause major drug reactions was worrisome.

"We think the patient needs to know about these risks," Qato said.

The researchers recommend patients carry a list in a wallet or purse of all of the drugs and supplements they take.  And they said doctors, pharmacists and other health professionals should remember to ask about all of the medications their patients are taking.