Older adults are the most likely people to use prescription medications. Many also take non-prescription drugs like aspirin and vitamin supplements, putting them at risk for dangerous drug interactions.
"The number of medications older adults are taking is increasing, and we worry about the potential interactions," said Dr. Tessler Lindau of the University of Chicago Medical Center.
"Combinations of medications may reduce the effectiveness of one or the other medication," he said. Combinations can lead to internal bleeding and other serious problems.
Researchers at the University of Chicago studied medication use among older adults.
No one has ever really documented how many medications, what types of medications older people use on such a large scale, including non-prescription drugs along with prescription drugs," pharmacist Dima Qato said.
The study, which is published in the Journal of the American Medical Association, analyzed data from more than 3,000 people aged 57 to 85. They were asked about prescription drug use and the use of non-prescription medicines like aspirin and herbal supplements.
The study showed that 81 percent of study participants used at least one prescription medication and that 68 percent of those who took prescription drugs also used over-the-counter medication, dietary supplements or both.
"One in 10 were using combinations of drugs that put them at risk for severe medication interaction," Lindau said. Nearly 4 percent of those studied were at risk for major, hazardous drug interaction. The risk was highest for men ages 75 to 85.
Researchers recommend that doctors and pharmacists be careful when prescribing and dispensing drugs and that patients discuss all medications they are taking with their doctors, including those they buy over the counter.