TUESDAY, Dec. 23, 2008 (HealthDay News) -- As many as 4 percent of older adults in the United States combine over-the-counter medications with prescription drugs in ways that put them at risk for potentially dangerous interactions, a new survey finds.
A recent report estimated that adults over 65 account for more than 175,000 emergency department visits for adverse drug reactions each year, and commonly prescribed medications accounted for 33 percent of these drug reactions.
"The vast majority of older adults are using at least one medication and more adults are using more medications, particularly prescription medications, compared to a decade ago," said survey author Dima M. Qato, from the University of Chicago.
In addition, almost 30 percent of seniors are taking at least five prescription medications and many combine prescription and nonprescription drugs. Among commonly used medications, drug-to-drug interactions extend beyond prescription drugs, with nearly half involving the use of over-the-counter medications or dietary supplements.
"And despite limited availability of drug safety information for nonprescription medications, particularly dietary supplements, they are frequently used in older adults," Qato added.
Patients need to know that while medications are often beneficial, there are often risks associated with their use, Qato said.
"If they need to self-medicate with over-the-counter drugs or dietary supplements, they should consult with their physician or pharmacist. This is particularly important in older people because as people get older, they are more vulnerable to the negative effects of medications, including drug-to-drug interactions," Qato said.
The report is published in the Dec. 24/31 issue of the Journal of the American Medical Association.
For the study, Qato's team used survey data collected on more than 3,000 adults aged 57 to 85. The researchers looked for all medications, both over-the-counter and prescription, used between June 2005 and March 2006.
The researchers found that 91 percent of U.S. adults, about 50.5 million, used at least one medication regularly. Prescription medicines were used by 81 percent of adults, or 44.9 million older Americans. Most medications were used by those 75 to 85 years old.
In addition, almost 50 percent of older adults used at least one over-the-counter medication or dietary supplement. More women than men used prescription medications and dietary supplements. However, the use of over-the-counter medications was the same for men and women, the researchers found.
More than 50 percent of those surveyed used five or more prescription drugs, over-the-counter medications or dietary supplements. Among those taking prescription medications, 29 percent used more than five drugs and drug use increased with age among both men and women, Qato's group reports.
In addition, the researchers found that 68 percent of older adults used prescription drugs plus over-the-counter medications or dietary supplements. Among those combining drugs, 4 percent were in danger of having an adverse drug reaction.
Moreover, the rate of adverse drug interactions increased with age, particularly among women. Over 50 percent of these interactions involved the use of over-the-counter medications, the researchers found.
The most common adverse interactions occurred with blood thinners such as warfarin and antiplatelet drugs such as aspirin, Qato's group found.
"Physicians and pharmacists need to ask older patients about all the medications they use -- prescription and nonprescription -- and patients need to be prepared to share this information," Qato said. "This is especially important in patients who see multiple providers and patients that fill at multiple pharmacies."
Dr. Laurie Jacobs, chief of geriatric medicine at Montefiore Medical Center in New York City, believes that the potential for adverse drug reactions by mixing drugs is great and patients need to coordinate their medication use with one doctor to guard against harmful interactions.
"No one is looking over the number of medicines they are on to look for potential interactions," Jacobs said. "Someone other than the patient should go over the whole list."
Jacobs noted that the increase in the number of people taking drugs is a good thing. "There has been an intensification of therapy for disease," she reasoned.
However, there has also been a growth in the number of medications and an increased effort in marketing them, which makes people seek out doctors who will prescribe them, Jacobs said. In addition, there has also been an increase in the use of supplements, she noted.
"Often patients have difficulty evaluating the appropriateness of supplements with their own medical problems," Jacobs said. "They are not seeking the advice of their physician on supplement use," she said.
Common adverse drug reactions include:
- Lisinopril (Prinivil) plus potassium can elevate blood-potassium levels and disrupt heart rhythm.
- Warfarin (Coumadin) plus simvastatin (Zocor) can increase bleeding risk.
- Warfarin (Coumadin) plus aspirin can increase bleeding risk.
- Atorvastatin (Lipitor) plus niacin can cause muscle weakness, muscle breakdown
- Simvastatin (Zocor) and niacin can cause muscle weakness and muscle breakdown.
- Ginkgo plus aspirin can increase bleeding risk.
More information
For more information on drug interactions, visit the U.S. National Library of Medicine .
