Among older adults, prescription and over-the-counter medications are commonly used together

December 23, 2008

A survey suggests that nearly half of older adults in the U.S. use prescription and over-the-counter medications together, and that about 4 percent of older adults are potentially at risk of an adverse drug reaction because of an interaction between medications, according to a study in the December 24/31 issue of JAMA. The researchers also found that nearly 30 percent use at least 5 prescription medications.

Rates of prescription medication use have increased considerably over the last several decades, as have the rates of use of over-the-counter medications and dietary supplements. Older adults are the largest per capita consumers of prescription medications and the most at risk for medication-related adverse events, according to background information in the article. "Despite concerns about drug safety and new federal policies to improve older adults' access to medications, current information on their concurrent [regular use of at least 2 medications] use of prescription medications, over-the-counter medications, and dietary supplements is limited," the authors write.

Dima M. Qato, Pharm.D., M.P.H., of the University of Chicago, and colleagues analyzed data from a survey to estimate the prevalence and patterns of medication use (including concurrent use) and major drug-drug interactions among older adults, age 57 through 85 years. The survey included 3,005 community-residing individuals, who were drawn from a cross-sectional, nationally representative sample of the United States. In-home interviews, including medication logs, were administered between June 2005 and March 2006. Medication use was defined as prescription, over-the-counter, and dietary supplements used "on a regular schedule, like every day or every week." The survey response rate was about 75 percent.

During 2005 to 2006, 91 percent of older adults, corresponding to 50.5 million adults age 57 to 85 years, regularly used at least 1 medication. Among all medication types, prescription medication use was the most prevalent, used by 81 percent, or an estimated 44.9 million older adults. The prevalence of prescription medication use was highest among the oldest age group, age 75 to 85 years. Nearly one-half of older adults regularly used at least 1 over-the-counter medication or dietary supplement. Women were more likely to use prescription medications and dietary supplements than men, whereas use of over-the counter medications was similar among women and men.

More than half of older adults used 5 or more prescription medications, over-the-counter medications or dietary supplements. For prescription medications, 29 percent of all respondents used more than 5 medications. The prevalence of the use of 5 or more prescription medications increased steadily with age for both men and women and was overall significantly higher among women.

Overall, 68 percent of older adults using prescription medications were concurrently using over-the-counter medications, dietary supplements, or both. The researchers also found that 1 in 25 (4 percent) older adults (approximately 2.2 million) were at risk for a major potential drug-drug interaction. The rate of any major medication interaction increased with age for both men and women but was higher among men compared with women across all age groups. More than half of these major interactions involved the use of nonprescription therapies. In addition, nearly half involved the use of anticoagulants (e.g., warfarin) or antiplatelet agents (e.g., aspirin).

"Several factors have likely contributed to this increase in the rate of [the use of five or more medications] among older adults over the last decade. These include intensification of therapy for common chronic medical conditions (e.g., diabetes, cardiovascular disease), increased access to medications because of policy changes (e.g., Medicare Part D and assistance programs), and growth of the generic drug market," the authors write.

"One recent report estimated that U.S. adults older than 65 years make more than 175,000 emergency department visits annually for adverse drug events; commonly prescribed medications accounted for one-third of these events," the researchers note. "Our findings suggest that concurrent use of prescription and nonprescription medications in older adults remains a public health problem and could be an important focal point for further improvements in drug safety for seniors."

"Medications are a critical modality for prolongation of life and improved quality of life for many older adults. By establishing patterns of prescription and nonprescription medication use among older adults, these data may help support efforts to increase the safety and quality of pharmacotherapy for older adults," the authors conclude.
-end-
(JAMA. 2008;300[24]:2867-2878. Available pre-embargo to the media at www.jamamedia.org)

Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

The JAMA Network Journals

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