Fifteen percent of older adults are at risk for a major drug-drug interaction due to increased use of prescription medications, over-the-counter (OTC) medicines, and dietary supplements, including concurrent use of interacting medications, a study published in JAMA Internal Medicine has shown.1

Older adults commonly use prescription medications, OTC medicines, and dietary supplements both in combination and alone; however, what drives this use, as well as the potential for drug-drug interactions, are not well-known. Researchers sought to characterize the prevalence of prescription drugs, OTC medicines, and dietary supplements use alone and concurrently among older adults age 62 to 85 years.

For the study, the researchers conducted in-home interviews with direct medication inspection in 2005-2006 and in 2010-2011. Medication use was defined as the use of at least 1 prescription, OTC, or dietary supplement daily or weekly; concurrent use was defined as the use of 2 or more such products.

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The first cohort (2005-2006) consisted of 2351 participants, mean age 70.9 years, and 53% were female. The second cohort (2010-2011) consisted of 2206 participants, mean age 71.4 years, and 51.6% were female.

From 2005-2006 to 2010-2011, a slight increase in the use of at least 1 prescription medication was seen (84.1% to 87.7%; P = .003). An increase in concurrent use of at least 5 prescription medications was also seen between the 2 groups (30.6% to 35.8%; P = .02).

OTC medication use in the 2 groups showed a decline, from 44.4% in 2005-2006 to 37.9% in 2010-2011, whereas the use of dietary supplements increased, from 51.8% to 63.7% (P < .001 for both), respectively.

Clinically significant increases in the use of certain types of drugs from 2005-2006 to 2010-2011 were seen for statins (33.8% to 46.2%), antiplatelets (32.8% to 43.0%), and omega-3 fish oils (4.7% to 18.6%) (P < .05 for all).

Potential for major drug-drug interaction among older adults also increased from 2005-2006 to 2010-2011, from 8.4% to approximately 15.1%, respectively, (P < .001), mostly due to increases in the use of medications and dietary supplements in the second cohort.


1. Qato DM, Wilder J, Schumm LP, Gillet V, Alexander GC. Changes in prescription and over-the-counter medication and dietary supplement use among older adults in the United States, 2005 vs 2011 [published online ahead of print March 21, 2016]. JAMA Intern Med. doi:10.1001/jamainternmed.2015.8581.