The number of older adults using dangerous drug combinations has nearly doubled within a recent 5-year period, according to a study published in JAMA Internal Medicine.

Researchers also observed increases in the rates of polypharmacy and the use of dietary supplements.

The study cohort included 2,351 participants in 2005 to 2006 (mean age, 70.9 years) and 2,206 participants in 2010 to 2011 (mean age, 71.4 years). The investigators analyzed the prevalence of medication use, including concurrent use of prescription and nonprescription medications as well as the type and frequency of major drug interactions.

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The use of over-the-counter medications decreased from 44.4% to 37.9%, but the use of dietary supplements increased significantly, from 51.8% to 63.7%. The rate of polypharmacy increased from 30.6% to 35.8%. The researchers hypothesized that this increase could be due to a number of factors, including the implementation of Medicare Part D, changes in treatment guidelines, and increased availability of generic versions of commonly prescribed medications.

The study identified 15 potentially life-threatening drug combinations of the most commonly used medications and supplements. In 2005, 8% of older adults regularly used at least 1 of these combinations. That percentage increased to 15% in 2011.

In most cases, these dangerous drug combinations involved preventive cardiovascular medications, anti-platelet medications, and supplements. More than half of the dangerous combinations involved a nonprescription medication or dietary supplement.

“Many older patients seeking to improve their cardiovascular health are also regularly using interacting drug combinations that may worsen cardiovascular risk,” said researcher Dima Mazen Qato, PharmD, MPH, PhD, of the University of Illinois at Chicago. “For example, the use of clopidogrel in combination with the proton-pump inhibitor omeprazole, aspirin, or naproxen – all over-the-counter medications – is associated with an increased risk of heart attacks, bleeding complications, or death. However, about 1.8% – or 1 million – older adults regularly use clopidogrel in interacting combinations.”

To help reduce deaths from drug interactions, the researchers recommend that clinicians carefully consider the risks associated with different drug combinations. Clinicians should also counsel older adults about the potential adverse effects of combining medications.


  1. Qato DM, Wilder J, Schumm LP, et al. Changes in prescription and over-the-counter medication and dietary supplement use among older adults in the United States, 2005 vs 2011. JAMA Intern Med. Published online March 21, 2016. doi:10.1001/jamainternmed.2015.8581.