Chicago—The percentage of older patients using potentially dangerous combinations of prescriptions, OTC medications, and dietary supplements has more than doubled over a 5-year period, according to new research.

The study, published recently in JAMA Internal Medicine, included 2,351 participants in 2005-2006 and 2,206 in 2010-2011, all between the ages of 62 and 85. Unlike past studies using medical records and other compiled data, researchers from the University of Illinois in Chicago used in-home interviews and direct medication inspections to determine which products were being used.

The researchers found that about 15.1% of older adults in 2010-2011 were at risk for a major drug interaction in 2010-2011, compared with an estimated 8.4% in 2005-2006. One example provided by the study team was the concurrent use of preventive cardiovascular medications and supplements.

The study reports increases in:

• Concurrent use of at least five prescription medications from 30.6% to 35.8% over the study period.
• Concurrent use of five or more medications or supplements of any type from 53.4% to 67.1%.
• Dietary supplement use from 51.8% to 63.7%, most often multivitamin or mineral supplements, and calcium.

At the same time, use of OTC medications declined from 44.4% to 37.9%

Study authors suggest that factors that could account for the upsurge include the implementation of Medicare Part D, changes in treatment guidelines, and the increased availability of generics for many commonly used drugs.

Simvastatin, which became available as a generic in 2006, was the most commonly used prescription medication in the older adult population, doubling from 10.3% to 22.5%, said Dima Mazen Qato, PharmD, MPH, PhD, assistant professor of pharmacy systems, outcomes and policy.

The largest increase in dietary supplements, meanwhile, involved omega-3 fish oils. Despite limited evidence of cardiovascular benefits, usage rose from 4.7% of those surveyed in 2005 to 18.6% in 2011.

The report identified 15 potentially life-threatening drug combinations of the most commonly used medications and supplements. More than half of the potential interactions involved a nonprescription medication or dietary supplement, Dr. Qato said, adding that statins and supplements, specifically omega-3 fish oil, were factors in most of them.

“Many older patients seeking to improve their cardiovascular health are also regularly using interacting drug combinations that may worsen cardiovascular risk,” Qato explained. “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 million—older adults regularly use clopidogrel in interacting combinations.”

Study authors urged pharmacists and other healthcare professionals to counsel patients about the risks. “Improving safety in the use of interacting medication combinations has the potential to reduce preventable, potentially fatal, adverse drug events,” Dr. Qato said.

In an invited commentary, Michael A. Steinman, MD, of the University of California, San Francisco and the San Francisco Veterans Affairs Health Care System called for better tracking of medications, a team approach to monitoring medication effectiveness and adverse effects—including pharmacists—and more patient engagement and coaching.

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