One in 5 prescription medications taken by seniors are inappropriate (misprescribed, overprescribed or underprescribed), according to a new multi-study analysis.

Many of these inappropriate prescriptions were for drugs considered to be "high risk" for triggering an adverse drug event (ADE)—an injury caused by a prescription medication.

Over 530,000 preventable dangerous drug interactions occur among Medicare beneficiaries each year, according to the Institute of Medicine. Inappropriate prescriptions are one of the primary causes of ADEs in the elderly.

German researchers reviewed 19 separate studies on inappropriate medication prescription in the adults 65 years and older to get a better sense of the impact the problem has on the aging population. They focused only on medications that were prescribed by a senior's primary care physician.

The analysis highlights the need for better prescription management strategies for the elderly, many of whom take between five and twelve different medications to manage several chronic conditions, according to the Centers for Disease Control.

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For tips on how to help a senior keep tabs on their medications, see our Guide for Managing Medications and Prescriptions .