Older Americans face a greater risk of harmful reactions to medications than younger individuals, a new study suggests.

The study, conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA), found adults ages 50 and older comprised 51.5 percent of all emergency department visits in 2008 that were due to reactions to medications . That's about 1.1 million visits. And of those visits, about 61 percent were made by people aged 65 or older, and 60.9 percent were made by women.

Older people may be more likely to react badly to their medications because of physiological changes that occur with age, or because they're taking multiple medications, the researchers said. These reactions may pose an increasing public health challenge as the number of older Americans continues to grow in decades to come.

"Individuals taking medications need to take personal responsibility, and not assume that just because the medications are legally prescribed that they are without risk," said SAMHSA Administrator Pamela S. Hyde. "People should monitor how they feel when on medication, ask their doctor about what signs to look out for, and not hesitate to contact a doctor if they feel the medication is having adverse effects on their health."

Most of the emergency visits involved reactions to just one medication. Reactions to pain relievers accounted for the largest share of these visits (24.3 percent). Other cases involved cardiovascular system medications, metabolic disorder treatments and psychotherapeutic drugs .

Nearly 33 percent of emergency room visits by older adults resulted in hospitalizations for further treatment, the study showed.

The study was based on data from SAMHSA's 2008 Drug Abuse Warning Network (DAWN). DAWN is a public health surveillance system that monitors drug-related hospital emergency department visits reported throughout the nation.

Pass it on: Older Americans make up the majority of those who visit the emergency room for adverse reactions to medication.

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