Atlanta—Dangerous reactions to prescribed medications send 4 out of a 1,000 Americans to emergency departments (EDs), and a growing percentage of them are older adults, according to a new study.

The report, published in the Journal of the American Medical Association, notes that an estimated 35% of ED visits for adverse drug events occurred among adults ages 65 years or older in 2013-2014, compared to about 26% in 2005-2006.

Hospitalization rates for older adults also were the highest, at 44%, according to the CDC-led study. Furthermore, just three drug classes—anticoagulants, diabetes agents, and opioid analgesics—were the culprits in 60% of the cases involving older patients.

That includes four anticoagulants—warfarin, rivaroxaban, dabigatran, and enoxaparin—five diabetes agents, including insulin, and four oral medications—metformin, glipizide, glyburide, and glimepiride—which were among the 15 most common drugs implicated.

Study results also find that 1.18% of the ED visits by older patients involved drugs they never should have been prescribed in the first place, based on Beers criteria.

Overall, the prevalence of ED for adverse drug events in the United States was estimated to be 4 per 1,000 individuals in 2013 and 2014, with 27% resulting in hospitalization.

For the study, CDC researchers examined characteristics of ED visits for adverse drug events in the U.S. in 2013-2014 and changes in ED visits for adverse drug events since 2005-2006, focusing on 58 facilities that participated in the National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance project.

Anticoagulants, antibiotics, and diabetes agents were involved in about 47% of ED visits for adverse-drug events, which included clinically significant adverse events such as hemorrhage caused by anticoagulants, moderate-to-severe allergic reactions from antibiotics, and hypoglycemia with moderate-to-severe neurological effects from antidiabetes agents.

Since 2005-2006, study authors point out, the proportions of ED visits for adverse drug events from anticoagulants and diabetes agents have increased. Fewer patients are seeking emergency care for problems with antibiotics, however.

Specifically for children 5 or younger, antibiotics remain the most common drug class sending them to the ED, accounting for 56% of all cases. Antibiotics also were the most common drug class implicated in ED visits for children and adolescents 6 to 19, accounting for 32%, followed by antipsychotics, at 4.5%.

“Targeting adverse drug events common among specific patient populations, such as among the youngest (age 19 years or less) and oldest (age 65 years and older), may help further focus outpatient medication safety efforts,” the authors conclude.

An accompanying editorial calls for collaboration “among physicians and other health professionals in primary care, specialty care, pharmacy, and emergency medicine to answer these questions in the quest for safer models of patient care. Furthermore, this collaboration across healthcare locations and the continuum of care will affect how much benefit or harm patients receive from prescribed medications. Integrated health care systems can help lead the way through improved care coordination and transition of care models.”

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