Seniors bear the brunt of the problem. For those over 65, the likelihood of an ER visit due to drug reactions was twice that of younger people. They were seven times as likely to be admitted to the hospital for treatment following such an incident, the study found.

The worst offenders were the blood-thinner warfarin, the diabetes drug insulin and the heart medicine digoxin, the researchers reported. Negative effects related to their use caused a third of ER visits by people over 65.

Amoxicillin, aspirin and trimethoprimsulfamethoxazole, an antibiotic, were also among the drugs most often responsible for ER visits due to negative reactions.