Nearly half (48 percent) of the 100,000 hospitalizations occurred among adults 80 and up, according to the study, published in the Nov. 24 issue of the New England Journal of Medicine. Nearly two-thirds (66 percent) were the result of unintentional overdoses.
The four medications, used alone or together, most often cited:
The blood thinning medication warfarin (Coumadin, Jantoven), which is used to treat blood clots, was involved in 33 percent of emergency hospitalizations.
Insulin, used to control blood sugar in diabetes patients, was involved in 14 percent of cases.
Antiplatelet drugs such as aspirin and clopidogrel (Plavix), which are used to prevent blood clots, were involved in 13 percent of cases.
Oral hypoglycemic agents -- diabetes medications taken by mouth -- were involved in 11 percent of cases.
With antiplatelet or blood thinning drugs, bleeding was the main problem. For insulin and other diabetes medications, about two-thirds of cases involved changes in mental status such as confusion, loss of consciousness or seizures.