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9/19/2000

Nursing Homes May Have 350,000 Adverse Drug Events Annually, Investigators Suggest

Nancy Tarleton Landis

The findings of a study of adverse drug events (ADEs) in Massachusetts nursing homes suggest that 24 ADEs and 8 potential ADEs could be identified annually at the average U.S. nursing home, according to the authors.1 This means that in the 1.55 million residents of U.S. nursing homes, 350,000 ADEs—more than half of them preventable—occur each year. Further, nearly 20,000 fatal or life-threatening ADEs occur, 80% of which are preventable.

Possible drug-related incidents at 18 nursing homes with more than 50 beds each were identified through chart review by two nurses and one pharmacist and through reports by nursing home staff. The incidents were reviewed independently by two physicians to determine the presence of an ADE or potential ADE, whether the event was preventable, and the event's severity and effects on the resident. 

ADEs included adverse reactions not associated with medication errors, as well as those resulting from errors. Potential ADEs were defined as errors that had the capacity to cause injury but failed to do so either by chance or because they were intercepted; all potential ADEs were considered preventable. ADEs were considered preventable if they were due to an error and were preventable by any means available. 

In the 2916 nursing home residents studied for a total of 28,839 resident-months, 546 ADEs and 188 potential ADEs were found. About half of the ADEs (276) were considered preventable. The authors calculated an ADE rate of 1.89 per 100 resident-months and a preventable ADE rate of 0.96 per resident-month. Nursing home staff reported 17% of the ADEs and 4% of the potential ADEs; the rest were identified through review of records. 

The one fatal ADE (methotrexate-induced hepatotoxicity) was categorized as preventable. Of a total of 238 fatal, life-threatening, or serious ADEs, 72% were considered preventable. Of the potential ADEs, 88% were considered life-threatening or serious, compared with 44% of the ADEs. 

Only 17% of the ADEs were associated with symptoms lasting one day or more. Residents suffered disability (decrease in functional status) from 38 events—permanent disability in 8 cases. 

Of the 464 preventable events (276 ADEs plus 188 potential ADEs), most errors occurred at the ordering and monitoring stages. Of 315 errors in ordering, wrong dose was the reason for 200 and well-established, clinically important drug interactions for 68. Of 325 monitoring errors, 133 involved failure to act on available laboratory or clinical findings and 83 involved inadequate laboratory monitoring. 

The drug categories most often associated with preventable ADEs were psychoactive agents and anticoagulants. Nearly 80% of the potential ADEs involved warfarin. 

For preventing ADEs in nursing homes, the authors suggested that computerized systems focusing on ordering and monitoring be designed. 


1Gurwitz JH, Field TS, Avorn J et al. Incidence and preventability of adverse drug events in nursing homes. Am J Med. 2000; 109:87-94.