Potentially inappropriate prescribing in Ontario community-dwelling older adults and nursing home residents

OBJECTIVES: To compare patterns of potentially inappropriate drug therapy prescribing in community-dwelling older adults and nursing home residents in Ontario, Canada. DESIGN: A retrospective cohort study using administrative databases. SETTING: Ontario community and nursing home facilities. PARTICIPANTS: All 1,275,619 older adults aged 66 and older in Ontario (1,216,900 community-dwelling and 58,719 nursing home residents) who were dispensed at least one prescription from the comprehensive provincial drug plan in 2001. In Ontario, the provision of clinical pharmacy services is mandated in the nursing home setting. No comparable program exists for older adults in the community setting. MEASUREMENTS: Potentially inappropriate drug prescribing was compared between community-dwelling and nursing home residents in two categories: those to always avoid and therapies considered rarely appropriate to prescribe. RESULTS: Of the 1,275,619 adults in the cohort, nursing home residents were older (mean age+/-standard deviation=84.2+/-7.6 vs 75.0+/-6.5, P<.001), included more women (73.3% vs 57.7%, P<.001), had higher comorbidity scores (measured by the number of distinct drug therapies dispensed in the prior year (10.7+/-6.8 vs 7.2+/-5.7, P<.001) and Charlson comorbidity scores (1.4+/-1.6 vs 0.9+/-1.5, P<.001)) than community-dwelling individuals. Community-dwelling older adults were significantly more likely to be dispensed at least one drug therapy in the always avoid or rarely appropriate category than nursing home residents (3.3% vs 2.3%, P<.001). Using a logistic regression model that controlled for age, sex, and comorbidity (number of distinct drug therapies dispensed in the prior year), nursing home residents were close to half as likely to be dispensed one of these potentially inappropriate drug therapies as community-dwelling older adults (odds ratio=0.52, 95% confidence interval=0.49-0.55, P<.001). CONCLUSION: Potentially inappropriate drug therapy in the always avoid and rarely indicated categories is dispensed less often to nursing home residents than to older community-dwelling adults. Clinical pharmacist services, which are mandated in the nursing home setting, may be responsible for these differences in Ontario, Canada.