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Ontario Drug Benefit plan allows for potentially inappropriate drugs to be prescribed to seniors


Tens of thousands of Ontario seniors who received their medications from the Ontario Drug Benefit (ODB) plan formulary were prescribed potentially inappropriate drug therapies for older adults, a new study from the Institute for Clinical Evaluative Sciences (ICES) shows.

Researchers used a previously developed criterion that identifies 33 drug therapies that should always be avoided, are rarely appropriate, and have some indication, but are often misused in older adults. They compared the patterns of potentially inappropriate drug prescribing between the 1,088,680 community-dwelling Ontario seniors 66 years of age or older using the ODB drug plan formulary in 1996 and a sample of 2,455 community-dwelling older adults in the United States during the same year.


  • Despite existing formulary restrictions in Ontario in 1996:
    • Over 30,000 older adults in Ontario were dispensed at least one drug therapy in the always avoid category;
    • Over 60,000 elderly patients were dispensed a drug therapy in the rarely indicated category; and
    • Over 120,000 were dispensed a therapy in the some indication, but often misused category.
  • Among the 33 potentially inappropriate drug therapies available in the U.S., 45% were not available through the ODB in Ontario in 1996.
  • If Ontario’s drug formulary was applied to the U.S., it may have avoided the use of over one-third of the potentially inappropriate drug therapies.

“Although this study was done in 1996, of the 10 drug therapies in the always avoid or rarely appropriate categories, five remain in the 2003 ODB formulary as a full benefit and one is available as limited use and can be obtained with a written request,” said lead author Dr. Paula Rochon, an ICES scientist and scientist in the Kunin-Lunenfeld Applied Research Unit at the Baycrest Centre for Geriatric Care.

“This suggests that, although many of the potentially inappropriate drug therapies that are available in the U.S. are unavailable from Ontario’s drug formulary, there is likely still considerable room for prescribing these potentially inappropriate medications.”

Dr. Rochon believes that formulary restrictions alone may not be sufficient to improve prescribing. She points to several strategies that should complement formulary restrictions in order to improve the quality of medication use by older adults.

“First, include older and often frailer individuals in clinical trials to increase our understanding of optimal drug therapy in older adults. Second, test and implement technological strategies such as computerized physician order entry systems to reduce drug related adverse events that can be prevented. Third, promote collaboration between physicians and clinical pharmacists, the latter of which are experts in drug prescribing,” said Dr. Rochon.

The study, “Potentially inappropriate prescribing in Canada relative to the United States”, is in the December issue of the journal Drugs and Aging.

Author affiliations: ICES (Drs. Rochon, Bronskill, Anderson, Mamdani, and Ms. Sykora); Kunin-Lunenfeld Applied Research Unit, Baycrest Centre for Geriatric Care (Dr. Rochon); Department of Medicine (Dr. Dhalla and Mr. Lane), Health Policy, Management and Evaluation (Drs. Bronskill and Anderson), and Faculty of Pharmacy (Dr. Mamdani), University of Toronto; Meyers Primary Care Institute, Fallon Healthcare System and University of Massachusetts Medical School (Dr. Gurwitz).

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.


  • Julie Argles
  • Media Relations Officer, ICES
  • (416) 480-4780 or cell (416) 432-8143


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