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ICES study shows economic burden associated with adverse drug reactions among elderly in Ontario


A new study by scientists at the Institute for Clinical Evaluative Sciences (ICES) shows that the total annual cost of treating adverse drug reactions (ADRs) in the elderly was over $13.6 million annually in Ontario, and estimated at $35.7 million in Canada.

This is one of the few studies on the overall incidence and costs of ADRs and it suggests that the economic burden associated with ADRs in emergency departments is significant.

The study found a number of important risk factors for experiencing severe ADRs including a recent hospitalization, more prescriptions, use of multiple pharmacies and residing in a long-term care home.

Senior author on the study, Dr. Walter Wodchis, said, “Of these risk factors we are most concerned about the use of multiple pharmacies and the fact that ADRs are most common among residents of long-term care homes.” Wodchis, who is a senior scientist at ICES and a researcher at U of T’s Institute for Health Policy, Management and Evaluation, as well as Toronto Rehab, added, “Simple things such as computerized monitoring programs or consulting programs and medication reconciliation may help for those patients who have multiple and complex drug regimens.”

The rapid rise in the availability and use of pharmaceutical agents, as well as the use of multiple medications at the same time directly increases the risk of patients to developing ADRs.

Any effective drug can cause an ADR even when it is administered properly at the normal dose, but when severe ADRs happen, it raises the question of whether the harm of a drug outweighs the benefit to the patient. And there is a cost to society – individuals identified as having ADRs in the emergency department who were admitted to hospitals incurred costs that were three times higher than for people with ADRs who were discharged home.


  • A retrospective cohort design using population-based healthcare administrative databases
  • Data from April 2003 to March 2008
  • Incidence and costs of ADR-related ED visits and subsequent hospital admissions were estimated for all adults aged 66 years and older

“In spite of the rigour of this study, we believe that we have underestimated the prevalence and magnitude of ADRs by at least a factor of five when we compare our data to prospective studies in Canada and around the world,” said Wodchis. He added that the study used administrative data that may not have accurate coding of ADRs and that some physicians may not be able to recognize ADRs.

Approximately three quarters of one per cent of total annual ED visits among adults aged 66 years and older were found to be ADR-related; and among these patients 21.6 per cent were hospitalized.

The study “Incidence and economic burden of adverse drug reactions among elderly patients in Ontario emergency departments” was published in the September issues of Drug Safety.

Authors: Wu C., Bell CM, Wodchis WP.

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.


Read the Journal Article