Grant: Canada Postdoctoral Research Award (CPRA) program

Medications are part of daily life for millions of Canadians. When medications are taken in combination, one drug may influence the effect of another, at times leading to serious harm or even death. Such "drug-drug interactions" (DDIs) can be especially dangerous for older adults, who often take multiple medications each day and have health conditions that make them more vulnerable to harm. Pharmacists play a role in preventing DDIs, but in Ontario and many other provinces, their efforts are limited because pharmacies do not share prescription claims data. To date, no study has examined whether filling prescriptions at multiple pharmacies increases the risk of harm resulting from a DDI. I propose a series of studies to examine whether, among older people taking medications prone to drug interactions, filling other prescriptions at a different pharmacy increases the risk of hospitalization for drug toxicity. The project will use data on hospital admissions, emergency visits, and prescriptions from community pharmacies among Ontarians aged 66 years and older who experienced drug-related harm. We will then repeat the study in British Columbia, where pharmacists have had real-time access to province-wide prescription claims data across all community pharmacies for decades. I anticipate that in Ontario, patients who fill a DDI-triggering medication and subsequently experience drug-related toxicity are more likely to receive it from a pharmacy different from the one where they usually fill their other prescriptions, and that this association will be weaker in British Columbia. If confirmed, these findings will underscore the importance of sharing real-time prescription data across pharmacies and support the modernization of pharmacy software to prevent harmful drug interactions before they occur.