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Trends in Hospital Visits for Generic and Brand-Name Warfarin Users in Québec, Canada: A Population-Based Time Series Analysis



Federal standards authorize the commercialization of generic medicines after bioequivalence versus the brand-name originator has been demonstrated. For drugs with narrow therapeutic indexes, such as warfarin, the accepted difference in bioavailability is ≤ 10%. No systematic pharmacovigilance studies are conducted once generics become available.


We aimed to assess the impact of the arrival of generic warfarin on hospital visit trends (hospital admissions or emergency room consultations) in warfarin users.


This was an observational interrupted time series analysis (2 January 1996 to 1 January 2016). Using the Québec Integrated Chronic Disease Surveillance System, we included all patients who were aged ≥ 66 years, publicly covered and using brand-name or generic warfarin (N = 280,158). We estimated rates of hospital visits in 6-month periods, 5 years before and up to 15 years after the arrival of generic warfarin. Periods before and after were compared using segmented regression models for all users along with exploratory (generic vs. brand name)/subgroup analyses (cardiovascular comorbidities and socioeconomic status).


Generic warfarin arrived on the market on 2 January 2001. Over the 20-year period of the study, the mean rate of hospital visits was 113 for 100 brand-name or generic users per 6-month period and was similar before and after the arrival of the generics. Up to 15 years after the arrival of the generics, the rates of hospital visits were 10% higher for generic than for brand-name users, which was confirmed by subgroup analyses.


Overall, we observed no impact on hospital visits after the arrival of generic warfarin in all the population treated with any type of warfarin. However, a higher crude rate of hospital visits among generic users than brand-name users remains to be validated using a different methodology and specific outcomes.

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The authors are grateful to the INSPQ, the ministry of health and social services and the Régie de l’assurance maladie du Québec (RAMQ) for providing the data used as part of the provincial’s government plan for continuous chronic disease surveillance mandate.

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Correspondence to Paul Poirier.

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Conflict of interest

Paul Poirier has received honoraria for continuing medical education/consultants/experts events from Abbott Vascular, Amgen, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Eli Lilly, Janssen, Merck, Novartis, Novo Nordisk, Pfizer, Roche, Sanofi-Aventis, Servier, and Valeant. Jacinthe Leclerc, Claudia Blais, Louis Rochette, Denis Hamel and Line Guénette have no potential conflicts of interest that might be relevant to the contents of this manuscript.


No external funding was used in the preparation of this manuscript as it was part of the continuous chronic disease surveillance mandate in Québec, Canada. Jacinthe Leclerc was the recipient of two PhD studentships during this project: (1) from the Fondation de l’Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval and (2) from the Société Québécoise d’insuffisance cardiaque, alliance BMS-Pfizer. Line Guénette holds a Junior-1 clinical researcher salary award from the FRQ-S in partnership with the Société québécoise d’hypertension artérielle. Paul Poirier is a senior clinical researcher of the Fonds de recherche du Québec-Santé (FRQ-S).

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Leclerc, J., Blais, C., Rochette, L. et al. Trends in Hospital Visits for Generic and Brand-Name Warfarin Users in Québec, Canada: A Population-Based Time Series Analysis. Am J Cardiovasc Drugs 19, 287–297 (2019).

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