PUBLIC HEALTH SURVEILLANCE REVEALS AN INCREASE IN HEALTH CARE UTILIZATION FOR GENERIC VS. BRAND-NAME WARFARIN USERS

Abstract

Even with nowadays many direct oral anticoagulant options, brand-name or generic warfarin is still widely used to prevent atherothrombotic events in cardiology. Federal standards regulate bioequivalence of generic vs. brand-name drugs through comparative bioavailability studies but do not regulate clinical equivalence or tolerability in “real-life” settings. Through our public health surveillance system, we have evaluated the impact of the generic warfarin commercialization on health care utilization: emergency room (ER) consultations or hospitalizations. We did an interrupted time series analysis using the Québec Integrated Chronic Disease Surveillance System, a surveillance system of the second most populous province in Canada (∼8.3 million in 2016). Rates of health care utilization for warfarin users (n=280,158) aged ≥ 66 years were calculated for six-month periods, five years before and up to 15 years after warfarin commercialization (from January 1996 to January 2016). Periods before and after generic warfarin commercialization were compared by negative binomial segmented regression models for all users with a specific variable for generic or brand-name users. Sensitivity analyses were also conducted. Generic warfarin analogs were first reimbursed on January 2, 2001. Over the 20-year period, there was a mean rate of 113 ER or hospitalizations for 100 brand-name or generic users per six-month period, similar before and after generics arrival. After onset of generics reimbursement, there was an immediate increase in rates of health care utilization for generic vs. brand-name users (difference-hospitalizations: 8.0% [95% confidence interval: 1.5% to 14.6%]; ER consultations: 9.1% [4.2% to 14.1%]). Rates of health care utilization remained higher for generic vs. brand-name users up to 15 years after generic warfarin reimbursement, with parallel trends for both outcomes (difference: 0.0% [0.0% to 0.1%]). Sensitivity analyses confirmed the results. Among generic warfarin users, we observed increased rates of health care utilization six months after generics commercialization. Risk and survival analysis studies controlling for potential confounders are required to better characterize generic substitution, as stricter licensing process may be required.