A new analysis suggests that substitution of generic warfarin for brand-name warfarin (Coumadin, Bristol-Myers Squibb) has no appreciable effect on rates of international normalized ratio (INR) testing or hospitalization for adverse events. A recent Canadian publication examined the effects of a mandated switch to the generic product in 2001. The authors examined all warfarin prescriptions in the 40 months before the policy was put in place, during the month in which the policy came into effect, and in the 9 months after the implementation of the policy. They also checked for drugs that might affect outcomes in patients also taking warfarin.

After the switch to generic warfarin, the authors saw no change in rates of INR testing or in hospitalizations for major hemorrhage or cerebral thromboembolism, even after adjusting for use of other drugs that affect coagulation. These results may help overcome lingering fears on the part of health care professionals who still have concerns about switching narrow therapeutic index drugs to generic products.

Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.