Drug interactions between warfarin and sulfonylureas are suggested by pharmacokinetic information and prior studies. However, clinical evidence on the association of such interactions and the risk of bleeding is lacking. Using health care claims data from five US Medicaid programs from 1999-2011 and a self-controlled case series design with warfarin as an object drug, we examined confounder-adjusted rate ratios (RRs) for three outcomes separately: 1) serious bleeding as a composite outcome of gastrointestinal bleeding (GIB) and non-traumatic intracranial hemorrhage (ICH); 2) GIB; and 3) ICH. In 6,463 warfarin users experiencing serious bleeding, an increased risk of serious bleeding was not associated with concomitant use of glimepiride (RR: 0.93; 95% confidence interval: 0.75 to 1.15), glipizide (RR: 0.97; 0.84 to 1.13), glyburide (RR: 0.89; 0.76 to 1.06), or metformin (RR: 0.85; 0.76 to 0.96), nor was the occurrence of the component outcomes of GIB or ICH. These results suggest that use of sulfonylureas or metformin was not associated with an increased rate of serious bleeding in warfarin users.
Clin. Pharmacol. Ther.
Sulfonylureas and metformin were not associated with an increased rate of serious bleeding in warfarin users: a self-controlled case series study.