An interaction between danazol and warfarin in women with menorrhagia treated for thinning the endometrium prior to resection

Six patients on long‐term anticoagulant therapy with warfarin, and suffering from menorrhagia, underwent hysteroscopic endomyometrial resection. They received 600 mg danazol daily preoperatively for 4 weeks to suppress the endometrium. The simultaneous use of danazol and warfarin potentiated the anticoagulation effect of warfarin, the mean reduction of warfarin dosage being 52%. Three patients out of six experienced bleeding complications because of increased anticoagulation, two of them postoperatively. One patient experienced excessive bleeding after having danazol continued postoperatively. Patients on warfarin therapy who are prescribed danazol must be monitored closely to avoid excessive anticoagulation and subsequent bleeding in hysteroscopic surgery. Concomitant use of these drugs postoperatively must be avoided.