A 33-year-old woman with a history of deep vein thrombosis (DVT) presents for follow-up while taking warfarin for anticoagulation therapy. During the visit, she mentions recently starting combination oral contraceptives (COCs) for contraception and menstrual cycle regulation. Her other medications include allopurinol, cimetidine, erythromycin and glipizide. On further discussion, it is noted that she was not aware of the potential interactions between warfarin and her current medications. You decide to counsel her on how her medications alter warfarin requirements. Which of the following medications lead to decreased anticoagulant effect of warfarin?
