- Warfarin, heparin, thrombin inhibitors, factor Xa inhibitors, and systemic thromobolytics and fibrinolytics. A list of prohibited medications for the flex-sig procedure can be found in the appendix of the MOPS. A bridge course of short-acting low-molecular weight heparin within the 7-day pre-procedure window in patients receiving a chronic systemic anticoagulant who can be safely maintained off anticoagulation for several days is permitted if cleared by the subject's primary healthcare provider and the UHCMC Digestive Health Institute.