The elimination of Warfarin is almost entirely by metabolism. Warfarin is stereoselectively metabolized by hepatic cytochrome P-450 (CYP450) microsomal enzymes to inactive hydroxylated metabolites (predominant route) and by reductases to reduced metabolites (Warfarin alcohols) with minimal anticoagulant activity. Identified metabolites of Warfarin include dehydroWarfarin, two diastereoisomer alcohols, and 4′-, 6-, 7-, 8-, and 10- hydroxyWarfarin. The CYP450 isozymes involved in the metabolism of Warfarin include CYP2C9, 2C19, 2C8, 2C18, 1A2, and 3A4. CYP2C9, a polymorphic enzyme, is likely to be the principal form of human liver CYP450 that modulates the in vivo anticoagulant activity of Warfarin. Patients with one or more variant CYP2C9 alleles have decreased S-Warfarin clearance [see Clinical Pharmacology ( )] .
Anticoagulants: Patients on anticoagulants such as warfarin should be carefully monitored during anabolic steroid therapy as anabolic steroids may increase sensitivity to oral anticoagulants which may require a concomitant reduction in anticoagulant dosage to achieve a desirable prothrombin time (PT). Anticoagulant patients should be monitored regularly during anabolic steroid therapy, particularly during initiation and termination of therapy. Warfarin patients should have INR and PT monitored throughout androgen therapy and warfarin dosages titrated to achieve the desired INR and PT. Such patients should be monitored for occult bleeding.
In July 2011, FDA began a pilot program to notify people of drug recalls before they are classified in an effort to expedite notifications of human drug product recalls to the public. FDA is now able to accomplish the goal of expedited notification within the Enforcement Report. These recalls are identified within the Enforcement Report by the label of “Not Yet Classified” in the “Classification” column. It is also possible to search the Enforcement Report for these “Not Yet Classified” recalls using the filter drop down menu. Therefore, as of September 15, 2017 FDA will discontinue the pilot program, and will no longer post drug recalls that are pending classification on this webpage. To see posted recalls that are pending classification go to the weekly Enforcement Report.