warfarin and Androgel 5 g packet Interactions

Interactions between warfarin and Androgel 5 g packet (testosterone)

warfarin and testosterone (Major Drug-Drug)

MONITOR CLOSELY: Androgens and anabolic steroids may potentiate the hypoprothrombinemic response to oral anticoagulants and increase the risk of bleeding. The onset of interaction is generally observed within 2 to 3 days. The mechanism is unknown. There have been case reports of patients stabilized on oral anticoagulant therapy who developed bleeding complications following the addition of various androgenic agents including danazol, oxymetholone, testosterone, methyltestosterone, and stanozolol. In a clinical study (n=15), the concomitant administration of oxandrolone 10 to 20 mg per day increased the half-life of the more active S(-) enantiomer of warfarin from 26 to 48 hours and the systemic exposure (AUC) from 4.55 to 12.08 ng-hr/mL. R(-) warfarin half-life and AUC also increased. Microscopic hematuria and gingival bleeding were reported, and the warfarin dose had to be reduced by 80% to 85% to maintain the desired INR.

MANAGEMENT: During concomitant therapy, the INR and/or PT should be monitored closely and anticoagulant dosage adjusted accordingly, particularly following initiation, discontinuation or change of dosage of the androgenic agent in patients who are stabilized on their anticoagulation regimen. Significant anticoagulant dose reductions may be required. Some experts recommend avoiding this combination altogether. Patients should be advised to promptly report any signs of bleeding to their physician, including pain, swelling, headache, dizziness, weakness, prolonged bleeding from cuts, increased menstrual flow, vaginal bleeding, nosebleeds, bleeding of gums from brushing, unusual bleeding or bruising, red or brown urine, or red or black stools.