Effects diminished by aminoglutethimide, barbiturates, carbamazepine, griseofulvin, phenobarb, primidone, rifampicin & vit K. Effects enhanced by anabolic steroids, amiodarone, certain antibiotics, cimetidine, clofibrate, danazol, disulfiram, imidazole antifungals, omeprazole, phenytoin, propafenone, tamoxifen & thyroxine.