Phenprocoumon, hyperglycemic agents (eg, thiazides & corticosteroids), alcohol, furosemide, nifedipine & cationic drugs (eg, amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, cimetidine & vancomycin). Reduced absorption w/ acarbose & guar gum.