Increase effects of anticoagulant. May increase phenytoin levels. Enhanced metabolism w/ carbamazepine & phenytoin. Increase metabolism & excretion w/ rifampicin & barbiturates. Cardiac glycosides. Enhanced effects of sympathomimetic agents. Accelerated TCA response. Decreased absorption w/ cholestyramine; Ca- , Al-, Mg-, Fe supplements, Al hydroxide, polystyrene sulfonates, sucralfate, lanthanum, bile acid sequestrants (eg, colestipol), anion/cation exchange resins (eg, kayexalate, sevelamer), Ca carbonate & ferrous sulphate; proton pump inhibitors. Decreased intestinal absorption w/ soy-containing compd & high fibre diets. OCs; other drugs, including estrogen, tamoxifene, clofibrate, methadone & 5-flurouracil; HMG-CoA reductase inhibitors (statins); drugs that may decrease serum conc of thyroxine-binding globulin, including androgens & anabolic steroids; tyrosine kinase inhibitors (eg, imatinib & sunitinib); propranolol, amiodarone, lithium, iodide, oral contrast agents, propylthiouracil, glucocorticoids, sertraline; insulin or oral antidiabetics, phenylbutazone or acetylsalicylic acid