Decreased absorption w/ cholestyramine, Ca-, Al-, Mg- & Fe supplements, polystyrene sulfonates, sucralfate, lanthanum, bile acid sequestrants (eg, colestipol), anion/cation exchange resins (eg, kayexalate, sevelamer), proton-pump inhibitors; wt loss drugs eg, orlistat. Decreased intestinal absorption w/ soy-containing compds, high-fibre diets. Enhanced metabolism w/ anticonvulsants eg, carbamazepine, phenytoin. Increased metabolism w/ enzyme inducers ie, rifampicin, barbiturates. Lowered therapeutic effect by propranolol, amiodarone,
lithium, iodide, oral contrast agents, propylthiouracil, glucocorticoids. Increased dosage requirements in hypothyroid patients w/ tyrosine kinase inhibitors eg, imatinib, sunitinib. Reduced serum levels w/ sertraline. Increased dosage requirements w/ OCs, tamoxifene, clofibrate, methadone, 5-fluorouracil. Increased thyroid hormone requirements w/ HMG-CoA reductase inhibitors eg, simvastatin, lovastatin. Increased need for insulin or oral antidiabetics in patients w/ diabetes. Increased effect of anticoagulants. Increased phenytoin levels. Increased receptor sensitivity to catecholamines. Accelerated response to TCAs. Enhanced effects of sympathomimetic agents. Potential interaction w/ ritonavir-containing products. Decreased dosage requirements w/ androgens, anabolic steroids. False low plasma conc w/ anti-inflammatory treatment eg, phenylbutazone or acetylsalicylic acid.