If you are being treated with any of the following medications, you should not use selenium supplements without first talking to your health care provider.

Drugs that affect selenium levels in the body -- These drugs may lower levels of selenium:

• Cisplatin, a chemotherapy drug
• Clozapine (Clozaril)
• Corticosteroids, such as prednisone
• Valproic acid (Depakote)

Anticoagulants and antiplatelet drugs (blood thinners) -- When combined with these drugs, selenium may increase the risk of bleeding:

• Clopidogrel (Plavix)
• Warfarin (Coumadin)
• Heparin
• Aspirin

Barbiturates -- In animal tests, selenium seems to make the sedative effects of these drugs last longer:

• Butabarbital (Butisol)
• Mephabarbital (Mebaral)
• Phenobarbital (Nembutal)
• Secobarbital (Seconal)

Chemotherapy -- Although selenium may help reduce side effects from drugs such as cisplatin, doxorubicin, and belomycin, it may also interfere with their cancer-fighting ability. If you are undergoing chemotherapy, talk to your oncologist before taking selenium or any other supplement.

Cholesterol-lowering medications -- Simvastatin (Zocor) and niacin have been shown to lower LDL ("bad") cholesterol and raise HDL ("good") cholesterol in people with heart disease. Taking antioxidants, including selenium, along with these drugs may reduce their effectiveness. Theoretically, selenium may also reduce the effectiveness of other statins, including atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), and prevastatin (Pravachol).