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Are there any drug interactions with tamoxifen?

Tamoxifen (brand name Nolvadex is no longer available by the manufacturer) is a medicine to treat estrogen-sensitive breast cancer. In some cases, it's prescribed to prevent breast cancer. The drug works by blocking the effects of estrogen in the breast tissue and slowing tumor growth.

People who took tamoxifen along with a certain combination of chemotherapy agents—cyclophosphamide and fluorouracil with methotrexate—were more likely to get blood clots than those who didn't take tamoxifen. Tamoxifen can increase the actions of a blood-thinning drug called warfarin (Coumadin), which can make bleeding more likely. If you take these medicines with tamoxifen, your doctor should carefully monitor your condition.

Sources:
Drug Facts and Comparisons, Facts & Comparisons, 2006.
Hansten PD, Horn JR. Drug Interactions Analysis and Management, Applied Therapeutics, 1999.
Micromedex® Healthcare Series. Thomson Micromedex, 2006.
Nolvadex Product Information. Zeneca Pharmaceuticals, 2006.

This answer prepared 5/21/2000.
This information updated 12/01/2006.