Treatment of breast cancer

Published: 2010-06-30

Drugs that should be avoided by women who are taking tamoxifen for the prevention of breast cancer, either primary or recurrence, are listed in a review published online in the J Clin Oncol. 2010 Jun 1;28(16):2768-76. [1].

The clinical benefit of tamoxifen is related to the functional status of the hepatic metabolizing enzyme cytochrome P450 2D6 (CYP2D6). CYP2D6 is the key enzyme responsible for generating the potent tamoxifen metabolite, endoxifen. Most studies show that women with impaired CYP2D6 metabolism have lower endoxifen concentrations and a greater risk of breast cancer recurrence. As a result, practitioners must be aware that some of the most commonly prescribed drugs co-administered with tamoxifen interfere with CYP2D6 function, thereby reducing endoxifen concentrations and potentially increasing the risk of breast cancer recurrence. The review provides a guide for the use of medications that inhibit CYP2D6 in patients given tamoxifen.

1. www.ncbi.nlm.nih.gov/pubmed/20439629