At the recent annual meeting of the American Society of Clinical Oncology, research was presented about a serious interaction between tamoxifen, a breast cancer drug, and some antidepressants such as Paxil, Prozac and Zoloft. According to the study, women who used both drugs had twice the risk of their cancer returning. However, the same interaction was not seen when other antidepressants such as Celexa, Lexapro, and Luvox were taken with tamoxifen.
Tamoxifen is used to prevent the recurrence of one of the most common types of breast cancer – tumors that are estrogen-dependent. Earlier laboratory studies had shown that drugs that iinterfere with the enzyme CYP2D6, also block tamoxifen activation. Drugs like Paxil and Prozac are known as moderate-to-potent CYP2D6 inhibitors. The FDA plans to warn doctors about the tamoxifen/antidepressant interaction, now that it has evidence about clinical outcomes. It is likely that new warnings will be placed on the tamoxifen label.