Tamoxifen and Antidepressants Don't Mix

Benefits of the lifesaving breast cancer drug may be negated by certain antidepressants.

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Breast cancer patients have it tough. Besides contending with the disease and its often harrowing treatments, they're also told to avoid certain medications—like hormone therapy for menopausal symptoms—because it could raise their likelihood of having a recurrence. In fact, many breast cancer patients are prescribed antidepressants to combat the hot flashes and mood swings of menopause. Or they're taking the drugs to cope with chronic depression. Unfortunately, these very same mood-lifters also appear to negate the effects of tamoxifen, a lifesaving breast cancer therapy given to women who have tumors that respond to estrogen.

Research presented Sunday at the American Society of Clinical Oncology finds that breast cancer patients taking antidepressants along with tamoxifen were more than twice as likely to have their tumors return after two years, compared with those who were taking tamoxifen alone. The Food and Drug Administration is poised to add a warning to tamoxifen's label alerting doctors to the drug's interaction with antidepressants, according to the Wall Street Journal.

But doctors who are up to date on the latest medical research should already know about this interaction. As early as six years ago, research indicated that tamoxifen was rendered ineffective by antidepressants in the family of selective serotonin reuptake inhibitors (Paxil, Prozac, Celexa, Lexapro, Zoloft). In 2005, oncology researcher Frankie Ann Holmes lamented in a paper published in the Journal of Oncology Practice that doctors still were prescribing Prozac with tamoxifen. "Conversations with colleagues," Holmes wrote, "indicated that this more sophisticated understanding of the peculiar pharmacokinetics of tamoxifen may not have been incorporated into clinical patient care, especially when patients receive medications from other non-oncology physicians."

I'm just wondering what's taken the FDA so long. Why wasn't the tamoxifen label changed years ago?

Breast cancer patients who are on tamoxifen have several options. Postmenopausal women can switch to an aromatase inhibitor, which has the same estrogen-blocking benefits as tamoxifen but doesn't interact with antidepressants. (Aromatase inhibitors aren't approved for use in premenopausal patients.) Women of any age can also switch to a non-SSRI antidepressant like Effexor. Those who aren't putting themselves at risk for a relapse of depression—check with your doctor before stopping an antidepressant—can also try to lift their mood using lifestyle measures like exercise, adequate sunlight, and fish oil. Here are some natural ways to treat depression and what to take for tamoxifen-triggered hot flashes.