Tamoxifen is an important drug to prevent recurrence of breast cancer, but a new study shows it should not be taken in conjunction with certain antidepressants. Roughly 1,300 women were followed for one year. Sixteen percent of those taking antidepressants such as Prozac, Paxil and Zoloft had a recurrence during that time. Those who were not taking antidepressants had a recurrence rate of 7.5 percent.
The scientists have an explanation for why Prozac, Paxil and Zoloft might be interfering with tamoxifen’s effectiveness. The antidepressants inhibit an enzyme (CYP2D6) that activates the anti-cancer drug. Other antidepressants that don’t affect this enzyme would be a much better choice as they appear unlikely to interact with tamoxifen. Such antidepressants include Effexor, Lexapro, Luvox and Celexa. About half a million women in the U.S. take tamoxifen to prevent breast cancer recurrence and about a third of them are prescribed antidepressants. The FDA is considering changing the label to warn doctors about this potentially deadly interaction.