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Some Antidepressants Reduces Effectiveness of Tamoxifen for Breast Cancer

Some Antidepressants Reduces Effectiveness of Tamoxifen for Breast CancerA new study suggests that women who take antidepressants such as Prozac, Zoloft or Paxil may be impacting the effectiveness of the breast cancer prevention drug, tamoxifen. Such an effect likely increases a woman’s risk of the cancer returning in the future.

Researchers found that using a combination of depression medicines and cancer prevention drug can virtually wipe out the benefit tamoxifen provides to women who take it to prevent the return of breast cancer. Many of the same women also take antidepressants for hot flashes, because hormone pills aren’t considered safe after breast cancer.

Tamoxifen is an estrogen suppressor which helps lower the risk that breast cancer will return and improves survival rates. The drug that cuts in half the chances of a breast cancer recurrence is consumed by nearly 500,000 women in the United States.

The novel study now shows that antidepressants like Paxil, Prozac and Zoloft, which are considered moderate-to-potent CYP2D6 inhibitors, interfere with the active ingredient in tamoxifen, which can double a woman’s risk of having her cancer return.

Researchers from Medco Health Solutions Inc. and the Indiana University School of Medicine presented their findings Saturday at a meeting of the American Society of Clinical Oncology in Orlando.

“We’ve known that these CYP2D6 inhibitor drugs block the activation of tamoxifen chemically, but this is the first time there’s evidence that these drugs are putting women at a much higher risk for recurrent breast cancer,” said Robert Epstein, Medco Health Solutions’ chief medical officer and one of the study authors.

To reach their findings, Epstein and colleagues studied about 1,300 women who were newly prescribed tamoxifen to treat breast cancer between 2003 and 2005. The team monitored the women for at least two years.

The research investigators assigned 353 women to take strong CYP2D6 inhibitor drugs such as Paxil, Prozac or Zoloft along with the tamoxifen, and 945 women to use tamoxifen only.

After comparing the two groups, the researchers found that women taking a combo of the CYP2D6 inhibitors and tamoxifen were 13.9% more likely to have their breast cancer tumors back compared to 7.5% of those taking just tamoxifen.

Not all antidepressants pose this problem so women should talk to their doctors about which ones are best. Never stop taking a medication without first consulting your doctor.

Breast cancer is caused by the development of malignant cells in the breast. After skin cancer, it is the second most common cancer in women.

According to the Atlanta-based U.S. Centers for Disease Control and Prevention estimates, about 187,000 women were diagnosed with breast cancer and 41,000 women died from the disease in 2005 (the most recent year for which CDC data are available).

Source: American Society of Clinical Oncology

Some Antidepressants Reduces Effectiveness of Tamoxifen for Breast Cancer

Psych Central News Editor

APA Reference
News Editor, P. (2018). Some Antidepressants Reduces Effectiveness of Tamoxifen for Breast Cancer. Psych Central. Retrieved on March 24, 2019, from
Scientifically Reviewed
Last updated: 8 Aug 2018
Last reviewed: By a member of our scientific advisory board on 8 Aug 2018
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