Some Antidepressants May Interfere With Breast Cancer Drug, Researchers Say

Certain types of antidepressant drugs may prevent a drug commonly taken to treat breast cancer from working properly, U.S. researchers have found.

In a newly concluded study of the cancer drug tamoxifen and the use of serotonin reuptake inhibitor (SSRI) antidepressants, which include Prozac, Paxil, and Zoloft, the drug combination was found to decrease the effectiveness of tamoxifen in preventing breast cancer.

Researchers examined women taking tamoxifen along with Paxil, Prozac, or Zoloft and found that such women were nearly twice as likely to suffer a return of breast cancer compared to women who took tamoxifen without an SSRI.

Millions of Americans take SSRIs for treatment of depression, anxiety disorders, and personality disorders. The drugs also are prescribed to some women to treat hot flashes that may be caused by taking tamoxifen.

Tamoxifen works along with a liver enzyme to change into the tumor-fighting compound, called endoxifen. However, many SSRI antidepressants block the same enzyme, which can keep tamoxifen from working, researchers said.

The study is the first time researchers have found evidence of SSRIs limiting the effectiveness of tamoxifen in fighting cancer, officials said.

While Paxil, Prozac, and Zoloft are stronger forms of SSRIs which block the liver enzyme, other drugs, considered weaker SSRIs, were not associated with interfering with the work of cancer drugs, researchers said. Those weaker drugs include drugs such as Celexa, Lexapro, and Luvox, researchers said.

For the study, researchers examined the records of about 10 million patients and identified about 1,300 women who were taking tamoxifen to treat breast cancer between 2003 and 2005. Of those women, 353 women also were taking Paxil, Prozac, or Zoloft, while another 137 were taking a weaker version of SSRIs.

The women were followed for two years, during which time 16 percent of women taking both tamoxifen and SSRIs suffered a recurrence of cancer compared to just 7.5 percent of women in the tamoxifen-only study group. Women taking weaker SSRIs saw recurrence rates similar to those taking tamoxifen only, the study found.

Researchers said more study is needed to further explore the relationship between taking tamoxifen and SSRIs and how the drug combination can interfere with cancer-fighting.

No related posts.