Conflicting evidence on Tamoxifen and anti-depressants

Women who take anti-depressants, while on tamoxifen, may or may not be at risk of recurrence. According to ABC News, conflicting evidence has emerged at the annual meeting of the American Society for Clinical Oncology. Scientists in the United States and the Netherlands reached opposite conclusions 

Some researchers think that some of the most popularly presecribed antidepressants, SSRIs, which include Prozac (fluoxetine) and Paxil (paroxetine),  may prevent tamoxifen from working as well as it should.  However, another group of researchers found no conclusive evidence in their reserach.

One particular group of these antidepressants works by inhibiting an enzyme known as CYP2D6, which coincidentally helps the body process tamoxifen. Researchers want to know if the potential for conflict between the two agents yields real problems for breast cancer survivors. 

In the U.S. study, an analysis of medical records of almost 1,000 breast cancer patients showed that use of CYP2D6 inhibitors almost doubled the risk of breast cancer recurrence within two years after patients started tamoxifen.

In contrast, Dutch investigators reported just the opposite when they looked at the records of 1,962 breast cancer patients who took tamoxifen between 1994 and 2006. They found no evidence that CYP2D6 inhibitors increased the risk of breast cancer recurrence in women taking tamoxifen.

This of course is far from reassuring to those women who take anti-depressants either to combat the hot flushes associated with hormone therapy, or who are dealing with depression following their treatment.

“We still have a lot of work to do,” said Dr. Lori Pierce, a breast cancer specialist at the University of Michigan, who was not involved in either study. ” Some SSRIs do not inhibit the enzyme. Using a different drug known as an aromatase inhibitor instead of tamoxifen to prevent breast cancer recurrence is another possible option.

“You should make the best judgment in terms of the appropriate medication for the patient, given her disease,” added Pierce. “There are ways to work around the problem if tamoxifen is the best drug for a patient. But certainly aromatase inhibitors are very important drugs in our armamentarium for postmenopausal women with breast cancer.”

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