03/24/2010 - Articles

Paroxetine and tamoxifen not a good combo

By: Susan Aldridge, medical journalist, PhD


Paroxetine is an antidepressant in the selective serotonin reuptake inhibitors (SSRI) group. Antidepressants, including paroxetine, are often used in women with breast cancer who may also be taking the drug tamoxifen. A study from researchers in Toronto, Canada now suggests that women with breast cancer who take paroxetine and tamoxifen are at increased risk of death. The reason is that paroxetine interferes with the action of tamoxifen, which must be converted in the liver to an active compound called endoxifen. . Some drugs do interfere with this conversion process including, according to this new study, paroxetine.

The researchers studied the health care records of nearly 2,500 women aged 66 or older who had breast cancer and had received tamoxifen between 1993 and 2005. Around 30% of the women received an antidepressant at some stage during their tamoxifen treatment and paroxetine was the one most commonly prescribed. The use of paroxetine, but not other SSRIs, was linked to an increased long-term risk of death from breast cancer in a way that was directly linked to the degree of overlap of use of the two drugs. The researchers conclude that treatment with paroxetine for 41% of the time on tamoxifen results in one additional breast cancer death at five years for every 20 women thus treated. Therefore, the choice of antidepressant to teat women on tamoxifen who also have breast cancer can significantly influence survival prospects. This is an important drug-drug interaction and needs to be taken fully into account when planning treatment for a woman with breast cancer. In short, doctors should not prescribe paroxetine and tamoxifen together. There are other SSRIs, and other classes of antidepressant, which can be used instead for treatment of depression co-existing with breast cancer.



Kelly C et al Selective serotonin reuptake inhibitors and breast cancer mortality in women receiving tamoxifen: a population based cohort study British Medical Journal Online First 9th February 2010doi:10.1136/bmj


Created on: 03/24/2010
Reviewed on: 03/24/2010

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