Women taking a popular anti-depressant alongside tamoxifen for breast cancer are more likely to die from the disease, according to new research.
A US study found that paroxetine (brand name Seroxat) could interfere with the breast cancer drug and put patients at a greater risk of dying from the disease, compared with those on other anti-depressants.
The findings have "major implications for clinical practice", researchers from the Sunnybrook Health Sciences Centre and the University of Toronto in Canada wrote in the British Medical Journal (BMJ).
Up to one in four women with breast cancer can experience some degree of depression and antidepressants are also prescribed for hot flushes, they said.
All 2,430 women were taking tamoxifen and one of five anti-depressants known as selective serotonin reuptake inhibitors (SSRIs), including paroxetine, which was the most commonly prescribed drug.
Over a typical follow-up of 2.4 years, 374 women died from breast cancer.
Analysis of health records showed women taking paroxetine were far more likely to die from breast cancer and were slightly more likely to die from any other cause when compared with women not on paroxetine.
The researchers concluded: "We estimate that use of paroxetine for 41% of tamoxifen treatment (the median overlap in our sample) would result in one additional breast cancer death within five years of cessation of tamoxifen for every 19.7 patients so treated; the risk with more extensive overlap would be greater."