A popular antidepressant could interfere with a breast cancer drug and lead to a greater chance of patients dying, researchers said today.
Women taking the antidepressant paroxetine (brand name Seroxat) alongside tamoxifen for breast cancer were more likely to die from the disease than women on other antidepressants, a study found.
The researchers, writing in the British Medical Journal (BMJ), said their results had “major implications for clinical practice”.
Tamoxifen is taken by thousands of British women and works by blocking the female sex hormone oestrogen, which can fuel tumour growth. It is generally given for up to five years following initial treatment or surgery.
The latest research was led by a team from the Sunnybrook Health Sciences Centre and the University of Toronto in Canada.
Up to one in four women with breast cancer can experience some degree of depression.
A total of 2,430 women aged over 66 took part in the research. All were taking tamoxifen and one of five anti-depressants known as selective serotonin reuptake inhibitors (SSRIs), including paroxetine, 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, who believe paroxetine interferes with the metabolism of tamoxifen, found no evidence that other SSRIs increased the risk of death.
They concluded: “Our findings indicate that the choice of antidepressant can significantly affect survival in women receiving tamoxifen for breast cancer.”
They said women should not stop taking tamoxifen and said their study does not imply paroxetine itself causes or influences breast cancer.
“This is simply a situation in which paroxetine impairs the effectiveness of tamoxifen,” they wrote.
Meg McArthur, senior policy and information officer at Breakthrough Breast Cancer, said: “Tamoxifen remains a beneficial treatment for breast cancer and, as several antidepressants are available, doctors should be able to find the right combination for patients. This should not put patients off taking tamoxifen and any concerns should be discussed with their doctor.”