Dr Lee had much to say about Tamoxifen and breast cancer, but the reality is that there are many women who do take it and I came across a piece of information that I suggest you pass on to any woman you know in this situation.
Cancer, wherever it occurs, brings a whole maelstrom of emotions and feelings along with the physical effects and depression is certainly one of them. If a woman with breast cancer takes Paroxetine, the generic name of an SSRI drug now commonly prescribed for depression, there is a serious risk to consider.
Paroxetine may be given under the trade names of Seroxat or Paxil and if taken at the same time as Tamoxifen has an increased risk of death according to a study published on the British Medical Journal website. Why the increased risk? Because paroxetine itself does not cause or influences the course of breast cancer but it impairs the effectiveness of Tamoxifen.
Whatever the advisability or not of taking Tamoxifen, the reality is that in order to work, it must be converted into an active metabolite (endoxifen) by the liver and antidepressants can interfere with this process. Because it is common for women with breast cancer to be on antidepressants for long periods of time, and although many antidepressants have little or no impact on tamoxifen’s metabolism, paroxetine is a potent inhibitor of the metabolic step that converts tamoxifen to endoxifen.
This latest research was carried out by Dr Catherine Kelly and colleagues at the Institute for Clinical Evaluative Sciences (ICES) in Toronto and they concluded that Paroxetine, but not other SSRIs, in combination with Tamoxifen, was associated with an increased long-term risk of breast cancer death. The researchers estimate that treatment with paroxetine for 41 percent of the total time on Tamoxifen will result in one additional breast cancer death at five years for every 20 women so treated. One of the study’s authors, David Juurlink a scientist at ICES, went further and stated that “these results highlight a drug interaction that is extremely common, widely underappreciated and potentially life-threatening, yet uniformly avoidable.”
This means that the choice of antidepressant can significantly influence survival in women taking Tamoxifen for breast cancer, so needs to be thoroughly discussed with your doctor or cancer team. Any women currently taking this potentially lethal duo also needs to discuss withdrawal of the antidepressant as it should not be abruptly withdrawn to minimise side effects.