This result is similar to results from other research and suggests that Paxil interferes with tamoxifen's ability to treat breast cancer. An enzyme called CYP2D6 helps tamoxifen work in the body. Some research has shown that women with an abnormal gene that blocks their bodies' ability to produce CYP2D6 don't get the same benefits from tamoxifen as women who produce CYP2D6.
Earlier research has shown that some medicines interfere with how CYP2D6 works, which reduces tamoxifen's effectiveness against breast cancer. These medicines include some antidepressants known as serotonin-specific reuptake inhibitors SSRIs -- including Paxil -- and serotonin-norepinephrine reuptake inhibitors SNRIs. These antidepressant medicines are sometimes used to ease symptoms of depression or to manage hot flashes that can be a side effect of hormonal therapy in women being treated for breast cancer.
Some other widely used medicines:. In this very large study, researchers looked at the medical records of more than 24, postmenopausal women diagnosed with hormone-receptor-positive breast cancer from to All the women were treated with tamoxifen and 7, of the women also took one or more of the following antidepressant medicines for some period of time while taking tamoxifen:. The researchers followed the women for about 2. The researchers narrowed the study to compare the 2, women who took only one antidepressant while on tamoxifen to women who didn't take an antidepressant.
Most of the women who took only one antidepressant took Paxil The increased risk of dying from breast cancer was different depending on how long a woman took Paxil and tamoxifen at the same time called "therapeutic overlap".
Perhaps the most important limitation of this study is that the mean follow-up time was 2. As the authors indicate, this limits the conclusiveness of their analysis as it may not pertain to the long-term safety profile of concomitant use of tamoxifen and the named SSRIs.
This point should be further considered when taking into account that the authors were limited in their ability to distinguish stages of breast cancer due to using claims data. In an editorial in the same issue of BMJ , Juurlink outlines the importance of this issue and the controversial nature of such studies.
Such studies are important, he indicates, as tamoxifen has been monumental in reducing the recurrence and mortality of breast cancer. He points out that the possible consequences of said interaction are not acute, and are delayed by years. Tamoxifen pharmacokinetics, he notes, involves processes other than CYP2D6 which adds to the complexity of such studies.
Consequently this study does little to disprove a meaningful interaction between tamoxifen and CYP2D6 inhibitors. This study does illustrate, however, just how challenging it can be to conduct such studies. In short, drawing any conclusions related to interaction between tamoxifen and antidepressants would be premature at this stage. This is especially true considering the life saving effects of tamoxifen and the fact that we can likely sidestep any possible harm due to possible medication interactions.
The editorial points out the following three logical steps to guide co-prescription of these medications 2 :. Of note, while the above recommendations are quite reasonable, there are many situations in which a women has responded to a potent CYP2D6 medication well and alternatives have not proven effective.
A discussion of risks, benefits and alternatives in such situations is essential so that patients may navigate the course of treatment in the most informed fashion.
Previous Next. View Larger Image. Treatment of Depression in Women with Breast Cancer Roughly half of women diagnosed with breast cancer report symptoms of depression, anxiety or both during the first year of receiving the diagnosis 1.
Venlafaxine has little or no effect on the metabolism of tamoxifen and may be considered the safest choice of antidepressants.
Desvenlafaxine is not metabolized by the P system and may consequently be another option. Mirtazapine has not been extensively studied, but existing research suggests minimal effect on CYP2D6. The remaining commonly prescribed antidepressants have mild to moderate degrees of CYP2D6 inhibition. Conclusions: Clinicians treating patients with breast cancer should review the prescription profiles of their patients to evaluate the need for treatment modification.
There are safe options for the treatment of depression and clinicians and patients should bear in mind the health risks of untreated depressive states.
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