Antidepressants May Hinder Tamoxifen
Some SSRIs May Reduce Effectiveness of Breast Cancer Prevention
Dec. 2, 2003 -- Taking an antidepressant prescribed to combat a
common side effect of the breast cancer prevention drug tamoxifen may actually
decrease its effectiveness in preventing the disease.
A new study shows that the antidepressant Paxil interferes with
the breakdown of tamoxifen into its active anticancer ingredients within the
body. Researchers say findings raise the possibility that the new generation of
antidepressant drugs, known as serotonin reuptake inhibitors (SSRIs) may reduce
the effectiveness of tamoxifen therapy.
Researchers say hot flashes occur in about 80% of women who
take tamoxifen. Doctors often prescribed the drug after breast cancer treatment
to reduce the recurrence of breast cancer or give it to high-risk groups to
prevent breast cancer. SSRIs are often used as an alternative to hormone
replacement therapy to combat hot flashes in women taking tamoxifen.
SSRIs May Interfere With Tamoxifen Treatment
In the study, which appears in the Dec. 3 issue of Journal
of the National Cancer Institute, researchers examined the effect of Paxil
on the metabolism of tamoxifen in blood samples from 12 women with breast
cancer who were being treated with tamoxifen.
They found that Paxil appeared to inhibit the breakdown of
tamoxifen into its active form which acts as a potent antiestrogen to help
fight breast cancer.
In addition, the study showed that four weeks of treatment with
Paxil in conjunction with tamoxifen also reduced the concentrations of another
anticancer component that was present in much higher concentrations before the
women received the antidepressant.
Too Soon to Change Recommendations
Although the findings indicate that SSRIs may interfere with
how the body breaks down tamoxifen, researchers say more research is needed in
larger numbers of women to determine whether these effects have an impact on
the drug's effectiveness in preventing breast cancer.
In an editorial that accompanies the study, Matthew P. Goetz,
MD, and Charles L. Loprinzi, MD, of the Mayo Clinic in Rochester, Minn., agree
that further studies are needed before recommendations against using tamoxifen
and SSRIs together are made.
The editorialists say that the practical implications of this
study will remain unclear until those results are known. They also note that
the effects of each of the newer antidepressants on tamoxifen metabolism may