Three antidepressants have been found to reduce the effectiveness of the breast-cancer suppressant tamoxifen, according to research by Medco Health Solutions.
The study has found that taking Prozac, Paxil/Seroxat and to a lesser extent Zoloft/Lustral can substantially reduce the benefits provided by tamoxifen, prescribed for women with hormone-receptor-positive, early-stage breast cancer.
Researchers evaluated 353 women taking tamoxifen plus other drugs and 945 women taking tamoxifen alone for a year, and followed up after two years.
Breast cancer recurred in 7% of women on tamoxifen alone, and in 14% of women also taking mainly the three antidepressants. This result was not observed in women taking the antidepressants Cipramil, Lexapro or Luvox (fluvoxamine).
Tamoxifen works by binding to oestrogen receptors on tumours, producing a nuclear complex that decreases DNA synthesis and inhibits oestrogen effects.
The drug causes cells to remain in the G0 and G1 phases of the cell cycle. Because it prevents precancerous cells from dividing but does not cause cell death, tamoxifen is cytostatic rather than cytocidal.
Copyright Press Association 2009