Generally speaking impotence does not seem to be a problem for men who are taking tamoxifen as part of their treatment for breast cancer. But it may occur very occasionally.

Usually if a man takes tamoxifen the levels of the male hormone, testosterone increase. But rarely, the drug has the opposite effect, reducing testosterone levels and causing impotence. Nobody is quite sure why this happens.

If a man develops impotence due to tamoxifen stopping the drug should solve the problem. Other drugs, called aromatase inhibitors, may be used as an alternative to tamoxifen. If impotence develops as a result of tamoxifen substituting an aromatase inhibitor may help.

Reference

• Collinson MP et al. Breast, 1993; 2: 48-49. Two case reports of tamoxifen as a cause of impotence in male subjects with breast cancer.