Who should avoid taking tamoxifen?

Blood clots. Pts with a history of blood clots and/or a history of abnormal pap smears should not take tamoxifen. If there is a family history of clotting disorders or uterine cancer, tamoxifen should not be used.
Pregnant women. Tamoxifen is most often prescribed for the prevention or treatment of hormone-sensitive breast cancer. Tamoxifen may increase the risk of blood clots, strokes, uterine cancer, and cataracts, however the benefits usually outweigh the risk. Pregnancy should be avoided when on tamoxifen due to it's association with birth defects in animal studies.