Background

Some concerns related to tamoxifen use apply only to preventative treatment because they are likely only with long-term use, explains the U.S. National Library of Medication. Other restrictions apply to both prevention and treatment.

Preventative Use

Tamoxifen poses a risk for blood clots and cannot be used preventatively by women who have experienced a blood clot or stroke. Tamoxifen might cause a return of uterine cancer and should not be taken by women with a history of the disease, reports the Mayo Clinic.

All Uses

Doctors rarely prescribe tamoxifen for patients who have a history of cataracts because the drug could cause a recurrence, according to the Mayo Clinic. Women with high cholesterol levels cannot take tamoxifen because the drug might worsen the condition.

Drug Restrictions

Patients who take the blood-thinning drug warfarin should not take tamoxifen because there is a risk of uncontrollable bleeding associated with the combination, according to the U.S. National Library of Medicine.

Other Considerations

Tamoxifen poses a risk for miscarriages or birth defects, and doctors typically do not prescribe the drug for use in pregnant women unless there is no safe alternative.

Source:

Mayo Clinic: Tamoxifen (Oral Route)

U.S. National Library of Medicine DailyMed: Tamoxifen Citrate (Tamoxifen Citrate) Tablet

American Cancer Society: Medicines to Reduce the Risk of Breast Cancer