Tamoxifen Side Effects and Considerations

Serious Side Effects

The American Society of Clinical Oncology notes that tamoxifen doubles the baseline risk of endometrial cancer, with a relative risk of 2.4-fold (95% CI 1.5-4.0) compared to placebo, primarily in women ≥50 years old 1
The American Society of Clinical Oncology recommends that patients on tamoxifen should have a baseline gynecologic examination and annual follow-up thereafter, with prompt evaluation of abnormal bleeding 1
Tamoxifen increases the risk of venous thromboembolism 1.7-fold (95% CI 1.27-2.36), with 14 additional events per 1,000 women over median follow-up 2
The American Heart Association notes that tamoxifen increases ischemic stroke risk 1.82-fold (95% CI 1.41-2.36), particularly in women ≥50 years 3
Tamoxifen is contraindicated in women with prior stroke or transient ischemic attack, as stated by the American Heart Association 3

The National Comprehensive Cancer Network reports that night sweats are a common side effect of tamoxifen 4
Vaginal discharge occurs in 35-55% of patients on tamoxifen, with a 3.44-fold increase in risk, according to the American College of Obstetricians and Gynecologists 3
The American Academy of Ophthalmology notes that cataract risk increases 1.14-fold (95% CI 1.01-1.29) with tamoxifen use, with 14 additional cases per 1,000 women 3

The National Osteoporosis Foundation states that tamoxifen has protective effects on bone in postmenopausal women, preserving bone mineral density and potentially reducing fracture risk 7
The American College of Cardiology notes that tamoxifen may reduce fatal myocardial infarction through favorable effects on serum lipids and cholesterol, and lower rates of hypercholesterolemia and hypertension compared to aromatase inhibitors 7

The American Society of Clinical Oncology recommends avoiding concurrent use of CYP2D6 inhibitors (paroxetine, fluoxetine, bupropion) with tamoxifen, as they reduce conversion to active endoxifen metabolite, potentially decreasing efficacy 7
If CYP2D6 inhibitors are necessary for other conditions, the American Society of Clinical Oncology suggests considering alternative endocrine therapy 7

The American Cancer Society notes that most patients maintain well-preserved quality of life on tamoxifen, with severity of common side effects being mild-to-moderate for the majority 7
The National Comprehensive Cancer Network recommends considering switching treatment if adverse effects are intolerable or if patients are persistently noncompliant 7