In the treatment of tamoxifen, the most frequent adverse reactions associated with its antiestrogenic effect, manifested in the form of paroxysmal sensations of heat ("hot flashes"), vaginal bleeding or discharge, itching in the genital area, alopecia, pain in the area of the lesion center, ossalgia, weight gain.
Less frequently or rarely, the following adverse reactions were observed: fluid retention, anorexia, nausea, vomiting, constipation, fatigue, depression, confusion, headache, dizziness, drowsiness, fever,skin rash (including individual reports of erythema multiforme, Stevens-Johnson syndrome and bullous pemphigoid), visual impairment, including corneal changes, cataract and retinopathy, retrobulbar neuritis, allergic reactions, including angioedema; decreased libido in men, impotence. Interstitial pneumonitis was rarely observed. At the beginning of treatment, local exacerbation of the disease is possible - an increase in the size of soft tissue formations, sometimes accompanied by a pronounced erythema of affected areas and adjacent areas, which usually occurs within 2 weeks.
The likelihood of thrombophlebitis and thromboembolism may increase.
Often leg cramps are noted.
Transient leukopenia and thrombocytopenia, as well as an increase in the activity of "hepatic" enzymes, which are very rarely accompanied by more severe impairment of liver function, can rarely be observed; such as fatty liver infiltration, cholestasis and hepatitis.
An increase in serum triglyceride concentrations in some cases combined with pancreatitis was rarely observed.
In some patients with bone metastases, hypercalcaemia was observed at the beginning of treatment.
Tamoxifen causes amenorrhea or irregularity of menstrual periods in premenopausal women, as well as the reversible occurrence of cystic ovarian tumors.
With long-term treatment with tamoxifen, there may be changes in the endometrium, including hyperplasia, polyps, development of uterine fibroids and in single cases - endometrial cancer, uterine sarcoma.