In the treatment of tamoxifen, the most frequent adverse reactions associated with its anti-estrogenic 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, 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 occasional reports of multiform erythema, syndrome Stevens-Johnson and bullous pemphigoid), visual impairment, including corneal changes, cataracts and retinopathy, retrobulbar neuritis. 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 the affected areas and adjacent areas, which usually occurs within 2 weeks.
The likelihood of thrombophlebitis and thromboembolism may increase.
Often leg cramps are noted.
Sometimes transient leukopenia can occur and thrombocytopenia, as well as an increase in the activity of "liver" enzymes, very rarely accompanied by more severe impairment of liver function, such as fatty liver, cholestasis and hepatitis.
Rarely there was an increase in the level of serum triglycerides in some cases combined with pancreatitis.
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 prolonged treatment with tamoxifen, changes in the endometrium, including hyperplasia, polyps, development of uterine fibroids and in isolated cases - endometrial cancer, uterine sarcoma, can be observed.