The incidence of side effects is described in accordance with the following gradation: most often (10% and higher), less often (from 1 to 10%), rarely (less than 1%).
When using the drug in monotherapy
Most often: gynecomastia and / or pain in the region of the breast, sometimes accompanied by galactorrhea. These phenomena disappear after withdrawal of treatment or dose reduction.
Less often: diarrhea, nausea, vomiting, increased appetite, insomnia,
increased fatigue, transient liver dysfunction, hepatitis.
Rarely: hepatitis or jaundice (including cholestatic), liver necrosis, hepatic encephalopathy, increased activity of transaminases (these side effects are usually reversible after discontinuation of therapy,however, there were reports of fatal outcomes due to severe hepatic insufficiency with flutamide therapy); subcutaneous hemorrhages, shingles, skin itching, lupus-like syndrome; anorexia, heartburn, constipation, indigestion; decreased libido, headache, hot flashes (fever, increased sweating), increased blood pressure, dizziness, weakness, visual acuity, thirst, chest pain, swelling (fingers, feet, shins), anxiety,
depression and thrombocytopenia. With prolonged treatment, suppression of spermatogenesis was noted. Some cases of hemolytic anemia, macrocytic anemia, methemoglobinemia, reaction of increased photosensitivity (including erythema, ulceration of the skin, bullous rash, epidermal necrolysis) have been noted. Sometimes in patients there is a change in the color of urine from amber to yellow-green.
When treated in combination with GnRH agonists
Most often: "hot flashes" (fever, increased sweating), decreased libido, impotence, diarrhea, nausea, vomiting. The incidence of these side effects, with the exception of diarrhea (more pronounced when used in conjunction with flutamide), is the same as with monotherapy with GnRH agonists.
Less often: gynecomastia, anemia, leukopenia, thrombocytopenia, lack of appetite, swelling, symptoms of neuromuscular disorders, difficulty urinating, increased blood pressure and side effects from the central nervous system (drowsiness, depression, confusion, anxiety, neurosis).
Rarely: respiratory failure, hepatic insufficiency, hepatitis, cholestatic jaundice, necrosis of the liver, hepatic encephalopathy, increased photosensitivity, methemoglobinemia.