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 thoracic glands, sometimes accompanied by galactorrhea. These phenomena disappear after withdrawal of treatment or dose reduction.
Less often: diarrhea, nausea, vomiting, increased appetite, insomnia, fatigue, transient liver dysfunction, hepatitis.
Rarely: hepatitis or jaundice (including cholestatic), liver necrosis, hepatic encephalopathy, increased transaminase activity (these side effects are usually reversible after discontinuation of therapy, but there have been 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, sweating), decreased libido, impotence, diarrhea, nausea, vomiting. The incidence of these side effects, with the exception of diarrhea (more pronounced when used in combination with flutamide), is the same as for 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 failure, hepatitis, cholestatic jaundice, liver necrosis, hepatic encephalopathy, increased photosensitivity, methemoglobinemia.