With monotherapy. The most common adverse events are gynaecomastia and / or pain in the thoracic glands, sometimes accompanied by galactorrhea. These phenomena disappear upon discontinuation or after a dose reduction. Less frequent diarrhea, nausea, vomiting, increased appetite, insomnia, fatigue, transient liver dysfunction, hepatitis.
In rare cases, the following side effects are noted: decreased libido, gastrointestinal disturbances (lack of appetite, heartburn, constipation, pain similar to stomach ulcer pain), peripheral edema,subcutaneous hemorrhage, shingles, itching, lupus-like syndrome, headache, dizziness, weakness, visual acuity, thirst, chest pain, anxiety, depression, lymphangiectatic edema, change in urine color (from amber to yellow-green). With prolonged treatment, suppression of spermatogenesis was noted.
The following spontaneous side effects were also noted: hemolytic anemia, macrocytic anemia, methemoglobinemia, sulfemoglobinemia, increased photosensitivity reactions (including erythema, ulceration, bullous rash, epidermal necrolysis), obstructive jaundice, hepatic encephalopathy, liver necrosis, increased urea nitrogen and creatinine levels. These side effects usually occur after discontinuation of therapy. However, there are reports of a fatal outcome due to severe liver damage caused by the administration of flutamide. Very rarely there is hyperglycemia and exacerbation of diabetes mellitus.
When treated in combination with GnRH agonists. Most often, "hot flashes" (fever, sweating), decreased libido, impotence, diarrhea, nausea, vomiting are possible.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. The incidence of gynecomastia with combination therapy is significantly lower than in monotherapy, and is comparable to the incidence of placebo.
Rarely, the following side effects may occur: anemia, leukopenia, thrombocytopenia, gastrointestinal disorders of unclear etiology, lack of appetite, peripheral edema, symptoms of neuromuscular disorders, jaundice, symptoms of genitourinary system disorders, increased blood pressure and side effects from the central nervous system (drowsiness, depression, confusion, anxiety, neurosis). In very rare cases, interstitial lung diseases, hepatitis, and increased photosensitivity may occur.