Flutamide Side Effects

Medically reviewed by Drugs.com. Last updated on Jun 21, 2024.

Applies to flutamide: oral capsule.

Important warnings This medicine can cause some serious health issues

Oral route (capsule)

Liver failure has been reported in patients taking flutamide.

Evidence of hepatic injury occurred usually within the first 3 months and included elevated serum transaminase levels, jaundice, hepatic encephalopathy, and death related to acute hepatic failure.

Serum transaminase levels should be measured prior to starting treatment, monthly for the first 4 months of therapy, and periodically thereafter.

Flutamide is not recommended in patients whose ALT values exceed twice the upper limit of normal and should be discontinued if the ALT rises above 2 times the upper limit of normal or jaundice occurs during therapy.

Serious side effects of flutamide

Along with its needed effects, flutamide may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking flutamide:

More common side effects

• black, tarry stools
• bloody or cloudy urine
• continuing diarrhea
• continuing stomach pain
• difficult, burning, or painful urination
• frequent urge to urinate
• pale skin
• troubled breathing with exertion
• unusual bleeding or bruising
• unusual tiredness or weakness

Less common side effects

• blurred vision
• chest pain
• chills
• cough
• difficulty with breathing
• dizziness
• drowsiness
• fever
• headache
• nervousness
• pounding in the ears
• shortness of breath
• slow or fast heartbeat
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• swelling
• swollen glands

Rare side effects

• abdominal or stomach pain
• clay-colored stools
• dark urine
• general tiredness and weakness
• itching
• light-colored stools
• loss of appetite
• nausea and vomiting
• rash
• tumor
• unpleasant breath odor
• upper right abdominal pain
• vomiting of blood
• yellow eyes and skin

Incidence not known

• back, leg, or stomach pains
• bleeding gums
• blistering, peeling, or loosening of the skin
• bluish-colored lips, fingernails, or palms
• discoloration of the urine
• dizziness or lightheadedness
• flushing or redness of the skin
• general body swelling
• headache
• itching
• joint or muscle pain
• nosebleeds
• rapid heart rate
• red irritated eyes
• red skin lesions, often with a purple center
• unusually warm skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking flutamide:

Symptoms of overdose

• goosebumps
• shakiness and unsteady walk
• tearing of the eyes
• unsteadiness, trembling, or other problems with muscle control or coordination
• weight loss

Other side effects of flutamide

Some side effects of flutamide may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common side effects

• decreased interest in sexual intercourse
• diarrhea
• feeling of warmth
• inability to have or keep an erection
• indigestion
• loss in sexual ability, desire, drive, or performance
• passing of gas
• redness of the face, neck, arms and occasionally, upper chest
• stomach pain, fullness, or discomfort
• sudden sweating
• swelling of the breasts or breast soreness in both females and males

Less common side effects

• depression
• drowsiness
• fear or nervousness
• mood or mental changes

For healthcare professionals

Applies to flutamide: oral capsule.

Hepatic adverse events

• Rare (0.01% to 0.1%): Abnormal liver function tests, hepatic dysfunction, jaundice
• Very rare (less than 0.01%): Cholestatic jaundice, hepatic encephalopathy, liver cell necrosis, fatal hepatotoxicity^[Ref]

Hematologic

• Rare (0.01% to 0.1%): Anemia, leucopenia, thrombocytopenia
• Very rare (less than 0.01%): Hemolytic anemia, megalocytic anemia, methemoglobinemia, sulfhemoglobinemia, macrocytic anemia^[Ref]

Nervous system

• Rare (less than 0.1%): Dizziness, headache, numbness, drowsiness
• Frequency not reported: Tiredness, malaise^[Ref]

Cardiovascular

• Very common (10% or more): Hot flushes
• Rare (less than 0.1%): Cardiovascular disorders, hypertension, lymphoedema
• Frequency not reported: QT prolongation, thromboembolism^[Ref]

Dermatologic

• Rare (0.01% to 0.1%): Urticaria, pruritus, ecchymosis, alteration of the hair growth pattern and loss of hair (head), rash
• Very rare (less than 0.01%): Photosensitivity reactions, erythema, ulcers, bullous eruptions, epidermal necrosis^[Ref]

Endocrine

• Very common (10% or more): Gynecomastia (19%)
• Common (1% to 10%): Breast tenderness (7%)^[Ref]

Gastrointestinal

• Very common (10% or more): Nausea, vomiting, diarrhea
• Rare (less than 0.1%): Constipation, ulcer-like pain, dyspepsia, colitis, upset stomach, heartburn, abdominal pain^[Ref]

Musculoskeletal

• Rare (0.01% to 0.1%): Muscle cramps, neuromuscular symptoms, reduced bone mineral density, osteoporotic disorders, arthralgia, myalgia^[Ref]

Psychiatric

• Rare (0.01% to 0.1%): Anxiety, depression, confusion, nervousness^[Ref]

Genitourinary

• Frequency not reported: Loss of libido^[Ref]

Respiratory

• Rare (0.01% to 0.1%): Interstitial pneumonitis, dyspnea
• Very rare (less than 0.01%): Cough, interstitial lung disease^[Ref]

Immunologic

• Rare (0.01% to 0.1%): Lupus-like syndrome
• Very rare (less than 0.01%): Herpes zoster^[Ref]

Ocular

• Rare (less than 0.1%): Blurred vision^[Ref]

Metabolic

• Common (1% to 10%): Increased appetite
• Rare (less than 0.1%): Anorexia^[Ref]

Oncologic

• Very rare (less than 0.01%): Neoplasm of the male breast^[Ref]

Frequently asked questions

• How does flutamide work in prostate cancer?

Further information

Flutamide side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer