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Indications and Dosage
Oral
Advanced prostate cancer Adult: In combination with LH-releasing hormone (LHRH) agonist as initial or adjunctive therapy in patients already receiving LHRH-agonist, surgically castrated or unresponsive to other forms of hormonal manipulation: 250 mg tid, started at least 3 days before LHRH agonist and continued thereafter at the same dose.
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Hepatic Impairment
Severe: Contraindicated.
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Administration
May be taken with or without food.
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Contraindications
Severe hepatic impairment or serum transaminases >2-3 times the ULN.
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Special Precautions
Patient with CV disease, history or risk factors for QT prolongation; diabetes; G6PD deficiency, haemoglobin M disease. Smokers. Not indicated for use in women. Hepatic and renal impairment.
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Adverse Reactions
Significant: Aniline toxicity (e.g. haemolytic anaemia, methaemoglobinaemia, cholestatic jaundice), gynaecomastia, interstitial pneumonia; decreased glucose tolerance, prolonged QT interval, increased plasma testosterone, increased estradiol levels, fluid retention; reduced BMD.
Blood and lymphatic system disorders: Anaemia, leucopenia, thrombocytopenia. Cardiac disorders: Dyspnoea. Gastrointestinal disorders: Diarrhoea, nausea, vomiting, rectal haemorrhage, proctitis. General disorders and administration site conditions: Tiredness. Hepatobiliary disorders: Abnormal liver function (transient). Metabolism and nutrition disorders: Increased appetite, anorexia, oedema. Neoplasms benign, malignant and unspecified: Tumour flares. Nervous system disorders: Dizziness. Psychiatric disorders: Insomnia, somnolence. Renal and urinary disorders: Cystitis, haematuria; amber or yellow-green urine discolouration. Reproductive system and breast disorders: Galactorrhoea, breast tenderness, decreased libido, impotence. Skin and subcutaneous tissue disorders: Rash. Vascular disorders: Hot flushes, hypertension. Potentially Fatal: Hepatotoxicity. |
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Patient Counseling Information
This drug may cause dizziness or drowsiness; if affected, do not drive or operate machinery.
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Monitoring Parameters
Monitor serum transaminase levels prior to treatment initiation, then monthly for 4 months, and periodically thereafter; CBC and prostate-specific antigen (PSA) at baseline and during treatment; LFTs at the 1st sign or symptoms suggestive of liver dysfunction (e.g. anorexia, dark-coloured urine, right upper quadrant tenderness, jaundice, flu-like symptoms); BMD at baseline, then after 1 year of treatment, and as clinically indicated. Monitor methaemoglobin levels in at-risk patients; respiratory symptoms during the 1st few weeks of therapy. May determine sperm counts regularly during prolonged therapy in patients who have not received surgical or medical castration.
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Overdosage
Symptoms: Breast tenderness, gynaecomastia, and increased AST. Management: Supportive treatment. May induce vomiting if necessary. May consider performing gastric lavage. Closely observe patient and frequently monitor vital signs.
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Drug Interactions
Increased risk of QT interval prolongation and torsades de pointes with class IA (e.g. disopyramide, quinidine) or class III (e.g. sotalol, dofetilide, amiodarone) antiarrhythmics, antipsychotics (e.g. chlorpromazine), macrolide antibiotics (e.g. clarithromycin, erythromycin), moxifloxacin, methadone, salbutamol. Increased prothrombin time with oral anticoagulants (e.g. warfarin). May increase plasma concentrations of theophylline.
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Food Interaction
Increased risk of liver toxicity with alcohol.
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Action
Description:
Mechanism of Action: Flutamide, a nonsteroidal antiandrogen agent, inhibits androgen uptake and blocks the binding of androgen in target tissues. Pharmacokinetics: Absorption: Rapidly and completely absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 1-2 hours. Distribution: Plasma protein binding: 94-96% (flutamide); 92-94% (2-hydroxyflutamide). Metabolism: Rapidly and extensively metabolised in the liver primarily into 2-hydroxyflutamide (major active metabolite) and other metabolites. Excretion: Mainly via urine (as unchanged drug and metabolites); faeces (approx 4%). Elimination half-life: Approx 6 hours (2-hydroxyflutamide). |
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Chemical Structure
 Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 3397, Flutamide. https://pubchem.ncbi.nlm.nih.gov/compound/Flutamide. Accessed Oct. 27, 2020. |
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Storage
Store between 20-25°C. Protect from light. Follow applicable procedures for receiving, handling, administration, and disposal.
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MIMS Class
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ATC Classification
L02BB01 - flutamide ; Belongs to the class of anti-androgens. Used in treatment of neoplastic diseases.
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References
Anon. Flutamide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 08/10/2020. Buckingham R (ed). Flutamide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/10/2020. Fluta-cell 250 mg Tablet (Hongkong Medical Supplies Ltd). MIMS Hong Kong. http://www.mims.com/hongkong. Accessed 08/10/2020. Flutamide 250 mg Tablets (Waymade Plc). MHRA. https://products.mhra.gov.uk/. Accessed 08/10/2020. Flutamide Capsule (Cipla USA Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 08/10/2020. Joint Formulary Committee. Flutamide. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 08/10/2020. Mylan New Zealand Ltd. Flutamin 250 mg Tablet data sheet 24 June 2020. Medsafe. http://www.medsafe.govt.nz/. Accessed 08/10/2020.
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