Oral Palliative treatment of endometrial carcinoma
Adult: As tab: 40-320 mg daily in divided doses for at least 2 months. Elderly: Initiate at the lower end of the dosing range.
Oral Palliative treatment of breast carcinoma
Adult: As tab: 160 mg once daily as a single dose or in divided doses for at least 2 months. Elderly: Initiate at the lower end of the dosing range.
Oral AIDS-related weight loss, Anorexia in patients with AIDS, Anorexia in patients with cancer, Cachexia in patients with AIDS, Cachexia in patients with cancer
Adult: As tab or susp containing 40 mg/mL: 400-800 mg daily. As susp containing 125 mg/mL: 625 mg once daily. Megestrol suspensions are not equivalent on a mg-per-mg basis and are not interchangeable. Elderly: Initiate at the lower end of the dosing range.
Administration
standard formulation: Should be taken with food. Megace ES: May be taken with or without food.
Contraindications
Pregnancy and lactation.
Special Precautions
Patient with history of thromboembolic disease, diabetes mellitus. Not indicated for prevention of weight loss. Renal and hepatic impairment. Elderly.
Adverse Reactions
Significant: Weight gain, thrombophlebitis, hypothalamic-pituitary-adrenal (HPA) axis suppression, Cushingoid syndrome, new-onset or exacerbation of diabetes mellitus (long-term use); vaginal bleeding or discharge. Cardiac disorders: Cardiac failure, dyspnoea. Endocrine disorders: Hypercalcaemia. Gastrointestinal disorders: Constipation, diarrhoea, flatulence, nausea, vomiting. General disorders and administration site conditions: Asthenia, pain, oedema, malaise. Metabolism and nutrition disorders: Hyperglycaemia, increased appetite. Neoplasms benign, malignant and unspecified: Tumour flare. Nervous system disorders: Carpal tunnel syndrome. Psychiatric disorders: Altered mood, lethargy. Renal and urinary disorders: Pollakiuria. Reproductive system and breast disorders: Menorrhagia, erectile dysfunction. Skin and subcutaneous tissue disorders: Alopecia, rash. Vascular disorders: Hypertension, hot flush. Potentially Fatal: Pulmonary embolism.
May decrease exposure of indinavir. May reduce the therapeutic effect of anticoagulants, antidiabetic agents.
Action
Description: Megestrol is a synthetic progestin with anti-estrogenic properties. It disrupts the normal estrogen cycle resulting in a decreased luteinising hormone (LH) titer which may also have direct effect on the endometrium. The mechanism of its antineoplastic effect is unknown but may be due to the pituitary-mediated anti-luteinising effect. Additionally, it antagonises the metabolic effects of catabolic cytokines which may result in appetite stimulation. Onset: Approx 2 months of continuous treatment (breast or endometrial cancer); 2-4 weeks (weight gain). Pharmacokinetics: Absorption: Well absorbed from the gastrointestinal tract. Time to peak plasma concentration: 1-3 hours (tab); 5 hours (susp). Distribution: Enters breast milk. Metabolism: Metabolised in the liver into free steroids and glucuronide conjugates. Excretion: Via urine (57-78%; 5-8% as metabolites); faeces (8-30%). Elimination half-life: 15-20 hours (tab); 20-50 hours (susp).
Chemical Structure
Megestrol Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 19090, Megestrol. https://pubchem.ncbi.nlm.nih.gov/compound/Megestrol. Accessed June 25, 2021.
Storage
Store below 25°C. Protect from heat, light and moisture. This is a cytotoxic drug. Follow applicable procedures for receiving, handling, administration, and disposal.
G03DB02 - megestrol ; Belongs to the class of pregnadien derivative progestogens used in progestogenic hormone preparations. G03AC05 - megestrol ; Belongs to the class of progestogens. Used as systemic contraceptives. L02AB01 - megestrol ; Belongs to the class of progestogens.
References
Anon. Megestrol Acetate. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 16/04/2021.Apotex NZ Ltd. Apo-Megestrol 40 mg & 160 mg tablets data sheet 21 March 2019. Medsafe. http://www.medsafe.govt.nz. Accessed 16/04/2021.Buckingham R (ed). Megestrol Acetate. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 16/04/2021.Joint Formulary Committee. Megestrol Acetate. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 16/04/2021.Megace 160 mg Tablets (Bausch and Lomb UK Ltd.). MHRA. https://products.mhra.gov.uk. Accessed 16/04/2021.Megestrol Acetate Suspension (Proficient Rx LP). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 16/04/2021.Megestrol Acetate Tablet (Bryant Ranch Prepack). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 16/04/2021.Megex-I Suspension 800 mg/20 mL (Imeks Pharma Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 16/04/2021.
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