Megestrol
progestins
Progestogens (progestins)Pregnancy: contraindicated
Contraindicated: it may harm the fetus. Breastfeeding is stopped during treatment.
A synthetic progestogen taken by mouth. It treats some breast and endometrial cancers and stimulates appetite in AIDS-related weight loss.
Also called: Megestrol acetate
Quick facts
- Group
- Progestogens (progestins)
- Target
- Progesterone receptor (PGR); it also has glucocorticoid activity
- Used for
- Palliative treatment · Palliative treatment · Anorexia
- Key effects
- Weight gain and fluid retention · Diarrhoea · Rash
- Monitor
- Blood glucose · Weight and oedema
- ATC
- L02AB01
No doses: the clinician sets them by the current guideline.
Mechanism of action
Megestrol acetate is a synthetic derivative of progesterone. Through the progesterone receptor it opposes oestrogen-driven growth of hormone-sensitive breast and endometrial tumours. It increases appetite and weight by a mechanism that is not fully known. It also binds the glucocorticoid receptor, which explains Cushing-like effects, raised blood glucose and suppression of the adrenal axis with long use.
- Megestrol activates progesterone receptors
- Oestrogen-driven tumour growth is opposed
- Appetite and weight increase (mechanism not fully known)
- Glucocorticoid-like action suppresses the adrenal axis
Indications
- Palliative treatment of advanced breast cancer (tablets) Breast cancer →
- Palliative treatment of advanced endometrial cancer (tablets) Endometrial cancer →
- Anorexia, cachexia or unexplained significant weight loss in people with AIDS (oral suspension) HIV infection and AIDS →
Adverse effects
Common
- Weight gain and fluid retention
- Diarrhoea, flatulence and nausea
- Impotence and reduced libido
- Rash
- Breakthrough vaginal bleeding
- High blood pressure
Contraindications
- Known or suspected pregnancy
- Hypersensitivity to megestrol acetate
- Caution: history of thromboembolic disease
Key interactions
- Warfarin
- INR may rise; closer monitoring
- Insulin and other diabetes treatment
- Requirements may increase because of glucocorticoid-like effects
What is monitored
- Blood glucose
- Weight and oedema
- Signs of venous thromboembolism
- Signs of adrenal insufficiency during stress, illness or after stopping
- INR in people taking warfarin
Administration and safety
- The oral suspension is shaken well before each use
- Look-alike risk: the regular and concentrated oral suspensions are not interchangeable
- Not stopped abruptly after long use without the prescriber, because of adrenal suppression
- Surgeons and dentists are told before procedures
Pregnancy and breastfeeding
Contraindicated: it may harm the fetus. Breastfeeding is stopped during treatment.
Nursing care
- Ask about leg pain or swelling, chest pain or breathlessness
- Check glucose, especially in people with diabetes
- During severe illness or surgery, consider stress-dose glucocorticoid needs
- Advise reliable contraception; irregular periods do not mean pregnancy cannot occur
- In older adults it is usually not used for appetite loss
Pharmacokinetics
- Absorption
- Taken by mouth as tablets or oral suspension
- Elimination
- Mainly by the kidney
Test yourself
Think of the answer, then tap the question to see it.
Why can long-term megestrol cause adrenal insufficiency?
Its glucocorticoid activity suppresses the pituitary-adrenal axis; crisis can occur during stress or after stopping.
Which serious vascular adverse effect is linked to megestrol?
Venous thromboembolism, such as thrombophlebitis and pulmonary embolism.
What is the AIDS-related indication of megestrol oral suspension?
Anorexia, cachexia or unexplained significant weight loss in people with AIDS; it is not used to prevent weight loss.
Connections
← Back to the class: Progestogens (progestins)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - MEGESTROL ACETATE suspension (DailyMed (U.S. National Library of Medicine), 2026); Megestrol: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.