What is megestrol used for?

Megestrol is a progesterone medication that is used to treat a variety of conditions. Some of the main uses of megestrol include:

Appetite stimulation

One of the most common uses of megestrol is to help stimulate appetite in people with cachexia or anorexia. Cachexia is severe weight loss and muscle wasting that can occur in people with cancer, HIV/AIDS, or other conditions. Megestrol helps increase appetite and prevent further weight loss in people struggling with cachexia.

Cancer treatment

Megestrol may be used as part of cancer treatment in postmenopausal women. It is thought to help slow down or stop the growth of cancers that are stimulated by hormones, such as certain types of breast cancer or endometrial cancer.


Megestrol is sometimes used to help treat endometriosis, which is a condition where tissue similar to the lining of the uterus grows outside of the uterus. Megestrol helps suppress estrogen production, which may improve symptoms of endometriosis.

Menstrual disorders

Megestrol can be used to treat menstrual disorders such as abnormal uterine bleeding. It helps regulate the menstrual cycle by modulating hormones.

Endometrial thinning

Prior to endometrial ablation, a procedure that destroys the lining of the uterus, megestrol may be used to help thin the endometrial lining. This can improve results from the ablation procedure.

Male hormonal disorders

In men, megestrol may be used to treat conditions caused by hormonal imbalances, such as inoperable prostate cancer. It works by reducing testosterone levels.

How does megestrol work?

Megestrol is a synthetic progestin, meaning it mimics the effects of the hormone progesterone in the body. Some of the main ways megestrol works include:

  • Decreasing testosterone production in men
  • Suppressing estrogen production in women
  • Modulating the release of certain hormones from the pituitary gland
  • Binding to progesterone receptors to exert progestogenic effects
  • Increasing appetite by stimulating neuropeptide Y production

Through these mechanisms, megestrol can help slow cancer growth, regulate the menstrual cycle, improve endometriosis, stimulate appetite, and more.

What are the uses of megestrol for cancer?

Some of the cancer-related uses of megestrol include:

Breast cancer

Megestrol may be used to treat estrogen receptor-positive breast cancer in postmenopausal women. It appears to help slow down cancer cell growth and progression.

Endometrial cancer

Megestrol is sometimes used to treat endometrial cancer, especially in cases where progesterone therapy is deemed beneficial.


Megestrol is very effective at treating cachexia and anorexia associated with cancer. It helps stimulate appetite and prevent muscle wasting and severe weight loss.

Male cancers

In men, megestrol may be used to treat hormone-sensitive cancers like prostate cancer. It can help lower testosterone levels that may be fueling cancer growth.

So in summary, megestrol is most commonly used for appetite stimulation in cancer cachexia, but it also has direct anti-cancer effects for certain hormone-sensitive cancers.

What are the non-cancer uses of megestrol?

Some of the uses of megestrol unrelated to cancer include:


Megestrol is effective at reducing symptoms of endometriosis, including pelvic pain, by suppressing estrogen production.

Menstrual disorders

It can regulate menstrual cycles in cases like abnormal uterine bleeding. Megestrol helps stabilize the endometrium.

Appetite stimulation

Megestrol is widely used to treat anorexia, cachexia, and unexplained weight loss in people with HIV/AIDS, kidney disease, and elderly patients.

Endometrial thinning

It may be used prior to procedures like endometrial ablation to thin the lining for optimal results.

Male hormonal disorders

Megestrol can treat issues like hypogonadism or inoperable prostate cancer by reducing testosterone levels.

Female hormonal disorders

It can help treat conditions related to estrogen excess like precocious puberty or uterine bleeding.

So in summary, megestrol has many hormonal and appetite-related uses beyond cancer treatment.

What are the side effects of megestrol?

Some potential side effects of megestrol include:

  • Weight gain
  • Water retention
  • Swollen feet or legs
  • Increased blood sugar
  • Diarrhea or constipation
  • Dizziness
  • Headache
  • Weakness
  • High blood pressure
  • Nausea

Megestrol may also increase the risk for pneumonia, thrombosis, and certain cancers. Patients on megestrol should be monitored closely by a healthcare provider for side effects.

Is megestrol contraindicated in pregnancy?

Yes, megestrol is typically contraindicated in pregnant women. Megestrol has been assigned to pregnancy category D by the FDA.

Animal studies have shown increased risks and adverse events when megestrol is administered during pregnancy. Megestrol may cause fetal harm and congenital anomalies if used during pregnancy. It is recommended that pregnant women avoid megestrol unless the benefit clearly outweighs the risk.

How does megestrol compare to other appetite stimulants?

Drug Mechanism Side Effects
Megestrol Stimulates neuropeptide Y Weight gain, edema, thrombosis
Dronabinol Cannabinoid receptors Dizziness, dysphoria
Mirtazapine Antihistamine, 5-HT receptors Fatigue, increased appetite
Oxandrolone Androgen receptors Liver toxicity, masculinization

Compared to other appetite stimulants like dronabinol, mirtazapine, and oxandrolone, megestrol is very effective but tends to cause more significant weight gain and fluid retention. However, it does not cause the psychoactive effects of dronabinol or the liver toxicity associated with oxandrolone. Megestrol is especially useful in cancer cachexia and HIV/AIDS wasting.

What are common dosage forms of megestrol?

Megestrol is available in the following dosage forms:

  • Tablet: 20mg, 40mg, 80mg, 160mg tablets
  • Oral suspension: 40mg/mL suspension
  • Nanocrystal dispersion: 125mg/mL oral suspension

The most commonly prescribed formulation is the 20mg and 40mg tablets. The suspension forms are sometimes used if patients have difficulty swallowing pills.

What are typical dosing guidelines for megestrol?

The typical megestrol dosage ranges are:

  • Appetite stimulation: 400-800 mg/day
  • Weight loss related to cancer: 160-320 mg/day
  • Endometrial cancer: 40-320 mg/day
  • Endometriosis: 40-400 mg/day
  • Uterine bleeding: 40-400 mg/day

Lower doses around 40-160 mg/day are usually appropriate for hormonal issues, while higher doses of 400-800 mg/day are used for appetite stimulation and cancer cachexia. The maximum approved dose is 800 mg/day.

How long does it take for megestrol to work?

Patients typically begin to notice increased appetite anywhere from 3 days to 2 weeks after starting megestrol. However, maximum effects on weight gain may take 6 to 8 weeks to develop.

For cancer treatment, it may take up to 12 weeks on the medication to properly evaluate its efficacy. Hormonal effects like reduced testosterone or regulated menstruation happen more quickly within 1 to 2 weeks.

So while some effects are seen within days to weeks, the full therapeutic response requires 1-2 months of continued use in most cases.

Does megestrol interact with any medications?

Some important megestrol drug interactions include:

  • Anticoagulants like warfarin – megestrol can increase bleeding risk
  • Diabetes medications – megestrol can affect blood sugar control
  • CYP3A4 inducers like carbamazepine – can reduce megestrol levels
  • Hormonal contraceptives – increased risk for thromboembolism

Megestrol is also highly protein-bound and can interact with other protein-bound drugs such as NSAIDs, sulfonylureas, or hydantoins. Patients on megestrol should be monitored for reduced efficacy or increased side effects of interacting medications.

Is megestrol safe for long-term use?

There is limited data on the long-term safety of megestrol beyond 2 years of continual use. Potential risks with long-term therapy include:

  • Nutritional deficiencies
  • Adrenal insufficiency
  • Increased bone fractures
  • Metabolic effects like hyperglycemia
  • Cardiovascular side effects
  • Thromboembolic events

Periodic breaks from megestrol therapy may be beneficial in some patients to reduce adverse events. Nutritional status, bone health, glucose control, and cardiovascular risk factors should be monitored. The lowest effective dose should be used long-term.

What precautions should be taken with megestrol?

Some precautions to consider with megestrol use include:

  • May cause fetal harm – avoid in pregnancy
  • Can worsen diabetes – monitor blood sugar
  • Increases thrombosis risk – avoid in hypercoagulable disorders
  • Suppresses adrenal function – avoid abrupt discontinuation
  • May increase risk of osteoporosis and fractures
  • Can lower testosterone levels in men – supplement with testosterone if indicated

Megestrol has a significant side effect profile that requires proper precautions and monitoring by the prescribing physician. It should be avoided in pregnancy and used judiciously in high-risk patients.

What signs of toxicity should be monitored with megestrol use?

Signs of megestrol toxicity to be aware of include:

  • Nausea, vomiting, diarrhea
  • Yellow skin or eyes, pale stools – may indicate liver injury
  • Bleeding, bruising, petechiae – may indicate thrombocytopenia
  • Heart palpitations, dizziness – may indicate arrhythmia
  • Confusion, headache, seizures – may indicate adrenal crisis
  • Shortness of breath, chest pain – may indicate thromboembolism

Routine lab monitoring including liver function tests, electrolytes, blood counts, and urinalysis may help detect toxicity. Toxicity can often be managed by dose reduction or discontinuation along with symptomatic treatment.

Who should not take megestrol?

Megestrol is contraindicated in the following patients:

  • Pregnant women – can cause fetal harm
  • Breastfeeding women – excreted into breastmilk
  • Hypersensitivity to megestrol or any components
  • Undiagnosed vaginal bleeding – megestrol prevents diagnostic measures
  • Active thromboembolic disease – increases thrombosis risk

It should also be avoided in patients at high risk for thromboembolic events, adrenal insufficiency, osteoporosis, endocrine abnormalities like Cushing’s syndrome, and other conditions that may be exacerbated by megestrol.

Is megestrol approved for use in children?

No, megestrol has not been approved for use in pediatric populations. The safety and efficacy in children have not been established. Use of megestrol in children should be decided carefully by the physician based on a benefit-risk assessment for the individual patient.

Does megestrol cause weight gain?

Yes, weight gain is a very common side effect of megestrol therapy. Megestrol can lead to increased appetite, water retention, fat deposits, and muscle wasting prevention – all of which may result in dramatic weight gain.

In one study, over 90% of people taking megestrol experienced significant weight gain of 10% or more from their baseline weight. The average gain was 18% from baseline.

While the weight gain can be beneficial for cancer cachexia and wasting, cosmetic weight gain may be undesirable in some patients. Adjusting the dosage can help manage the degree of weight gain in some cases.

Can you get pregnant while taking megestrol?

Getting pregnant while taking megestrol is strongly discouraged. Animal studies show megestrol is associated with reproductive toxicity and congenital malformations in fetuses. There is also a risk for masculinization of the female fetus.

For women of childbearing age using megestrol, a non-hormonal contraceptive method is recommended to prevent pregnancy. Patients should notify their doctor immediately if pregnancy does occur. The risks and benefits of continuing the pregnancy should be carefully evaluated.

Does megestrol affect testosterone levels in men?

Yes, megestrol can significantly decrease testosterone production in men. This relates to its side effect of reduced libido and impotence in some male patients.

One study found that 800 mg/day of megestrol for 12 weeks reduced mean testosterone levels by 46% compared to baseline in men. Testosterone reduction may be beneficial for conditions like prostate cancer but undesirable for otherwise healthy men.

Hormone levels and testosterone-related side effects should be monitored in men on megestrol therapy. Testosterone supplementation may be warranted based on the clinical situation.


In summary, megestrol is a progestin medication used primarily for appetite stimulation, cancer treatment, and hormonal disorders. It works by decreasing sex hormones, modifying cortisol and testosterone, and increasing neuropeptide Y levels. While it can be effective for conditions like cachexia and endometriosis, megestrol has a significant side effect profile that warrants close monitoring and follow-up testing.

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