Megestrol belongs to a group of medications known as progestogens. Megestrol is used to treat prostate cancer because testosterone is needed by prostate cancer cells for growth. It prevents the release of a hormone required for production of testosterone in the testicles.

Megestrol also slows the growth of breast and endometrium (lining of the uterus) cancer cells by interfering with other hormones and proteins that are required for growth of the cancer cells. It is also used to treat appetite loss and severe weight or muscle loss in people with cancer. It helps by promoting the production of certain proteins that increase appetite and weight gain.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended dose depends on the condition being treated and body weight.

For people with prostate cancer, the recommended dose is 120 mg taken as a single daily dose in combination with diethylstilbestrol 0.1 mg.

For people with breast cancer, the usual dose is 160 mg daily. This dose may be divided into 4 equal doses of 40 mg.

For people with cancer of the endometrium, the usual dose is 80 mg to 320 mg daily, which can be divided into 40 mg tablets taken 2 to 4 times daily, or 160 mg tablets taken 1 to 2 times daily.

For people with cancer and appetite loss, muscle wasting, or significant weight loss, the usual adult dose is 400 mg to 800 mg as a single daily dose.

The effectiveness of megestrol acetate can be assessed after 2 months have passed following the start of therapy.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

Megestrol can be taken with or without food.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature in a cool, dry place.

Do not take megestrol if you:

• are allergic to megestrol acetate or any ingredients of the medication
• are or may be pregnant (first 4 months)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• diarrhea
• hair loss
• increased appetite
• mild blood pressure increase
• mood changes
• nausea or vomiting
• swelling of the face, ankles, or feet
• weight gain

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• breast enlargement
• changes in vaginal bleeding
• decreased hearing
• decreased interest or ability in sexual activity
• depression
• filling or rounding out of face
• hot flushes
• impotence
• increased flow of breast milk
• increased urination
• loss of appetite
• mood changes
• rash
• shortness of breath
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• unusual tiredness or weakness

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of stroke (e.g., sudden or severe headache; sudden loss of coordination; vision changes; sudden slurring of speech; or unexplained weakness, numbness, or pain in arm or leg)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Blood clots: This medication may increase the chance of blood clot formation, which will cause blood flow to organs or to the extremities to be reduced.

If you have a history of clotting, you may be at increased risk of experiencing blood clot-related problems such as heart attack, stroke, or clots in the deep veins of your leg. Discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you experience symptoms such as sharp pain and swelling in the leg, difficulty breathing, chest pain, blurred vision or difficulty speaking, contact your doctor immediately.

Diabetes: Megestrol acetate may cause a loss of control of diabetes by increasing blood sugar levels and changing glucose tolerance. If you have diabetes, you may find it necessary to monitor your blood sugar more frequently while using this medication.

If you have diabetes or are at risk for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. You may need to check your blood glucose levels more often.

Kidney disease: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have kidney problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

Osteoporosis: Long-term use of this medication can increase the risk of osteoporosis (brittle bones). Talk to your doctor about ways to help prevent osteoporosis. Your doctor will monitor your bone density if you take this medication for a long period of time.

Pregnancy: Megestrol acetate is not recommended for use during the first 4 months of pregnancy. Women should use effective birth control when taking megestrol. If you become pregnant while taking megestrol, tell your doctor right away.

Breast-feeding: This medication may pass into breast milk. If you are a breast-feeding mother and are taking megestrol acetate, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

There may be an interaction between megestrol acetate and any of the following:

• bromocriptine
• diabetes medications (e.g., acarbose, canagliflozin, glyburide, insulin, linagliptin, lixisenatide, metformin, rosiglitazone)
• testosterone and androgens (for men taking megestrol to treat prostate cancer)
• estrogen (for women taking megestrol for breast or endometrial cancer)
• ulipristal
• warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.