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Overview: Mifepristone is an oral tablet used to treat high blood sugar in certain people with Cushing’s syndrome. Mifepristone works by blocking the effects of certain hormones. Common side effects include low appetite, joint pain, fluid retention, and high blood pressure. Serious side effects may include vaginal bleeding, adrenal gland problems, heart rhythm changes, and pneumonia.

Uses

What is mifepristone used for?

Mifepristone is commonly used to treat high blood sugar in certain people who have Cushing’s syndrome and type 2 diabetes or problems with blood sugar (glucose intolerance).

Mifepristone may also be used for other conditions as determined by your healthcare provider.

See also: Mifepristone (Mifeprex)

How does mifepristone work (mechanism of action)?

Mifepristone works by blocking the effects of certain hormones. At lower doses, it blocks progesterone, a hormone needed for pregnancy to continue. At higher doses, mifepristone also blocks the effects of cortisol, the stress hormone. This helps lower blood sugar in people with Cushing’s syndrome.

How is mifepristone supplied (dosage forms)?

Brands and other names

  • Korlym

Dosage forms and strengths

  • 300 mg oral tablets

How should I store mifepristone?

Mifepristone should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of mifepristone?

The most common side effects of mifepristone are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Nausea or vomiting
  • Tiredness
  • Headache
  • Low potassium levels (see below)
  • Joint pain
  • Fluid buildup in your hands, legs, ankles, or feet
  • High blood pressure
  • Dizziness
  • Low appetite
  • Vaginal bleeding (see below)

There may be other side effects of mifepristone that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of mifepristone?

While less common, the most serious side effects of mifepristone are described below, along with what to do if they happen.

Severe Allergic Reactions. Mifepristone may cause allergic reactions, which can be serious. Stop taking mifepristone and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Low Potassium Levels (Hypokalemia). Mifepristone can cause a low potassium level, which can be serious and may lead to death. Your healthcare provider may check your potassium levels, especially if you take certain other medicines. Keep all appointments to have your blood checked. Call your healthcare provider if you have any of the following symptoms of a low potassium level.

  • Muscle cramps or twitching
  • Constipation
  • Feeling unusually weak or tired 

Reduced Adrenal Function. Mifepristone may cause your body’s adrenal glands to stop making as much cortisol (the stress hormone). This is known as adrenal insufficiency. Tell your healthcare provider if you have any of the following symptoms of adrenal insufficiency.

  • Nausea
  • Feeling weak or more tired than usual
  • Low blood pressure or dizziness
  • Low blood sugar

Vaginal Bleeding. Mifepristone causes hormone changes that can lead to thickening of the lining of the uterus (endometrium) and vaginal bleeding. The risk may be higher in people with bleeding disorders or those taking blood thinner medicines. Tell your healthcare provider if you have changes in your periods or menstrual cycle, or if you have vaginal bleeding that is different than usual while taking mifepristone.

Heart Rhythm Changes. Mifepristone may cause a rare, dangerous heart rhythm problem called QT prolongation. The risk may be higher in people taking other medicines that can also cause this heart rhythm change. Tell your healthcare provider right away if you faint or have changes in your heart rate or rhythm, such as a fast or skipping heartbeat.

Pneumonia. Some people may develop pneumonia after starting mifepristone. Pneumonia is an infection of the lungs that can make it hard to breathe. Contact your healthcare provider right away if you have shortness of breath, cough,  fever, or increased mucus while taking mifepristone.

Warnings & Precautions

Who should not use mifepristone?

Allergies to Ingredients. People who are allergic to any of the following should not take mifepristone.

  • Mifepristone
  • Korlym
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific mifepristone products they stock.

Pregnancy. Do not take mifepristone if you are pregnant. If you become pregnant, contact your healthcare provider right away. See the Pregnancy section for more details. 

Drug Interactions. Mifepristone should not be taken while you are using certain other medicines. Before taking mifepristone, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Endometrial Problems. Mifepristone blocks the hormone progesterone, which is important for maintaining the lining of the uterus (endometrium). People with the following conditions should not take mifepristone because it can make symptoms worse and increase the risk of vaginal bleeding.

What should I know about mifepristone before taking it?

Do not take mifepristone unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share mifepristone with other people, even if they have the same condition as you. It may harm them.

Keep mifepristone out of the reach of children.

Do not chew, cut, or crush mifepristone. Swallow it whole.

What should I tell my healthcare provider before taking mifepristone?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if mifepristone is right for you.

In particular, make sure that you discuss any of the following.

Other Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • Liver or kidney problems
  • Heart problems, such as heart failure, coronary artery disease, or an abnormal heart rate or rhythm
  • Bleeding problems
  • Low potassium in your blood
  • Organ transplant
  • Thyroid problems

Pregnancy. Mifepristone may cause harm to an unborn baby. You must not be pregnant when you start mifepristone. If you can become pregnant, use a nonhormonal birth control method, such as condoms, while taking mifepristone and for one month after your last dose. Talk with your healthcare provider about what birth control options are right for you. Tell your healthcare provider if you are or plan to become pregnant.

For information about a different form of mifepristone that may be prescribed to end a pregnancy, see: Mifepristone (Mifeprex).

Breastfeeding. Mifepristone passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take mifepristone while breastfeeding.

Interactions

Does mifepristone interact with foods or drinks?

Take mifepristone with a meal. Taking every dose with food helps the medicine work the way it should.

Grapefruit can increase the levels of mifepristone in your body, which may raise the risk of side effects. Avoid grapefruit and grapefruit juice while taking mifepristone.

It is unknown if drinking alcohol will affect mifepristone. The risk of nausea, vomiting, or bleeding may be increased if you drink alcohol with mifepristone.

Does mifepristone interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking mifepristone.

  • A statin, such as simvastatin (Zocor) or lovastatin (Altoprev), which is a medicine used to lower cholesterol
  • A corticosteroid, such as dexamethasone, methylprednisolone, or prednisone, which is a medicine for certain inflammatory conditions
  • Fentanyl, which is an opioid medicine used to treat certain types of pain
  • A medicine used to help the body accept a new organ after an organ transplant
  • A birth control pill, patch, vaginal ring, implant, injection, or intrauterine device (IUD)
  • A medicine used for fungal infections, such as ketoconazole, itraconazole (Sporanox, Tolsura), posaconazole (Noxafil), or fluconazole (Diflucan)
  • A nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen, naproxen, and others, which is in many prescription and OTC products for pain, swelling, and fever
  • A medicine for seizures, such as carbamazepine, phenytoin, or phenobarbital 
  • A blood thinner, which is a medicine used to treat or prevent blood clots
  • St. John’s wort, which is a supplement that may be used for depression
  • A medicine for HIV, AIDS, or hepatitis C
  • Bupropion (Wellbutrin SR, Wellbutrin XL, Aplenzin, and others), which is a medicine used to treat depression or to help quit smoking
  • Rifampin (Rifadin) or rifapentine (Priftin), which is a medicine commonly used to treat an infection called tuberculosis
  • An ergot, such as ergotamine (Ergomar) or dihydroergotamine (Migranal or Trudhesa), which is a medicine used to treat migraine

Many other medicines may alter the blood levels of mifepristone, and vice versa. Tell your healthcare provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with mifepristone. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much mifepristone?

If you or someone else has taken too much mifepristone, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of mifepristone?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses. 

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