Mifepristone

Pronunciation: miff-ee-pris-tone
Generic name: mifepristone
Brand names: Mifeprex, Korlym
Dosage form: oral tablet
Drug classes: Progesterone receptor modulators, Uterotonic agents

Medically reviewed by Carmen Pope, BPharm. Last updated on May 24, 2024.

What is mifepristone?

Mifepristone is an oral cortisol receptor blocker/progestin antagonist that has two main uses:

• In combination with misoprostol to end an early pregnancy when it has been 70 days or less since the first day of a patient’s last menstrual period (10 weeks or less)(Mifeprex brand and generic mifepristone)
• To treat high blood sugar (hyperglycemia) caused by high cortisol levels in the blood (hypercortisolism) in adults with endogenous Cushing’s syndrome who have type 2 diabetes mellitus or glucose intolerance and have failed surgery or cannot have surgery (Korlym brand).
  • For this use, mifepristone is given daily, and females must avoid becoming pregnant.
  • Mifepristone is not for use in people with type 2 diabetes mellitus that is not caused by Cushing’s syndrome.

Using mifepristone with misoprostol is termed a medical abortion. 

• Although FDA regulations allow certified healthcare professionals and pharmacies to dispense mifepristone and misoprostol for medical abortion both in healthcare facilities and by telehealth and mail, certain state laws may not allow this. For example, Louisiana has passed a bill that classifies mifepristone and misoprostol as dangerous controlled substances which, once signed, would mean anyone possessing these abortion pills without a prescription could face jail time and fines. Most abortions are already illegal in Louisiana.

Mifepristone selectively blocks progesterone via the progesterone receptor at low doses and cortisol via the glucocorticoid receptor at high doses.  

• When used to terminate a pregnancy, mifepristone works by competing with progesterone at progesterone-receptor sites. This blocks the activity of naturally occurring progesterone, resulting in effects on the uterus and cervix that, when combined with misoprostol, result in the termination of an intrauterine pregnancy by sensitizing the lining of the uterus to the contraction-inducing activity of prostaglandins.
• When used to treat Cushing’s syndrome, it competes with cortisol to bind to the cortisol receptor, which leads to decreased cortisol activity without a decrease in cortisol levels. This can lead to decreases in blood sugar levels, weight loss, and a reduction in the amount of antidiabetic medications required.

Mifepristone was first FDA-approved on September 28, 2000, as the brand Mifeprex. Korlym was FDA-approved on February 17, 2012.

Related/similar drugs

dexamethasone, Decadron, cyproheptadine, oxytocin, Pitocin, Hemabate, carboprost

Mifepristone side effects

When mifepristone is used to terminate a pregnancy

Mifepristone may cause serious side effects, such as serious infection, heavy bleeding, and abdominal pain (see warnings below)

Cramping and vaginal bleeding are expected with this treatment. Usually, these symptoms mean that the treatment is working. But sometimes you can get cramping and bleeding and still be pregnant. This is why you must follow up with your healthcare provider approximately 7 to 14 days after taking mifepristone and misoprostol.

• If you are not already bleeding after taking mifepristone, you probably will begin to bleed once you take misoprostol, the medicine you take 24 to 48 hours after mifepristone.
• Bleeding or spotting can be expected for an average of 9 to 16 days and may last for up to 30 days.
• Your bleeding may be similar to, or greater than, a normal heavy period. You may see blood clots and tissue. This is an expected part of passing the pregnancy.

The most common side effects reported when mifepristone is used to terminate a pregnancy affecting 15% or more women are nausea, weakness, fever/chills, vomiting, headache, diarrhea, and dizziness.

These are not all the possible side effects of mifepristone when used to terminate a pregnancy. Call your healthcare provider for medical advice about any side effects that bother you or do not go away. You may report side effects to the FDA at 1-800-FDA-1088.

When mifepristone is used to treat Cushing’s syndrome

Mifepristone can cause serious side effects when taken daily to treat Cushing’s syndrome, such as pregnancy loss, adrenal insufficiency, low potassium, vaginal bleeding, menstrual cycle changes, QT interval prolongation, and a deterioration in other conditions treated by corticosteroids (see warnings below).

The most common side effects of daily mifepristone in people with Cushing's syndrome affecting 20% or more people include:

• nausea or vomiting
• fatigue
• headache
• low potassium in your blood
• pain in your arms and legs (arthralgia)
• swelling of your arms and legs (peripheral edema)
• high blood pressure
• dizziness
• decreased appetite
• thickening of the lining of the uterus (endometrial hypertrophy).

Tell your doctor if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of mifepristone. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Warnings

Pregnancy termination

Serious side effects reported in females taking mifepristone and misoprostol to terminate a pregnancy include:

Serious infection that has resulted in death has occurred in a very small number of cases although it is not clear if mifepristone and misoprostol were the cause. Contact your healthcare provider right away if you have any of the following:

• Heavy bleeding, especially if you bleed enough to soak through two thick full-size sanitary pads per hour for two consecutive hours or if you are concerned about heavy bleeding. In about 1 out of 100 women, bleeding can be so heavy that it requires a surgical procedure (surgical aspiration or D&C).
• Abdominal pain, abdominal discomfort, or “feeling sick”, including weakness, nausea, vomiting, or diarrhea, with or without fever, more than 24 hours after taking mifepristone. These symptoms may be a sign of a serious infection or another problem (including an ectopic pregnancy, a pregnancy outside the womb)
• A high fever (100.4°F or higher) that lasts for more than 4 hours. Fever may be a symptom of a serious infection or another problem.

If you cannot reach your healthcare provider for any of these problems, go to the nearest hospital emergency room. Take your mifepristone (Mifeprex) Medication Guide with you or tell them that you have recently taken medicine to terminate a pregnancy.

Rhesus immunization. Using mifepristone requires the same preventive measures as those taken before and during surgical abortion to prevent rhesus immunization.

Cushing's syndrome

Serious side effects reported in people with Cushing’s syndrome taking daily mifepristone include:

Pregnancy loss. When used for non-pregnancy related conditions, such as for Cushing’s syndrome, mifepristone should not be used during pregnancy, and women who can become pregnant must:

• have a negative pregnancy test before starting mifepristone or before restarting it if you stopped taking it for more than 14 days
• use a non-hormonal form of birth control while taking mifepristone and for 1 month after stopping it.

Reduced effects of adrenal hormones (adrenal insufficiency). Long-term use of mifepristone stops an adrenal hormone in your body called cortisol from working. Tell your doctor right away if you have any symptoms of adrenal insufficiency. Symptoms may include:

• unusual tiredness or weakness
• nausea
• fatigue
• low blood pressure (hypotension)
• low blood sugar (hypoglycemia).

Low blood potassium (hypokalemia). Your doctor should check the potassium level in your blood before you start taking mifepristone and while you take it. Tell your doctor if you have any signs of low potassium. Signs may include muscle weakness, aches, cramps, or abnormal or irregular heartbeats (palpitations).

Vaginal bleeding. Long-term mifepristone may cause the lining of your uterus to become thick and may cause your uterus to bleed. Tell your doctor right away about any bleeding from your vagina that is not normal for you.

Disruption of the menstrual cycle. Your periods may be longer or shorter than usual and you may experience more blood loss.

Problems with the electrical system of your heart (QT interval prolongation).

Worsening symptoms of other medical problems that are being treated with corticosteroids when you take corticosteroids and mifepristone at the same time. Mifepristone antagonizes the effects of corticosteroids.

When used for a medical abortion, mifepristone is not approved for ending pregnancies that are further along than 10 weeks.

Before taking mifepristone

Pregnancy termination

Some women should not take mifepristone (Mifeprex) to terminate a pregnancy, including women who:

• have a pregnancy that is more than 70 days (10 weeks). Your healthcare provider may do a clinical examination, an ultrasound examination, or other testing to determine how far along you are in pregnancy
• are using an IUD (intrauterine device or system). It must be taken out before you take mifepristone 
• have been told by your healthcare provider that you have a pregnancy outside the uterus (also called an ectopic pregnancy)
• are allergic to mifepristone, misoprostol, Mifeprex, Korlym, Cytotec, or Arthrotec
• have problems with their adrenal glands (chronic adrenal failure).
• take a medicine to thin your blood, such as dabigatran or warfarin
• have a bleeding problem
• have porphyria
• take certain steroid medicines.

Tell your healthcare provider if you:

• cannot follow up within approximately 7 to 14 days of your first visit
• are breastfeeding
• are taking medicines, including prescription and over-the-counter medicines, vitamins, and herbal supplements (see interactions below).

Ask your healthcare provider if you are not sure about all your medical conditions before taking mifepristone.

Cushing’s syndrome

Do not take mifepristone if you:

• are allergic to mifepristone or any of the inactive ingredients in Korlym (see ingredients below)
• are pregnant
• are taking certain medications such as statins, cyclosporine, ergots, fentanyl, corticosteroids, and others (see interactions below)
• are a woman who still has her uterus (womb) and has unexplained bleeding from your vagina or known changes in the cells lining your uterus (endometrial hyperplasia) or cancer of the lining of your uterus (endometrial cancer).

Tell your healthcare provider if you:

• are pregnant or planning to become pregnant
• have low potassium in your blood (hypokalemia)
• have or have had a bleeding problem or are taking medicines to thin your blood
• have or have had heart problems
• have had an organ transplant
• have been taking medicines called corticosteroids (cortisone, dexamethasone, methylprednisolone, prednisolone, prednisone)
• are breastfeeding or planning to breastfeed.

Pregnancy

Mifepristone should not be used in women with Cushing’s syndrome who are pregnant because it will cause loss of the unborn baby. There is no data regarding the risk of birth defects in women who have inadvertently been exposed to mifepristone while pregnant.

If you can become pregnant, you will need to have a negative pregnancy test before starting this treatment and use a non-hormonal form of birth control while taking mifepristone and for 1 month after stopping it.

Talk to your doctor about how to prevent pregnancy. Tell your doctor right away if you think you may be pregnant.

Breastfeeding

Mifepristone can pass into your breast milk. The effect of the mifepristone on the breastfed infant or milk production is unknown.

How should I take mifepristone?

Take mifepristone exactly as your doctor tells you.

Pregnancy termination

The usual dosage for a medical abortion is 200 mg of mifepristone on Day 1, followed 24 to 48 hours later by 800 mcg misoprostol taken buccally (see below).

• The mifepristone tablet is swallowed whole.
• The misoprostol tablets are taken buccally. You put them between your top lip and gum (in your cheek pouch).
  • Place 2 misoprostol tablets in each cheek pouch for 30 minutes and then swallow anything left over with a drink of water or another liquid.
• The medicines may not work as well if you take misoprostol sooner than 24 hours after mifepristone or later than 48 hours after mifepristone.

Misoprostol often causes cramps, nausea, diarrhea, and other symptoms. Your healthcare provider may send you home with medicines for these symptoms.

• The pregnancy is likely to be passed from your uterus within 2 to 24 hours after taking the misoprostol tablets.
• When the pregnancy is passed from the uterus, you will have bleeding and cramping that will likely be heavier than your usual period.
• About 2 to 7 out of 100 women taking Mifeprex will need a surgical procedure because the pregnancy did not completely pass from the uterus or stop bleeding.
• Follow your healthcare provider's advice about what to do if you have severe side effects (see warnings above).

You will need to talk to a healthcare provider in 7 to 14 days for a follow-up assessment to confirm that the pregnancy has been terminated.

• Prolonged heavy vaginal bleeding is not proof of a complete abortion.
• If the treatment fails and the pregnancy continues, the risk of fetal malformation is unknown.
• It is recommended that ongoing pregnancy be managed by surgical termination.

Cushing’s syndrome

Mifepristone is usually taken 1 time each day.

• The usual starting dose is 300 mg by mouth (orally) once a day.
• Take with food.
• Swallow the tablets whole. Do not split, crush, or chew the tablets. If you cannot swallow the tablets whole, tell your doctor.
• Your healthcare provider may increase your dosage of mifepristone in 300mg increments every 2 to 4 weeks to a maximum daily dose of 1200 mg once a day (not exceeding 20 mg/kg a day or 600 mg/day for those with kidney or liver disease).

What should I avoid while taking mifepristone?

Do not drink grapefruit juice while you take mifepristone. Grapefruit juice may increase the amount of mifepristone in your blood and increase your risk of side effects.

What happens if I am still pregnant after taking mifepristone with misoprostol treatment?

If you are still pregnant, your healthcare provider will talk with you about a surgical procedure to end your pregnancy. In many cases, this surgical procedure can be done in the office/clinic. The chance of birth defects if the pregnancy is not ended is unknown.

Will I be able to get pregnant again after having a medical abortion?

There is no indication that taking mifepristone and misoprostol for a medical abortion will affect your future fertility and the ability to become pregnant, although animal studies have shown there may be some disruption to your menstrual cycle for up to 3 weeks after taking the combination.

Another pregnancy can occur following a medical abortion before your periods resume.

You can start using contraception as soon as the pregnancy expulsion has been confirmed, or before you resume sexual intercourse.

What other medications will affect mifepristone?

Tell your doctor about all of the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal supplements.

Using mifepristone daily (Korlym brand) with certain other medicines can affect each other. Especially tell your doctor if you take medicines to treat:

• fungal infections (such as ketoconazole)
• cyclosporine (Gengraf, Neoral, Restasis, Sandimmune)
• depression
• dihydroergotamine (Migranal) or ergotamine (Ergomar, Migergot)
• fentanyl (Abstral, Actiq, Duragesic, Fentora, Lazanda, Onsolis, Sublimaze, Subsys)
• HIV infection
• Hepatitis C infection
• certain bacterial infections
• high blood pressure
• hormonal contraceptives
• pimozide (Orap)
• quinidine (Nuedexta)
• sirloimus (Rapamune, Torisel) or tacrolimus (Prograf, Protopic)
• statin medications such as simvastatin (Zocor, Vytorin, Simcor) or lovastatin (Mevacor, Altoprev, Advicor)
• steroid medicines such as prednisone
• thyroid hormones.

Medications such as ketoconazole, nefazodone, ritonavir, and other strong CYP3A inhibitors may increase blood levels of mifepristone and should only be used together when necessary. A maximum dose of 900 mg of mifepristone should be adhered to. If a strong CYP3A inhibitor is started in a person already taking mifepristone, the dosage of mifepristone may need to be reduced.

Do not use mifepristone with CYP3A inducers, such as glucocorticoids, rifampin, carbamazepine, phenobarbital, phenytoin, and grapefruit juice.

Avoid the use of Q-T interval prolonging medications such as quinidine, procainamide, or sotalol.

CYP3A4 inhibitors or inducers may also affect mifepristone taken as part of a medical abortion regimen, with inhibitors increasing mifepristone concentrations and inducers lowering them. Use with caution. 

Ask your doctor or pharmacist for a list of these medicines if you are not sure. Know the medicines you take. Keep a list of them to show to your doctor and pharmacist. See the prescribing information for a full list of interactions.

Storage

Store mifepristone at room temperature, between 68°F to 77°F (20°C to 25°C).

Keep out of the reach of children.

Mifepristone ingredients

Mifeprex ingredients

Active ingredient: mifepristone 200mg

Inactive ingredients: colloidal silica anhydrous, corn starch, povidone, microcrystalline cellulose, and magnesium stearate.

Available as 200 mg tablets.

Korlym ingredients

Active ingredient: mifepristone 300mg

Inactive ingredients: silicified microcrystalline cellulose, sodium starch glycolate, hydroxypropyl cellulose, sodium lauryl sulfate, magnesium stearate, hypromellose, titanium dioxide, triacetin, D&C yellow 10 aluminum lake, polysorbate 80, and FD&C yellow 6 aluminum lake.

Available as 300 mg tablets.

Manufacturer

Mifeprex: Danco Laboratories, LLC.

Korlym: Corcept Therapeutics Incorporated.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer