What is Mifepristone?
Mifepristone (formerly known as RU-486) is a medication that blocks the action of the hormone progesterone. Progesterone is needed to sustain a pregnancy. Mifepristone has been used, in combination with other medications called prostaglandins, for medical abortion since 1988 in France and China, and since the early 1990’s in the United Kingdom and Sweden. It has been licensed for use in 37 countries including the United States where it was approved in September 2000. Millions of women worldwide have safely used mifepristone regimens to end their pregnancies.
How mifepristone works to end pregnancy
Mifepristone blocks the action of progesterone, which is needed to sustain a pregnancy. This results in:
Changes in the uterine lining and detachment of the pregnancy
Softening and opening of the cervix
Increased uterine sensitivity to prostaglandin
In the U.S., mifepristone is used in combination with another medication, a synthetic prostaglandin called misoprostol. Misoprostol causes the uterus to contract, and helps the pregnancy tissue to expel.
How effective is the combination of mifepristone and misoprostol in terminating an early pregnancy?
Depending on the prescribing physician’s protocols, mifepristone and misoprostol can be used for early abortion up to 63 days after the start of the last menstrual period. Approximately 95-98% of women will have a complete abortion when using mifepristone/misoprostol. Success rates may depend on the treatment regimen and the duration of the pregnancy. The remaining women will need a suction procedure, either because of ongoing or excessive bleeding, an incomplete abortion (tissue remains in the uterus but there is no growing embryo), or an ongoing pregnancy (a viable growing pregnancy, which occurs in less than 1% of cases).
Treatment regimen with mifepristone/misoprostol
Clinical studies have shown that several variations in mifepristone/misoprostol treatment regimens are safe and effective. Generally, however, once a woman has decided to have a medical abortion, there are three steps in the process of a medical abortion:
Step One (at the medical office or clinic)
A medical history is taken and a clinical exam and lab tests are performed.
Counseling is completed and informed consent is obtained.
If eligible for medical abortion, the woman swallows the mifepristone pill(s).
Step Two (at the office/clinic or at home depending on the treatment regimen)
This step takes place within about 2 days of step one.
Unless abortion has occurred and has been confirmed by the clinician, the woman uses misoprostol. Misoprostol tablets may be swallowed, placed between cheek and gum, or inserted into the vagina, depending on the treatment regimen.
Step Three (at the office or clinic)
This step takes place within about 2 weeks of step two.
The clinician evaluates the woman to confirm a complete abortion. It is essential for women to return to the office/clinic to confirm that the abortion is complete.
If there is an ongoing pregnancy, a suction abortion should be provided.
If there is an incomplete abortion, the clinician will discuss possible treatment options with the woman. These may include waiting and re-evaluating for complete abortion in a number of days or performing a suction procedure.
Possible side effects of a mifepristone abortion
Side effects, such as pain, cramping and vaginal bleeding, result from the abortion process itself, and are therefore expected with a medical abortion. Other side effects may include nausea, vomiting, diarrhea, chills, or fever. Complications are rare, but may include infection, excessive vaginal bleeding requiring transfusion (occurs in approximately 1 in 500 cases), incomplete abortion or ongoing pregnancy which requires a suction abortion (see above). In exceedingly rare instances, as with miscarriage, suction abortion and childbirth, death may occur. Reports of death after medical abortion are very rare – less than 1 in 100,000 cases – a rate comparable to that for early surgical abortion and for miscarriage.1
What women can expect from a mifepristone abortion
Medical abortion with mifepristone/misoprostol requires at least two visits to a medical office or clinic.
Following established treatment regimens, approximately 95-98% of women using mifepristone/misoprostol will have a complete medical abortion.
Complete abortion generally occurs more quickly when misoprostol is used vaginally rather than orally.
In most cases, bleeding will begin within several hours of using vaginal misoprostol.
Approximately two-thirds of women will have a complete medical abortion within 4 hours of using oral misoprostol.
Approximately 90% of women will have a complete medical abortion within 24 hours of using oral misoprostol.
On average, women may expect to have bleeding and/or spotting for 9-16 days.
Women may pass clots, ranging in size.
Some women may see whitish pregnancy tissue.
If the medications fail to end the pregnancy, a suction abortion should be provided. For this reason, a woman who chooses medical abortion must be willing to have a suction abortion if needed.
First-Trimester Abortion: A Comparison
Procedure 1: Mifepristone
How it Works: Mifepristone, taken orally, blocks the action of progesterone, which causes the uterine lining to thin and the pregnancy to detach. It also causes the cervix to soften and dilate, and increases the production of prostaglandins, which cause uterine contractions. Misoprostol, a prostaglandin analogue taken either orally or inserted vaginally within a few days of mifepristone, induces uterine contractions and increases the effectiveness of mifepristone to approximately 95-98%.
Advantages: – Usually avoids the use of surgical instruments, thus avoiding the risk of injury to the cervix or uterus from instrumentation.- Anesthesia not required.- High success rate (95-98%).- Resembles a “natural miscarriage.”- May offer women more privacy.- Both drugs can be administered orally.- Can be used very early in pregnancy.- Procedure completed within 24 hours of the misoprostol administration in 90% of women.- Approved by the FDA for early abortion.
Disadvantages: – Requires at least 2 visits.- Effectiveness decreases with use after 7 weeks in regimens using oral misoprostol. Efficacy remains high up to 9 weeks with vaginal misoprostol.- Takes days or, rarely, weeks to complete.- Post-procedure bleeding may last longer than with surgical abortion.- Women may see blood clots and pregnancy tissue.
Procedure 2: Methotrexate
How it Works: Methotrexate, given by injection, or occasionally orally, stops the ongoing process of implantation of an early pregnancy. Misoprostol, a prostaglandin analogue inserted vaginally several days after the methotrexate, causes uterine contractions and increases the effectiveness of methotrexate to approximately 95%.
Advantages:– Usually avoids the use of surgical instruments, thus avoiding the risk of injury to the cervix or uterus from instrumentation.- Anesthesia not required.- High success rate up to 7 weeks (95%).- Resembles a “natural miscarriage.”- May offer women more privacy.- Can be used very early in pregnancy.- Can be used to treat ectopic pregnancy.- Methotrexate and misoprostol are both FDA-approved for other uses.
Disadvantages:– Requires at least 2 visits.- Effectiveness decreases with use after 7 weeks.- May require several doses of misoprostol.- Takes several days or weeks to complete.- Post-procedure bleeding may last longer than with surgical abortion.- Women may see blood clots and pregnancy tissue.
Procedure 3: Vacuum Aspiration
How it Works: Cervix is gradually opened with tapered rods. A cannula (straw-like tube), which is attached to a suction apparatus (either an electric machine or hand-held syringe), is inserted through the cervix into the uterus. The contents of the uterus are emptied by suction. Vacuum aspiration is approximately 99% effective.
Advantages:– Usually only requires one visit to the provider.- Procedure is usually completed within minutes.- Allows for sedation if desired.- High success rate (approximately 99%).- Can be used early in pregnancy.
Disadvantages:– Involves a surgical procedure.- May seem less private to some women than aborting at home.