February 6, 2016
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Mifeprex (RU486)

"Risk factors for repeat pregnancy terminations include teenage pregnancy, social deprivation, two or more previous live births or miscarriages at the time of the initial termination, and the use of posttermination contraception with implants and "...



Side Effects


The treatment procedure is designed to induce the vaginal bleeding and uterine cramping necessary to produce an abortion. Nearly all of the women who receive Mifeprex and misoprostol will report adverse reactions, and many can be expected to report more than one such reaction. About 90% of patients report adverse reactions following administration of misoprostol on day three of the treatment procedure. Those adverse events that occurred with a frequency greater than or equal to 1% in the U.S. and French trials are shown in Table 3.

Vaginal bleeding and uterine cramping are expected consequences of the action of Mifeprex as used in the treatment procedure. Following administration of mifepristone and misoprostol in the French clinical studies, 80 to 90% of women reported bleeding more heavily than they do during a heavy menstrual period (see WARNINGS, Vaginal Bleeding). Women also typically experience abdominal pain, including uterine cramping. Other commonly reported side effects were nausea, vomiting and diarrhea. Some adverse reactions reported during the four hours following administration of misoprostol were judged by women as being more severe than others: the percentage of women who considered any particular adverse event as severe ranged from 2 to 35% in the U.S. and French trials. After the third day of the treatment procedure, the number of reports of adverse reactions declined progressively in the French trials, so that by day 14, reports were rare except for reports of bleeding and spotting.

Table 3: Type of Reported Adverse Events Following Administration of Mifepristone and Misoprostol in the U.S. and French Trials* (percentages)

  U.S. Trials French Trials
Abdominal Pain (cramping) 96 NA
Uterine cramping NA 83
Nausea 61 43
Headache 31 2
Vomiting 26 18
Diarrhea 20 12
Dizziness 12 1
Fatigue 10 NA
Back pain 9 NA
Uterine hemorrhage 5 NA
Fever 4 NA
Viral infections 4 NA
Vaginitis 3 NA
Rigors (chills/shaking) 3 NA
Dyspepsia 3 NA
Insomnia 3 NA
Asthenia 2 1
Leg pain 2 NA
Anxiety 2 NA
Anemia 2 NA
Leukorrhea 2 NA
Sinusitis 2 NA
Syncope 1 NA
Endometritis/Salpingitis/Pelvic Inflammatory Disease 1 NA
Decrease in hemoglobin greater than 2 g/dL NA 6
Pelvic pain NA 2
Fainting NA 2
*Only adverse reactions with incidence 1% are included.

Postmarketing Experience

The following adverse reactions have also been reported during post-approval use of Mifeprex and misoprostol. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. No causal relationship between these events and Mifeprex and misoprostol has been established:

Allergic reaction (including rash, hives, itching), hypotension (including orthostatic), lightheadedness, loss of consciousness, post-abortal infection (including endomyometritis, parametritis), ruptured ectopic pregnancy, shortness of breath, and tachycardia (including racing pulse, heart palpitations, heart pounding).

Read the Mifeprex (mifepristone (ru486)) Side Effects Center for a complete guide to possible side effects


Although specific drug or food interactions with mifepristone have not been studied, on the basis of this drug's metabolism by CYP 3A4, it is possible that ketoconazole, itraconazole, erythromycin, and grapefruit juice may inhibit its metabolism (increasing serum levels of mifepristone). Furthermore, rifampin, dexamethasone, St. John's Wort, and certain anticonvulsants (phenytoin, phenobarbital, carbamazepine) may induce mifepristone metabolism (lowering serum levels of mifepristone).

Based on in vitro inhibition information, coadministration of mifepristone may lead to an increase in serum levels of drugs that are CYP 3A4 substrates. Due to the slow elimination of mifepristone from the body, such interaction may be observed for a prolonged period after its administration. Therefore, caution should be exercised when mifepristone is administered with drugs that are CYP 3A4 substrates and have narrow therapeutic range, including some agents used during general anesthesia.

Read the Mifeprex Drug Interactions Center for a complete guide to possible interactions

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 6/27/2008

Side Effects

Mifeprex - User Reviews

Mifeprex User Reviews

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