Intravaginal administration of RU 486 in humans and rats: inadequate absorption in humans

Vaginal mifepristone for the treatment of symptomatic uterine leiomyomata: an open-label study

OBJECTIVE

To evaluate the efficacy and safety of 3 months of vaginal mifepristone treatment on leiomyoma volume and related symptoms.

DESIGN

Prospective, open-label, two tertiary centers, phase II clinical trial.

SETTING

Two tertiary medical centers in Israel.

PATIENT(S)

Thirty-three enrolled women, ages 30-53 years, diagnosed with symptomatic uterine fibroids.

INTERVENTION(S)

Patients received 10 mg mifepristone vaginally daily for 3 months.

MAIN OUTCOME MEASURE(S)

Reduction in uterine leiomyoma volume. Improvement in symptoms related to uterine fibroids was assessed with the use of the "Uterine Fibroid Symptoms Quality of Life Questionnaire" (UFS-QoL). The number of bleeding days, safety, and tolerability were secondary measures.

RESULT(S)

Mifepristone treatment significantly reduced leiomyoma volume from 135.3 ± 22.9 cc at enrollment to 101.2 ± 22.4 cc after 3 months of treatment. The UFS-QoL Score significantly decreased from 20.7 ± 0.7 at enrollment to 14.0 ± 0.8 after 3 months of treatment. The number of bleeding days significantly decreased by 3.5 days. Endometrial biopsies showed no evidence of endometrial hyperplasia or cellular atypia. There were no major side effects during the course of the study, and treatment was well tolerated.

CONCLUSION(S)

Vaginal mifepristone may offer an effective treatment option for women with symptomatic uterine leiomyoma and can improve the patients' quality of life.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00881140.

Review of medical abortion using mifepristone in combination with a prostaglandin analogue

Induced abortion is still a major health problem in the world and the most frequently performed intervention in obstetrics and gynecology with an estimated total of 46 million worldwide each year. Medical abortion with mifepristone and prostaglandin was first introduced in 1988 and is now approved in 31 countries. This combination of drugs has recently been included in the List of Essential Medicines by the World Health Organisation. The present review summarizes the development, physiology and the development of the currently used regimens.

Mifepristone vaginally in an early medical abortion regimen: a pilot study

OBJECTIVE

This prospective observational pilot study was undertaken to assess the efficacy of mifepristone and misoprostol, both administered vaginally. The ultimate goal is to investigate alternative means of reducing the time interval between the two treatments involved. The efficacy of the early medical abortion regimen utilizing mifepristone and misoprostol is beyond doubt. The regimen usually involves administering misoprostol 36 h following oral administration of mifepristone. The interval between the two treatment components might affect a woman's choice of the medical method.

METHODS

Eighteen women undergoing abortion for nonmedical reasons were recruited.

RESULTS

Seven women required further intervention to achieve complete abortion. Median induction-to-abortion interval was 7.66 h in the 11 women with complete abortion.

CONCLUSION

The complete abortion rate of 61% in this study was lower than that with the standard medical regimen.

The pharmacokinetics of mifepristone in humans reveal insights into differential mechanisms of antiprogestin action

The pharmacokinetics of mifepristone is characterized by rapid absorption, a long half-life of 25-30 h, and high micromolar serum concentrations following ingestion of doses of >/=100 mg of the drug. The serum transport protein-alpha 1-acid glycoprotein (AAG)-regulates the serum kinetics of mifepristone in man. Binding to AAG limits the tissue availability of mifepristone, explaining its low volume of distribution and low metabolic clearance rate of 0.55 L/kg per day. In addition, the similar serum levels of mifepristone following ingestion of single doses exceeding 100 mg can be explained by saturation of the binding capacity of serum AAG. Mifepristone is extensively metabolized by demethylation and hydroxylation, the initial metabolic steps being catalyzed by the cytochrome P-450 enzyme CYP3A4. The three most proximal metabolites, namely, monodemethylated, didemethylated and hydroxylated metabolites of mifepristone, all retain considerable affinity toward human progesterone and glucocorticoid receptors. Also, the serum levels of these three metabolites are in ranges similar to those of the parent mifepristone. Thus, the combined pool of mifepristone-plus its metabolites-seems to be responsible for the biological actions of mifepristone. Recent clinical studies on pregnancy termination and emergency contraception have focused on optimization of the dose of mifepristone. In these studies it has become apparent that the doses efficient for pregnancy termination differ from those needed in emergency contraception-mifepristone is effective in emergency contraception at a dose of 10 mg, which results in linear pharmacokinetics. However, the >/=200 mg doses of mifepristone needed for optimal abortifacient effects of mifepristone result in saturation of serum AAG and thus nonlinear pharmacokinetics. In view of the pharmacokinetic data, it may be speculated that dosing of mifepristone for pregnancy termination and for emergency contraception could be reduced to approximately 100 mg and 2-5 mg, respectively. It remains to be seen whether the newly synthesized, more selective antiprogestins will prove more efficacious in the clinical arena.

Mifepristone

OBJECTIVE

To review the efficacy and safety of mifepristone (with misoprostol) for the termination of early pregnancy.

DATA SOURCES

A MEDLINE search (1966-October 2000) was conducted, and additional references listed in articles were included; unpublished data obtained from the manufacturer were used to identify data from the scientific literature. Studies evaluating mifepristone were considered for inclusion.

STUDY SELECTION

Human clinical studies in the English language were reviewed and evaluated. Clinical trials selected for detailed review were limited to those including the regimens of mifepristone and misoprostol, recently approved by the Food and Drug Administration for early pregnancy termination.

DATA SYNTHESIS

Mifepristone is an antiprogestin available for pregnancy termination in combination with a prostaglandin such as misoprostol. Mifepristone offers efficacy similar to, if not better than, other drugs used for pregnancy termination, but appears less efficacious overall than surgical termination of pregnancy. Mifepristone in combination with misoprostol commonly causes adverse effects such as abdominal pain and, less commonly, can cause serious adverse effects such as incomplete abortion; endometritis; and bleeding warranting transfusion, hospitalization, or surgery. Mifepristone is metabolized by the cytochrome P450 system. Thus, the potential for drug interactions with this agent exists, although this has not been well studied. Data are included from clinical trials evaluating the safety, tolerability, efficacy, and pharmacoeconomics of mifepristone combined with misoprostol for early pregnancy termination. Data comparing the use of these agents with surgical abortion and other drugs used for pregnancy termination are included where available.

CONCLUSIONS

Mifepristone in combination with misoprostol for the termination of early pregnancy (amenorrhea of < or = 49 d) is effective in 92-95% of women. Incomplete abortion requiring surgical abortion after the fact occurs in 3-5% of women, and pregnancy continues 1-2% of the time. Mifepristone with misoprostol treatment is not without significant risks, including hemorrhage, infection, and potential for long-term emotional consequences.

Antiprogesterone RU 486--a drug for non-surgical abortion

RU 486 is the first steroidal antiprogesterone in clinical use. It acts by binding to progesterone receptor, thus blocking the effects of progesterone at the uterine level, and provoking endometrial necrosis and shedding. RU 486 can, therefore, be used to interrupt early human pregnancy. In pregnancies of up to 7-8 weeks duration, the rate of complete abortions with RU 486 has ranged from 50% to 90%. The success rate can, however, be augmented up to 95%-100% by combining RU 486 with a low dose prostaglandin. RU 486 induced abortion has been well tolerated by women and highly acceptable to them. The bleeding starts 2-3 days after RU 486 administration lasting for 12-14 days. Possible clinical uses of RU 486 include induction of menstruation, late post-coital contraception, induction of labour after intrauterine fetal death, preoperative cervical ripening and treatment of progesterone receptor positive mammary tumours. When administered in the follicular phase of the cycle, RU 486 inhibits follicular development. In addition, the antiglucocorticoid properties of RU 486 have been used in symptomatic treatment of hypercortisolemia of Cushings disease. The pharmacokinetics of RU 486 are characterised by high micromolar serum concentrations, long half-life of 26-48 hours and substantial metabolism after oral administration. Although effective and well tolerated, RU 486 has aroused great moral controversy, which is currently hampering further testing and distribution of the drug. So far RU 486 has been accepted for termination of pregnancy in France and in the Peoples Republic of China, to be used with prostaglandins and under strict medical surveillance.