Termination of early gestation with the anti-progestin steroid RU 486: medium versus low dose

Antifertility effects of antigestogens

Since the discovery of the structure and function of steroids over 60 years ago, it has long been recognized that synthetic antagonists of the natural hormones would have potential therapeutic uses. Antagonists of mineralocorticoids, androgens and oestrogens, for example spironolactine, cyproterone, flutamide and tamoxifen, have already found a place in the management of hormone dependent conditions. In 1982, chemists at Roussel UCLAF announced that they had synthesized mifepristone (RU486) 17β-hydroxy-11(p-(dimethylamino)phenyl)-17-(1-propynyl) estra-411, 9-dien-3-one) a derivative of norethindrone which had potent antiprogestogenic as well as antiglucocorticoid activity. Although it was immediately realised that this compound would potentially have wide clinical application, its development in the last 10 years has been dominated by its abortifacient action. In the original clinical report by Herrman and colleagues it was shown that bleeding occurred when it was given to female volunteers in the second half of the menstrual cycle. In addition, complete abortion occurred in eight of 11 women who took the drug in the early weeks of pregnancy. These findings, which demonstrated that mifepristone could be used as the basis of a medical method of inducing abortion, were immediately made the focus of groups opposed to abortion on moral grounds. Experience over the last 10 years has confirmed the promise of these early studies and mifepristone, in combination with a suitable prostaglandin, is now licensed in France, UK and Sweden for use as a medical method of inducing abortion in early pregnancy.

A benefit-risk assessment of medical treatment for uterine leiomyomas

The growth of a uterine leiomyoma growth stops and regresses after the menopause suggesting that leiomyoma growth is dependent on ovarian steroids. Therefore, estrogen has received much attention as the major factor responsible for the development of uterine leiomyomas, but progesterone also plays an important role in development of this disease. Cytogenetic analyses of resected samples has revealed that about 40 to 50% of leiomyomas show karyotypically detectable chromosomal abnormalities. Gonadotrophin releasing hormone (GnRH) agonists exert their action through the suppression of endogenous gonadotrophins and gonadal steroid secretion. Significant reductions of uterine/leiomyoma volume under GnRH agonist therapy has been reported in several studies. However, the leiomyoma generally returns to its pretreatment volume within a few months after discontinuation of the GnRH agonist. To minimise the adverse effects of hypoestrogenism during GnRH agonist treatment, add back therapy can be used (estrogen-progestin, progestin alone and recently tibolone). Antiprogestins have a potential clinical utility in uterine leiomyomas. Mifepristone is a synthetic steroid with both antiprogesterone and antiglucocorticoid activities, that may have an inhibitory effect on growth of leiomyoma. Danazol is an isoxazole of 17beta-ethinyl testosterone, a synthetic steroid, which has a suppressive effect on sex hormone binding globulin concentrations, resulting in efficacy in the short-term treatment of uterine leiomyomas. Gestrinone is a tri-enic steroid with antiestrogen and antiprogesterone properties and has been shown to reduce uterine volume and stop bleeding. Growth factors play a relevant role on the pathophysiology of uterine leiomyoma and probably the inhibition of the action of growth factors on the myometrium will be the basis for future therapy. A number of agents are under investigation for treating uterine leiomyoma. Agents developed from increasing genetic knowledge of this condition could represent, in the next few years, new trends in the medical treatment of uterine leiomyomas.

Mifepristone (RU486): a review

OBJECTIVE

To review the literature concerning the mechanism of action and pharmacodynamics of mifepristone (RU486), potential new uses of RU486, and its current use not only as an abortifacient but also as therapy for endometriosis, leiomyoma, breast cancer, and meningioma.

DATA IDENTIFICATION AND SELECTION

Studies that relate to RU486 were identified through a MEDLINE search.

CONCLUSION(S)

RU486 is an 11 beta-dimethyl-amino-phenyl derivative of norethindrone with a high affinity for P and glucocorticoid receptors. The receptor binding is not followed by transcription of P-dependent genes. Mifepristone effectively blocks P receptors in the placenta, resulting in the termination of pregnancy. In addition, it has been used in the treatment of leiomyomata, endometriosis, advanced breast cancer, and meningioma. It is a powerful tool to study the molecular action of P and in the future may be used as an estrogen-free contraceptive.

Antiprogestin pharmacodynamics, pharmacokinetics, and metabolism: implications for their long-term use

Antiprogestins represent a relatively new and promising class of therapeutic agents that could have significant impact on human health and reproduction. In the present work, the pharmacodynamics, pharmacokinetics, and metabolism of mifepristone (MIF), lilopristone (LIL), and onapristone (ONA) in humans are reviewed, and characteristics bearing important clinical implications are discussed. Although MIF has gained notoriety as an "abortion pill," antiprogestins may more importantly prove effective in the treatment of endometriosis, uterine leiomyoma, meningioma, cancers of the breast and prostate, and as contraceptive agents. MIF pharmacokinetics display nonlinearities associated with saturable plasma protein (alpha 1-acid glycoprotein, AAG) binding and characterized by lack of dose dependency for parent drug plasma concentrations (for doses greater than 100 mg) and a zero-order phase of elimination. LIL and ONA pharmacokinetics are less well characterized but ONA does not appear to bind AAG and displays a much shorter t1/2 than the other agents. The three antiprogestins are substrates of cytochrome P450 (CYP) 3A4, an enzyme exceedingly important in human xenobiotic metabolism. Even more implicative of likely drug-drug interactions subsequent to their long-term administration are recent data from our laboratory indicating that they inactivate CYP3A4 in a cofactor- and time-dependent manner, suggesting that complexation and induction of the enzyme may occur in vivo via protein stabilization. Moreover, it has been demonstrated that MIF increases CYP3A4 mRNA levels in human hepatocytes in primary culture, indicative of message stabilization and/or transcriptional activation of CYP3A4 expression. Finally, MIF has also been shown to inhibit P-glycoprotein function. Whether LIL and ONA share these latter two characteristics with MIF has not yet been determined but they illustrate properties that, in addition to diminished antiglucocorticoid activities and altered pharmacokinetic characteristics, warrant consideration during the development of these and never antiprogestational agents.

Determination of RU486 (mifepristone) in blood by radioreceptorassay; a pharmacokinetic study

A human progesterone receptor assay has been developed for the measurement of the biologically active molecular fraction of RU486 (RU486 binding equivalent) for studying its pharmacokinetic properties. Thirty-nine healthy pregnant volunteers with amenorrhoea of 49 days or less receiving a single oral dose of 200 mg, 400 mg or 600 mg RU486 orally in a single dose were involved in this study. Blood samples were collected within 48 hours for the analysis. It was found that the pharmacokinetics of the RU486 binding equivalent followed an open two-compartment model. The dose was rapidly absorbed and peak serum concentrations were measured within 1-2 hours after ingestion of the drug. The distribution was also rapid, but the elimination was slow, the elimination half-life ranging between 83 and 90 hours. Significant differences were found between the peak plasma values for the 200 mg and 600 mg doses (p < 0.05) and between the AUCs for the 200 mg and 600 mg doses (p < 0.01) and the 400 mg and 600 mg doses (p < 0.05). It can be concluded that this newly developed radioreceptor assay satisfies the requirements of radioligand binding techniques and can be used to determine the serum levels of RU486 and its metabolites, which are able to bind to human myometrial progesterone receptors. The pharmacokinetics for the RU486 binding equivalent is similar to that for RU486, with the exception of very slow elimination, which may originate from the measurement of the biologically active metabolites together with the parent compound.

The use of misoprostol for termination of early pregnancy

Misoprostol is a prostaglandin analogue which has uterotonic properties. Administered vaginally, it is an effective agent for induction of second trimester abortions. This study was undertaken to determine if the vaginal administration of misoprostol is effective for inducing first trimester abortions. Fifty-eight women with pregnancies less than 10 weeks gestation who desired pregnancy termination received varying dosages of vaginal misoprostol, either alone or in combination with laminaria or tamoxifen. The overall success rate for a complete abortion was 61%. The use of laminaria or tamoxifen did not affect success rates. Abortions occurred within 24 hours of administration of misoprostol. Side effects were minimal. There were no significant differences in any of the following between those who had a successful abortion and those who did not: gravidity, parity, prior elective abortion, age, gestational age of the pregnancy, and level of human chorionic gonadotropin. Although not as successful as other combination regimens, misoprostol alone is readily available, easy to administer, and without major side effects. The use of this agent could eliminate the need for about two-thirds of surgical abortions in the first 10 weeks of gestation.

Termination of early pregnancy in the rat, rabbit, and hamster with RU 486 and anordrin

The effectiveness of oral RU 486 and anordrin given alone and in combination for terminating early pregnancy was tested in the rat, rabbit, and hamster. In the rat and rabbit, the combination of RU 486 and anordrin is more effective in terminating pregnancy than either of the two compounds used alone. A non-effective dose of RU 486 combined with a non-effective or a sub-effective dose of anordrin, or a low effective dose of RU 486 in combination with a non-effective dose of anordrin, exerted additive or synergistic effects resulting in resorption of embryos and termination of pregnancy in rats and rabbits. The serum progesterone as well as estradiol concentrations were significantly suppressed by these combinations when pregnancy was terminated. In the hamster, however, RU 486 was not effective in interrupting early pregnancy, even at a 4-fold higher dose than was effective in the rat, due to the fact that RU 486 does not bind to the progestin receptor in this species. Unexpectedly, there were also no effects of anordrin on pregnancy termination in the hamster even at high doses. It is concluded that in rat and rabbit, the synergistic action between RU 486 and anordrin not only greatly enhances efficacy in terminating pregnancy but also reduces substantially the doses required to produce this effect.

Dose-response relationships of RU 486

Clinical experience has indicated that the effects of RU 486 can be divided into dose-dependent and dose-independent effects. Examples of the dose-dependent effects include the antiglucocorticoid effects of RU 486, whereas pregnancy termination or dilatation of the cervix can be considered dose-independent with the various regimens tested so far. Following oral intake in man, the serum levels of RU 486 are in the micromolar range, and the half-life is approximately 30 hours. The concentrations of RU 486 in myometrial tissue are approximately one-third of those measured in serum. However, due to saturation of alpha 1-acid glycoprotein (AAG), the serum binding protein for RU 486, the serum levels remain similar within the dose range of 100-800 mg of RU 486. The unbound RU 486 is metabolized by two-step demethylation or by hydroxylation. The demethylated and hydroxylated metabolites of RU 486 retain considerable affinities of 9-21% towards the human progesterone receptor, and 45-61% towards the human glucocorticoid receptor (RU 486 = 100%), suggesting a biological role for the metabolites. Rat serum lacks a specific binding protein for RU 486. Even though the levels of RU 486 in rat adipose tissue are 40 times as high as those seen in serum, the concentrations of RU 486 in rat brain are only 28% of the serum levels. This indicates that diffusion of RU 486 into the central nervous system is restricted by the blood-brain barrier. Hence, the dose-dependency of certain centrally mediated effects of RU 486 might be explained by the limited diffusion of RU 486 into hypothalamic/hypophyseal sites, which seem to be reached only after ingestion of high doses of RU 486. However, the peripheral effects of RU 486, such as termination of pregnancy, are mediated via steroid receptors in target tissues. This suggests that similar biological effects can be attained at considerably lower doses than the ones currently in use.

Cervical softening with mifepristone (RU 486) after pretreatment with naproxen. A double-blind randomized study

Pretreatment with the progesterone antagonist mifepristone reduces the stiffness and facilitates mechanical dilatation of the uterine cervix. We studied the influence of the cyclo-oxygenase inhibitor naproxen on the softening effect of mifepristone on the cervix in thirty nulliparae. The patients were randomly allocated to receive 500 mg naproxen (group A) or placebo (group B) orally 60, 48, 36, 24 and 12 hours prior to vacuum aspiration. All patients received 100 mg mifepristone 48 and 36 hours before surgery. We found that the cervical softening effect of mifepristone was not antagonized by naproxen. The study indicates that the effect of mifepristone on the early pregnant cervix is not mediated through an increased production of prostaglandins.

Mifepristone (RU486) alone or in combination with a prostaglandin analogue for termination of early pregnancy: a review

The availability of a medical mode of termination of early pregnancy by the administration of RU486, an antiprogesterone alone, or in combination with one of the PG analogues significantly reduces the maternal morbidity and mortality associated with the classical surgical abortion. RU486 given alone in early pregnancy induces complete abortion in 60% to 85% of cases, and when combined with prostaglandin analogues, gemeprost or sulprostone, reaches a success rate of 95% to 99%. RU486 may also be of potential value in the medical treatment of ectopic pregnancy. Its use as a postcoital contraception is suggested, but further research is required to determine whether RU486 can be used on a once-a-month basis for contraception.

Oral administration of RU 486 and 9-methylene PGE2 for termination of early pregnancy

It has been shown that the antiprogestin RU 486 increases the sensitivity of the early pregnant human uterus to the stimulatory action of prostaglandin E analogues administered vaginally or intramuscularly. To examine if RU 486 also increases uterine sensitivity to a PGE analogue given orally, two investigative approaches were used in the present study: 1) direct registration of uterine contractions before and after administration of 9-methylene PGE2 in untreated and RU-486-treated early pregnant women; and 2) an efficacy trial involving treatment of pregnant women (amenorrhea of 49 days or less) with 25 mg RU 486 twice daily for three or four days followed by 2.5, 5.0 or 10 mg 9-methylene PGE2, or 600 mg RU486 followed by 10 mg 9-methylene PGE2 administered on day 3 and 4. The results showed that oral 9-methylene PGE2 had a clear stimulatory effect on uterine contractility which was further increased by pretreatment with RU 486. Following 2.5, 5.0 or 10.0 mg 9-methylene PGE2, the frequency of complete abortion was the same, or approximately 80%. The success rate is higher than that generally reported for RU 486 treatment alone. If 600 mg RU 486 was complemented with 10 mg 9-methylene PGE2 administered on both days 3 and 4, the frequency of complete abortion increased to 95%. Side effects were of a mild nature and generally occurred following administration of 9-methylene PGE2. The results of the present study indicate that a combined treatment based on oral administration of both the antiprogestin and the prostaglandin analogue can be developed into a highly effective and simple method to terminate early pregnancy.

Predictors of failed attempted abortion with the antiprogestin mifepristone (RU 486)

The experience of 271 patients who received mifepristone (RU 486) in experimental protocols from July 1984 to January 1989 was analyzed by logistic regression methods. The regimen used was the strongest predictor of failure, followed by Quetelet's index and initial beta-human chorionic gonadotropin level. The relative risk of failure was 2.3 times with 7-day regimens and 6.3 times with the other regimens that obtained with regimens of 600 mg given once or twice. The relative risk of failure increased with increasing Quetelet's index; women in the top quartile were 2.9 times more likely to fail to abort than were women in the bottom quartile. The risk of failure increased with increasing initial beta-human chorionic gonadotropin level; those with an initial level greater than 19,800 mIU/ml were 2.8 times more likely to fail to abort than were women with an initial value less than or equal to 6350 mIU/ml. Body mass appears to influence the likelihood of abortion with mifepristone.

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.

The use of the antiprogestin RU486 (mifepristone) as an abortifacient in early pregnancy--clinical and pathological findings; predictive factors for efficacy

RU486, a potent antiprogesterone steroid was administered to 124 women requesting therapeutic abortion. All were less than 49 days from their last menstrual period. Ten of these subjects (Group I) received high doses of RU486 in a decremental dose regimen (400, 300, 200 and 100 mg/day) over 4 successive days and 14 received 50 mg/day for 7 days (Group II). A further 50 subjects (Group III) received 100 mg/day for seven days and the remaining 50 subjects (Group IV) received 450 mg in a single dose. In the first three groups, half the daily dose was given in the morning and the remainder in the evening. Blood was collected before, and on Days 4 and 7 and then once a week after commencing therapy until disappearance of circulating beta HCG. In addition to beta HCG, estradiol-17 beta (E2), progesterone (P), cortisol, and various metabolic and hematological parameters were measured. Plasma RU486 concentrations were also assayed in Group II, III and IV subjects on Day 7 of therapy and in some cases on Days 14 and 21. Ultrasonography was performed in all cases on Day 1 and on Day 14. All the patients bled within five days following RU486 administration, for 1 to 21 days. A complete abortion occurred in 60% in Group I, 50% in Group II, 86% in Group III, and 80% in Group IV. The difference between the last two groups and the first two was significant at p less than 0.01. The non-responders were submitted to a uterine vacuum aspiration. A stepwise discriminant analysis was performed and indicated that the best predictors of the outcome of therapy were beta HCG values and the gestational sac diameter. With these criteria, the prediction was accurate in 86.4% of the cases. The best results were obtained in the cases where the ultrasonic measurement of gestational sac was under 10 mm in diameter and the initial beta HCG values under 15,000 mIU/ml. Among the observed side effects were moderate pelvic cramps (20.9%), nausea (27%), fainting (4.8%); 61.3% of the women complained of fatigue. Heavy bleeding occurred in 15.3% of the women but only one of them required blood transfusion. In the patients with complete abortion, beta HCG values decreased to below 500 mIU/ml by Day 14 (but in 11 cases values fell below 2,000 mIU/ml only by Day 21). Plasma estradiol and progesterone also fell. Cortisol levels increased during therapy especially in subjects of Group I, but returned to basal values after termination of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacokinetic study of orally administered RU 486 in non-pregnant women

A method based on HPLC was devised for the estimation of RU 486 in blood and utilised to study the pharmacokinetics of a single dose of 50 mg RU 486 administered orally to 12 women on day 7 of the cycle. The dose was rapidly absorbed with peak plasma concentration between 1 and 2 hours. Distribution was also rapid (mean t1/2 alpha: 1.4h), whereas elimination was slow (mean t1/2 beta: 28.3 h). RU 486 was still detectable in some women at 72 h after administration. The plasma concentrations fitted the equation for a two-compartment open model from which the pharmacokinetic parameters were calculated. The mean total plasma clearance was 3.0 l/h, and the comparison of our data with those published studies suggests that the pharmacokinetics of RU 486 in Chinese women are similar to those of other populations.

Contragestion and other clinical applications of RU 486, an antiprogesterone at the receptor

RU 486, a steroid with high affinity for the progesterone receptor, is the first available active antiprogesterone. It has been used successfully as a medical alternative for early pregnancy interruption, and it also has other potential applications in medicine and for biochemical and pathophysiological endocrine research.

Binding characteristics of progesterone and antiprogestin ZK 98.299 in human endometrial and myometrial cytosol

The binding of ZK 98.299, a synthetic progesterone antagonist, with human endometrium and myometrium cytosol was studied and compared with that of progesterone. Progesterone showed specific saturable binding to its receptors in both endometrium and myometrium. ZK 98.299 and progesterone were mutually competitive for binding to progesterone receptors; however, the relative binding affinity of ZK 98.299 was 16% that of progesterone. ZK 98.299 exchanged the progesterone-labelled receptor sites. [3H]ZK 98.299 showed specific binding which was linearly related to the cytosol protein concentration. The binding was not saturable at 15 nM of ligand. The binding capacity and binding affinity of ZK 98.299 receptor was less than that of progesterone. Progesterone also partially displaced the binding of [3H]ZK 98.299. This study suggest that ZK 98.299 and progesterone both bind to the same protein. However, whether ZK 98.299 binds to progesterone receptors alone or even to other functionally related sites is not known. It appears that ZK 98.299 when present in higher concentration than progesterone would be an effective receptor ligand.

Retained pregnancy complicating donor ovum transfer

Retained pregnancy is an uncommon complication of females participating in uterine lavage for purposes of ovum donation. Reported are two subjects experiencing this complication. Unlike other ovum donors, uterine retroflexion was present in both women. This anatomic configuration was likely responsible for the retained pregnancies and such women are best excluded from participating in this method of embryo donation.

The use of prostaglandins and antiprogestins for pregnancy termination

Although vacuum aspiration could be regarded as a simple procedure, complications do occur and attempts have been made to develop non-surgical procedures for termination of pregnancy during the first 3-4 weeks following the first missed menstrual period. A variety of prostaglandin (PG) analogs have been developed which are equally effective as vacuum aspiration to induce abortion during early pregnancy. However, the widespread acceptance of PG treatment is limited by a relatively high incidence of gastrointestinal side effects and uterine pain. Treatment with presently available antiprogestins alone is not sufficiently effective to compete with vacuum aspiration. However, administration of these compounds induces uterine contractions and increases the sensitivity of the myometrium to prostaglandin. These effects allow the development of sequential treatment with RU 486 and a low dose of PG analogs administered intramuscularly or vaginally which is highly effective and is seemingly associated with a lower frequency of side effects than if PG analogs are used alone. It can be concluded that this medical abortion method has the capacity to compete with vacuum aspiration for termination of early pregnancy. Randomized studies comparing the two procedures are, however, needed to confirm this statement.

Pharmacokinetics of the antiprogesterone RU 486 in women during multiple dose administration

Serum levels of RU 486 were measured by high performance liquid chromatography (HPLC) following oral intake of 12.5, 25, 50 and 100 mg twice daily (b.i.d.) for 4 days, 50 mg b.i.d. for 7 days, as well as a single dose of 200 mg of RU 486. The pharmacokinetics of RU 486 were not linear: when the daily dose of RU 486 was 100 mg or more, the serum levels were similar. The pharmacokinetic behaviour of RU 486 during the treatment period was similar between the study subjects, whereas the elimination phase pharmacokinetics showed wide individual variation. Also the mean elimination phase half-lifes (t 12) of RU 486 varied from 25.5 to 47.8 h in the groups of different regimen, yet the variation between different groups was not statistically significant. The areas under the concentration curves (AUC) were calculated. In the multiple dose study (mds) the AUC0----12h:s decreased when the administered dose of RU 486 was increased. The AUC0----12h seen after administration of 100 mg b.i.d. x 4d. (mean +/- SEM = 0.43 +/- 0.04 mumol/l x h/mg) was significantly (P less than 0.05) lower than the AUC0----12h:s obtained with administration of 12.5 mg b.i.d. x 4d. (1.49 +/- 0.37 mumol/l x h/mg), 25 mg b.i.d. x 4d. (1.09 +/- 0.15 mumol/l x h/mg), and 50 mg b.i.d. x 7d. (0.72 +/- 0.11 mumol/l x h/mg). The AUC0----infinity obtained by administration of a single dose of 200 mg of RU 486 (sds) was 0.67 +/- 0.21 mumol/l x h/mg. It is concluded that if multiple dose administration of RU 486 is preferred, daily administration of relatively small doses of RU 486 over several days seem to be advantageous.

Prostaglandins and antiprogestins

There is considerable interest in the development of a non-surgical method to terminate early pregnancy. During the three weeks immediately following the first missed menstrual period, several prostaglandin (PG) analogs such as sulprostone, gemeprost and 9-methylene PGE2 have been used to terminate the pregnancy. Prostaglandins, however, at the doses required to induce disruption of the conceptus cause gastrointestinal side effects and uterine pain which are more severe than those subsequent to vacuum aspiration. Treatment with the antiprogestin, mifepristone counteracts the effects of progesterone in pregnancy and thus prevents maintenance of the pregnancy. Mifepristone administered alone causes termination of the pregnancy in most, but not all, cases. In addition to removing the influence of progesterone, mifepristrone also induces regular uterine contractions and significantly increased the sensitivity of the uterus to PG analogs. Mifepristone (50 mg/day) followed by an intramuscular injection of a low dose, (0.25 mg), of sulprostone (approximately 1/6 of the dose of prostaglandin necessary to induce abortion if used alone) was highly effective in terminating early pregnancy, causing complete abortion in 94% of cases. Gastrointestinal side effects were rare and uterine pain significantly less common than if PG analogs were used alone. Subsequently the combination of mifepristone and vaginal administration of gemeprost (0.5-1.0 mg) has been shown to be equally effective Ideally, the PG analog would be administered orally rather than by injection or vaginal administration. Preliminary data indicate that 9-methylene PGE2 but not PEG2 may be suitable for this purpose in combination with mifepristone.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-progesterones for the interruption of pregnancy

Therapeutic abortion can be performed effectively and safely by vacuum aspiration of the uterus up to 12 weeks of amenorrhoea. Although the operative procedure could be regarded as simple, complications do occur and attempts have been made to develop non-surgical means of terminating pregnancy in the first 3-4 weeks following the first missed menstrual period. A variety of PG analogues have been developed which induce abortion in over 90% of women when given by vaginal pessary or intramuscular injections (see Bygdeman, 1984). In a large multicentre study (WHO, 1987) 0.5 mg sulprostone, administered three times with 3 h intervals, was recently found to be equally as effective as vacuum aspiration for termination of early pregnancy. The frequencies of complete abortion were 91 and 94%, respectively. However, the widespread acceptance of PG treatment is limited by a relatively high incidence of gastrointestinal side-effects and uterine pain. Treatment with antiprogesterones, both mifepristone and epostane, effectively induces abortion during early pregnancy, but the frequency of complete abortion is too low to be clinically acceptable. It remains to be demonstrated if other antiprogesterones such as ZK 98.734 and ZK 98.299, currently under development, may change this conclusion. Administration of mifepristone induces uterine contractions and increases the sensitivity of the myometrium to prostaglandins. These effects allowed the development of sequential treatment with a low dose of mifepristone and PG analogues administered vaginally or intramuscularly. The combined therapy has been shown to be highly effective (frequency of complete abortion between 95 and 100%) and is seemingly associated with a lower frequency of side-effects than if PG analogues are used alone. Whether this medical abortion method will be a realistic alternative to vacuum aspiration during the first 8 weeks of pregnancy depends on the outcome of further clinical trials, including randomized studies comparing the two procedures. It has been shown that mifepristone crosses the placenta (Frydman et al, 1985). An important factor which needs to be verified in future studies is therefore the possible embryotoxicity of this type of compound. The risk that pregnancy continues in spite of treatment can never be excluded.(ABSTRACT TRUNCATED AT 400 WORDS)

Future directions: anti-hormones in reproductive medicine

Anti-hormones are important in reproductive medicine because they are useful tools that teach us about the normal physiological actions of hormones. They also provide effective therapies to control or treat a variety of pathogenic processes. We expect that the future repertoire of anti-hormones will include the paracrine and autocrine regulators of specific cell functions, in addition to the endocrine systems described here. The availability of recombinant DNA expression systems for an ever larger portion of the human genome will surely accelerate the development of novel anti-hormones.

Early abortion with a single dose of the antiprogestin RU-486

RU-486 is a synthetic progesterone antagonist that is abortifacient in early pregnancy. This trial evaluated the effectiveness and safety of a single 600 mg oral dose given to 50 healthy women less than or equal to 49 days from their last menstrual period. Efficacy was inversely related to the initial beta-subunit of human chorionic gonadotropin level, ranging from 100% at less than 5000 mIU/ml to 81% at greater than 20,000 mIU/ml (p less than 0.05). Uterine bleeding was the most serious side effect. However, the mean change in the hemoglobin value 14 days after treatment was -0.4 gm/dl, and no patient required blood transfusion. This regimen appears to be simple, effective, and safe.

Effects of the antiprogesterone RU 486 in normal women. I. Single-dose administration in the midluteal phase

The response to a single oral dose of the antiprogesterone RU 486 was studied in the midluteal phase in 26 normal women. Each subject received a dose between 50 and 800 mg RU 486 on days 6 to 8 after the luteinizing hormone surge and blood samples were taken over the following 48 hours. Another group of five patients received a single oral dose of 200 mg RU 486 and blood sampling was extended for 14 days. Menses were induced in all women but one within 3 days after RU 486 administration. Two distinct patient populations emerged. In nine of the subjects, there was a single bleeding episode and the treatment cycle was significantly shorter (p less than 0.05) than the following cycle. In 16 of these 25 patients a second bleeding episode occurred 19.0 +/- 0.8 days after the luteinizing hormone surge. The total treatment cycle was significantly prolonged (p less than 0.05) when compared with the following cycle. In the group with a single bleeding episode, there was a significant decline in follicle-stimulating hormone, estradiol, and progesterone over the 48-hour sampling period, but there was no change in these values in the group with two bleeding episodes. These two groups could not be separated on the basis of RU 486 dose or serum levels. After the four higher doses, there was a dose-dependent rise in serum prolactin. There were no alterations in mean cortisol values with the three lower doses, but there was a significant increase at 24 and 48 hours after the higher doses. Serum levels of RU 486 were maximal between 1 and 4 hours and the half-life of serum RU 486 was determined to be 24 hours.