Development of a high-performance liquid chromatographic method for the determination of mifepristone in human plasma using norethisterone as an internal standard: application to pharmacokinetic study

OBJECTIVE

The objective of this study was to develop a simple, sensitive, stable and validated HPLC method for the determination of mifepristone levels in human plasma.

METHODS

Solid-phase extraction cartridges were used to extract plasma samples. Separation was carried out on a C(18) column maintained at 20 degrees C with acetonitrile-water (80:20, v/v) as mobile phase at a flow rate of 0.6 mL/min. Norethisterone was employed as the internal standard. Dual wavelength mode was used, with mifepristone monitored at UV 302 nm and norethisterone at 240 nm.

RESULTS

The calibration curve was linear in the concentration range of 5-10000 ng/mL, with linear correlation coefficient r being 0.9999. The limit of detection for the assay was 3 ng/mL. The inter-day accuracy ranged from 92.4% to 98.4% and precision 3.6% to 11.4%. The intra-day accuracy ranged from 92.1% to 100.6% and precision 4.7% to 12.2%. The absolute recovery was 91.7-100.1%. Plasma samples were stable for at least 1 month if stored at -20 degrees C. This validated HPLC method was successfully applied to pharmacokinetic study of mifepristone in human plasma samples collected from volunteers after oral administration of 10 mg mifepristone.

CONCLUSION

The simple, accurate and stable method allows the sensitive determination of mifepristone in human plasma at the nanogram level. It could be applied to assess the plasma level of mifepristone in women up to 5 days after oral administration of 10 mg mifepristone.

Simultaneous determination of rivanol and mifepristone in human plasma by a HPLC-UV method with solid-phase extraction

A HPLC method with UV detection was developed and validated for the simultaneous determination of rivanol and mifepristone in human plasma. Norethisterone was used as the internal standard. Separation was performed by a C18 reversed-phase column maintained at 20 degrees C. The mobile phase was a mixture of methanol-acetonitrile-0.05% sodium dodecylsulfonate in a 0.05 M phosphate buffer with the pH adjusted to 3.0 (30:30:40, v/v/v) at a flow rate of 0.8 ml/min. Dual wavelength mode was used, with mifepristone monitored at UV 302 nm, while rivanol and norethisterone at 272 nm. A reliable biological sample pre-treatment procedure by means of solid-phase extraction was used, which allowed to obtain good extraction efficiency (>93%) for both of the analytes and the internal standard. The calibration curves were both linear with the correlation coefficient r equal to 0.9999. For rivanol, the assay gave CV% values for precision always lower than 7.8% and mean accuracy values higher than 95.3%. As to mifepristone, precision was always lower than 10.1% and mean accuracy values were higher than 93.8%. The limit of detection for the assay of rivanol and mifepristone was 1.1 and 3 ng/ml, respectively. The method is simple, sensitive and accurate, and allow for simultaneous determination of nanogram levels of rivanol and mifepristone in human plasma. It could be applied to assess the plasma level of rivanol and mifepristone in women undergoing polypharmacy with the two drugs.

Intraperitoneal delivery of exogenous corticosterone via osmotic pump in a passerine bird

Selecting the most reliable method to deliver exogenous steroids remains a problem for researchers, particularly when designing experiments on small birds. We used intraperitoneal (IP) osmotic pumps to deliver exogenous corticosterone (CORT) and RU486 in captive White-throated Sparrows. Males received implants containing either a low (LD) or moderate dose (MD) of CORT, RU486 (RU), or polyethylene glycol vehicle only (V). This method provided sustained elevations in baseline CORT in both LD and MD males compared to V males, with higher CORT levels induced in MD males. Slight increases in post-implant CORT resulted in V males, but not in RU males. We observed no significant change in the condition of V males in terms of body mass, furcular fat score or food intake rates, although locomotor activity declined slightly after implantation. Taken together, our results suggest that IP pumps had little impact on the overall health of the birds. CORT levels were maintained within natural ranges for this species, suggesting that our results are biologically relevant and useful for future endocrine studies with small birds.

An HPLC method for the determination of ng mifepristone in human plasma

An HPLC method was developed and validated for the determination of mifepristone in human plasma. C(18) solid-phase extraction cartridges were used to extract plasma samples. Separation was by C(18) column; mobile phase, methanol-acetonitrile-water (50:25:25, v/v/v); flow rate, 0.8 ml/min; UV detection at 302 nm. The calibration curve was linear in the concentration range of 10 ng/ml to 20 microg/ml (r=0.9991). Within- and between-day variability were acceptable. The limit of detection for the assay was 6 ng/ml. Plasma samples were stable for at least 7 days in the state of plasma or residue treated at -20 degrees C. The method was simple, sensitive and accurate, and allowed to determine ng mifepristone in human plasma. It could be applied to assess the plasma level of mifepristone in women receiving low oral doses of mifepristone.

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.

[Pharmacokinetics of mifepristone and kinetics of chorionic gonadotropin beta-subunit (beta-HCG) and progesterone in plasma of pregnant women during pharmacological interruption of early pregnancy]

Reliable correlations between the parameters of mifepriston pharmacokinetics describing the rate of drug elimination from the blood plasma and the levels of beta-human chorionic gonadotropin (beta-HCG) and progesterone reflecting the state of gestation in females have been established fore the first time. According to these relationships, the half elimination time, the mean retention time, and the plasma clearance of mifepriston can be considered as predictors of the clinical efficacy of this drug for the early pregnancy interruption.

Glucocorticoids act in the dorsal hindbrain to increase arterial pressure

Glucocorticoid receptors (GRs) are present at a high density in the nucleus of the solitary tract (NTS), an area of the dorsal hindbrain (DHB) that is critical for blood pressure regulation. However, whether these receptors play any role in the regulation of blood pressure is unknown. We tested the hypothesis that glucocorticoids act in the DHB to increase arterial pressure using two experimental strategies. In one approach, we implanted pellets of corticosterone (Cort) or sham pellets onto the DHB over the NTS. Compared with rats with sham pellets, rats with DHB Cort pellets had an increased ( P < 0.05) mean arterial pressure (111 ± 2 vs. 104 ± 1 mmHg) and heart rate (355 ± 9 vs. 326 ± 5 beats/min) after 4 days. In the second approach, we implanted subcutaneous Cort pellets to increase the systemic Cort concentration and then subsequently implanted pellets of the GR antagonist mifepristone (Mif; previously RU-38486) or sham pellets onto the DHB. Two days of DHB Mif treatment reduced ( P < 0.05) mean arterial pressure in those rats with elevated plasma Cort levels (118 ± 2 vs. 108 ± 1 mmHg for sham vs. Mif DHB pellets). Cort and Mif pellets placed on the dura had no effects on arterial pressure or heart rate, ruling out systemic cardiovascular effects of the steroids. DHB Cort treatment had no effects on plasma Cort concentration or adrenal weight, indicating that the contents of the DHB Cort pellet did not diffuse into the systemic circulation or into the forebrain areas that regulate plasma Cort concentration in concentrations sufficient to produce physiological effects. Immunohistochemistry for the occupied GRs demonstrated that the Cort and Mif from the DHB pellets were delivered to the DHB with minimal diffusion to the ventral hindbrain or forebrain. We conclude that glucocorticoids act in the DHB to increase arterial pressure.

Determination of mifepristone levels in wild canid serum using liquid chromatography

An HPLC method was developed to determine levels of mifepristone, in coyote (Canis latrans) serum where mifepristone will be used as an oral contragestive agent for nonlethal predator control. Serum samples were extracted using C(18) solid-phase extraction cartridges. A synthetic analog of mifepristone, RTI-3021-003, was used as the internal standard. Separation of the compounds was achieved by using a C(18) (150 x 4.6 mm) column. The mobile phase was 55% acetonitrile in water running at 1.0 ml/min with UV detection at 305 nm. The assay was linear in the range of 10 to 1000 ng/ml. Inter-day accuracies for 10, 200 and 1000 ng/ml were 95.9, 99.4 and 104.7%, respectively. Inter-day precisions measured by RSD were 19.8, 9.7 and 4.5%. Intra-day accuracies were 117, 106.9 and 99.4% for 10, 200 and 1000 ng/ml, respectively. Intra-day RSDs were 19.7, 3.7 and 9.3%, respectively. A simple, sensitive and validated HPLC analytical method was developed to quantitate mifepristone in canine serum.

Glucocorticoid involvement in suppression of NK activity following surgery in rats

We studied plasma factors mediating suppression of NK activity (NKA) following surgery. Plasma from operated rats suppressed NKA of splenocytes, leukocytes, and purified natural killer (NK) cells, and charcoal stripping nullified suppression. The glucocorticoid antagonist mifepristone prevented suppression, whereas blockers of reactive oxygen metabolites, opioids, catecholamines, prostaglandin-E2, and histamine did not. NKA dropped as corticosterone levels peaked postoperatively, and administration of relevant doses of corticosterone suppressed NKA. Inhibition of glucocorticoid synthesis prevented plasma from suppressing NKA but merely attenuated NKA suppression in operated rats. Thus, postoperative concentrations of corticosterone can directly suppress NKA but additional factors probably act in vivo.

Transactivation assay for determination of glucocorticoid bioactivity in human serum

We have developed a mammalian cell (COS-1) bioassay, which measures glucocorticoid bioactivity (GBA) directly from a small amount of human serum. The assay is based on the expression of human glucocorticoid receptor (GR) together with a coactivator protein and reporter plasmid containing GR response elements upstream of the luciferase gene. Ten microliters of human serum, in duplicate, are added directly to the cell culture medium, and GBA is derived from reporter gene activity. The assay differentiates between biopotencies of synthetic steroids, and importantly, mifepristone (RU486) is able to block glucocorticoid-induced response. The assay is sensitive (<15.6 nM cortisol in fetal calf serum) and precise, with the within- and between-assay coefficients of variation less than 8% and 10%, respectively. We measured serum GBA (bioassay) and cortisol (RIA) levels in 34 asthmatic children (age range, 5.7-14.2 yr) at baseline and after treatment with either inhaled budesonide (800 microg/d, n = 14), fluticasone propionate (500 microg/d, n = 14), or cromones (control group, n = 6). Pretreatment serum GBA and cortisol levels correlated strongly (r = 0.90, P < 0.0001, n = 34). Two months of treatment with inhaled budesonide resulted in excess GBA in circulation, which was not attributable to endogenous cortisol (P < 0.001). In the fluticasone propionate group, the presence of serum excess GBA was at the borderline of statistical significance (P < 0.08) after 2 months of inhalation therapy, and no excess GBA was detected in the cromone group. In conclusion, our bioassay enables measurement of mammalian cell response to bioactive glucocorticoids in circulation and provides a novel means to investigate patients receiving drugs acting through the GR.

Circulating concentrations of the antiprogestins CDB-2914 and mifepristone in the female rhesus monkey following various routes of administration

The overall aim of these studies was to investigate the oral and i.m. bioavailability of CDB-2914 in intact female rhesus monkeys, and to compare the serum concentrations of CDB-2914 with that of mifepristone following oral administration. In the first study, a 50 mg bolus of CDB-2914 per monkey was administered intravenously, orally or intramuscularly. The area under the serum concentration-time curve for 72 h (AUC(0-72)) following i.v. injection was 18 320 +/- 2718 ng/ml*h, and that for oral administration was 10 464 +/- 3248 ng/ml*h. Thus, the oral bioavailability of CDB-2914 equivalents was 56%. The AUC(0-168 h) following i.m. injection was 11 226 +/- 1130 ng/ml*h. Therefore, the i.m. bioavailability of CDB-2914 equivalents was 62%. In the second study, the serum concentrations of CDB-2914 and mifepristone equivalents were compared following an oral bolus dose in two different formulations. When administered at 5 mg/kg in aqueous suspending vehicle (ASV), the mean peak serum concentration (C(max)) of CDB-2914 equivalents (192 +/- 64 ng/ml) occurred at 5 +/- 1 h, whereas the C(max) of mifepristone equivalents (82 +/- 25 ng/ml) occurred at 3 +/- 1 h. Following administration in gelatin capsules (35 mg/monkey), the C(max) of CDB-2914 equivalents (129 +/- 24 ng/ml) occurred at 5 +/- 1 h, while the C(max) of mifepristone equivalents (31 +/- 8 ng/ml) occurred at 3 +/- 1 h. The serum concentration (AUC(0-120 h)) of CDB-2914 equivalents was 4.7- or 5. 3-fold greater than that of mifepristone equivalents when administered orally in ASV or gelatin capsules respectively. The serum protein binding characteristics of CDB-2914 were also studied. CDB-2914 bound to human alpha(1)-acid glycoprotein (AAG), but not with as high an affinity as mifepristone. In contrast, neither CDB-2914 nor mifepristone bound with high affinity to AAG, corticosteroid binding globulin or sex hormone binding globulin in monkey serum. Collectively, these results indicated that CDB-2914 was more efficiently absorbed than mifepristone following oral administration to female rhesus monkeys.

Induction of labor with mifepristone--a randomized, double-blind study versus placebo

OBJECTIVE

To evaluate the efficacy of mifepristone in inducing labor in women with an unripe cervix, its effect on the cervix and on the status of the newborn.

METHODS

In a prospective double-blind study, 36 post-term pregnant women with a Bishop score of 5 or less received either 400 mg mifepristone (n=24) or placebo (n=12). If, 48 hours after the treatment was started, labor had not begun or the Bishop score was 5 or less, the women were given 0.5 mg prostaglandin E2 intracervically, a treatment which was repeated 12 hours later, if necessary.

RESULTS

During the first 48 hours following treatment, 19 (79.2%) of the women treated with mifepristone and two of the women (16.7%) treated with placebo went into labor. In addition, one and three women, respectively, had a ripe cervix at the end of the 48h period. The overall success rate was thus 83.3% for mifepristone and 41.7% for placebo (p=0.008; OR 14.8; 95% CI 2.1-107.6). The median time from the start of treatment to delivery was also shorter (mifepristone 36h23' and placebo 53h17'). Treatment with intracervical PGE2 was needed more often after the placebo. The duration of labor, however, tended to be shorter after placebo than after mifepristone in the women who delivered vaginally. The frequencies of instrumental delivery were similar in both treatment groups. The median Apgar score was slightly lower at 1 minute (p<0.05) following mifepristone treatment, but did not differ at 5 and 10 minutes. There was no difference between the two treatment groups in the umbilical pH at delivery.

CONCLUSION

The results of the present study show that mifepristone is a simple and effective treatment for inducing labor in post-term women with an unripe cervix.

Cervical ripening with mifepristone before labor induction: a randomized study

OBJECTIVE

To determine the efficacy and safety of mifepristone for cervical ripening in post-term pregnancies.

METHODS

Women with post-term pregnancies and Bishop scores less than 6 were assigned randomly to mifepristone (41 patients) or placebo (42 patients). Mifepristone was given orally in a dose of 400 mg. Efficacy was assessed by change in the Bishop score within 48 hours after treatment; a score of 6 or greater was considered a "strict" success. An "extended" success rate was defined, including all patients with scores of at least 6 or those who delivered within 48 hours of treatment. Antenatal safety was assessed by fetal heart rate testing before and throughout labor. Neonatal safety was assessed by Apgar score, arterial or venous pH of cord blood, and blood glucose level during the first 48 hours. Analysis used Student t test for continuous variables, Kruskal-Wallis test for ordinal data, and chi2 for categoric variables.

RESULTS

Strict success was achieved in 10 of 18 mifepristone patients (55%) evaluated for Bishop score on day 2 versus 8 of 29 placebo patients (27.5%) (P=.004). Extended success was achieved in 33 mifepristone patients (80.5%) and 21 placebo patients (50.0%) (P=.004). There were no statistical differences with regard to number of cesareans or fetal and neonatal safety.

CONCLUSION

Mifepristone proved effective for cervical ripening and reduced the time to delivery compared with placebo, but it did not improve the rate of cesarean. Our study did not include enough pregnancies to reach conclusions about fetal or neonatal safety.

Interference of the antihormone RU486 in the determination of testosterone and estradiol by enzyme-immunoassay

The antihormone RU486 (mifepristone, 11beta-(4-dimethylaminophenyl)-17beta-hydroxy-17alpha-(prop- 1-ynyl)-estra-4,9-dien-3-one) is currently used in many endocrinological studies and in clinical practice as a contraceptive agent. The results presented here indicate that the synthetic steroid RU486 may interfere in determinations of testosterone and estradiol when using some commercial kits. Although the cross reactivity is low (0.30% for testosterone and 0.16% for estradiol), in animal experiments RU486 doses higher than 5 mg/kg may produce false positive results in the estimation of plasma testosterone (specially in castrated male or female mice) or estradiol concentrations, even in samples obtained 48 h after the administration of this antihormone.

RU 486 blocks and fluoxetine augments progesterone-induced prolactin secretion in monkeys

Progesterone (P) stimulates prolactin secretion through an unknown neural mechanism in estrogen (E)-primed female monkeys. Serotonin also stimulates prolactin secretion and this laboratory demonstrated that E induces nuclear progestin receptors (PR) in serotonin neurons. Thus, PR in serotonin neurons could transduce the action of P on prolactin secretion. Studies were performed to determine (1) whether blocking nuclear PR would block P-induced prolactin secretion and conversely; (2) whether increasing serotonin concentrations in the synapse would augment P-induced prolactin secretion. In both studies, female monkeys were spayed, adapted to a vest and tether remote sampling system and catheterized prior to experiments. Monkeys received 2 E-filled silastic implants (3.0 cm) 1-3 weeks prior to study. P (20 mg) in corn oil was injected (s.c.) to transiently increase prolactin secretion. In both studies, each monkey served as its own control. To block nuclear PR and not membrane PR, RU 486 (2 mg/kg, i.m.) or ethanol (control) was administered with the P injection. Relative to the P injection, blood samples were taken twice daily from -30 to +24 h, then every 4 h from +36 to +48 h and once at +65 h. To increase serotonin in the synapse, the serotonin reuptake inhibitor, fluoxetine (5 mg/day, i.v.), was infused for 4 weeks. P was injected during the week of vehicle infusion and during the last week of fluoxetine infusion. Blood samples were obtained twice daily prior to and following P treatment. Prolactin, E, P and RU 486 concentrations were determined by RIA. RU 486 completely blocked the P-induced prolactin surge (n = 3). In addition, fluoxetine significantly increased prolactin secretion during the P-induced prolactin peak compared to equal time points during saline infusion (n = 5). These data indicate that P induces prolactin via a genomic mechanism and not through a membrane action. The data also support a pivotal role for serotonin in the neural regulation of P-induced prolactin secretion.

Pharmacokinetics of mifepristone after low oral doses

Relatively low doses of the antiprogestin mifepristone (RU 486) have recently proven to be efficient for a variety of possible clinical uses of the drug. However, the pharmacokinetics after low single oral doses have not been characterized. We evaluated the pharmacokinetics of mifepristone following single ingestion of 2 and 25 mg in five women as well as repeated ingestion of 8 mg in two women. Maximal serum concentrations were reached rapidly (within 0.5-2 h) with all doses used. Serum mifepristone concentrations were proportional to the oral doses taken. The mean (+/- SD) areas under the concentration curves (AUCs) (0-24 h) were 1134 (+/- 144), 4846 (+/- 64), and 17,015 (+/- 4,421) h x ng/mL following 2, 8, and 25 mg doses, respectively. No cumulative increases in serum concentrations were detected with prolonged daily administration of 8 mg of mifepristone. The study subjects appeared to vary in their ability to metabolize mifepristone, as two different half-lives (t1/2) emerged after both 2 and 25 mg single doses (24.2 +/- 0.6 [SD] h for three subjects; and 44.4 +/- 1.8 [SD] h for two subjects). We conclude that within the dose range of 2-25 mg/day, the pharmacokinetics of mifepristone are linear, unlike those seen following ingestion of higher daily doses. Keeping in mind previously published data on the biological effects of low dose mifepristone administration, these data infer that certain effects of the drug, such as inhibition of ovulation, might be achieved at serum concentrations of approximately 100 ng/mL.

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.

Antiovulatory actions of RU 486: the pituitary is not the primary site of action in vivo

Continuous administration of RU 486 impairs follicular development and inhibits ovulation in women. Yet, the mechanism of ovulation inhibition remains unknown. To characterize the mechanism(s) of ovulation inhibition, we studied six regularly menstruating cynomolgus monkeys for three consecutive (control-rest-treatment) cycles. Monkeys received 1 mg/kg.day RU 486 in between cycle days 2-22. Basal and GnRH-stimulated (1 and 50 micrograms GnRH, iv, 2 h apart) secretion of LH and FSH was assessed using serial blood samples (every 15 min for 12 h) collected on cycle day 10. Serum levels of estradiol (E2), progesterone (P4), RU 486, cortisol, LH, FSH, and PRL were analyzed by RIAs, the bioactivity of LH was assessed using a mouse Leydig cell assay. The mean cycle length was prolonged by RU 486 treatment from 31.8 to 69.8 days (P = 0.008). During RU 486 treatment, patterns of E2 secretion varied considerably; the mean +/- SD E2 level was 204 +/- 139 pmol/L. LH peaks and P4 profiles compatible with luteal function were seen only before resumption of menstruation. However, one monkey had an increase in P4 after the GnRH challenge-induced LH secretion. Basal levels of LH varied between suppressed and apparently normal values, whereas basal FSH seemed little affected by RU 486 treatment. In two monkeys with E2 secretion indicative of normal follicular development, minor peaks of LH, but no rises in serum P4, were seen. The ratio of bioactive/immunoactive LH was reduced in these monkeys during RU 486 treatment compared to that during the washout period of the treatment cycle. Surprisingly, the pituitary responsiveness to acute GnRH challenge was not affected by RU 486 administration. The individual levels of RU 486 were similar during the treatment period (mean, 40 nmol/L). A resumption of ovulatory cycles occurred when RU 486 concentrations were below 2.5 nmol/L. We conclude that in cynomolgus monkeys, inhibition of ovulation by RU 486 occurs mainly at the level of the hypothalamus, with possible additional effects on the granulosa cell function and alterations of LH bioactivity.

Tissue and serum levels of steroid hormones and RU 486 after administration of mifepristone

The present study was designed to examine the effect RU 486 administration on steroid hormone levels in serum and decidua. Sixty women at 6-7 weeks gestation were divided into three groups. The first group took a placebo 24 hours before interruption of pregnancy. The other two groups took 200 mg mifepristone 12 and 24 hours before the surgical procedure, respectively. The concentrations of steroids and mifepristone were measured by radioimmunoassay or high performance liquid chromatography. Mifepristone treatment increased the levels of estradiol, cortisol and testosterone in serum and decidual cytosol (p < 0.05 or p < 0.01). A minor elevation in progesterone level was observed but was not statistically significant. The tissue levels of progesterone, estradiol and testosterone were much higher than the serum levels, whereas RU 486 concentration in the tissue was only one-third of the serum level. In addition, the RU 486 level in decidual cytosol was of the same order as that of progesterone. This competitive concentration was not achieved in chorionic villi in our previous observation, explaining why mifepristone exerts its predominant effect on decidua rather than villi. It is concluded that RU 486 reached an effective inhibitory concentration in decidua and had significant effects on the endocrine milieu.

Effects of the glucocorticoid antagonist RU 486 on pituitary-adrenal function in patients with anorexia nervosa and healthy volunteers: enhancement of plasma ACTH and cortisol secretion in underweight patients

To further explore whether the hypercortisolism of anorexia nervosa reflects an alteration in the set point for corticotropin-releasing hormone (CRH) secretion or is a manifestation of glucocorticoid resistance, we examined plasma ACTH and cortisol responses to the competitive glucocorticoid antagonist RU 486 (10 mg/kg, p.o. at 8.00 h) versus placebo (PBO) in 7 healthy female volunteers and 8 patients with DSM-III-R anorexia nervosa, all of whom were studied while underweight [64.3 +/- 2.1% average body weight (ABW), mean +/- SE] and 5 of whom were restudied longitudinally following refeeding (> or = 85% ABW, mean 87.4 +/- 0.4% ABW). Blood samples were obtained from 16.00 to 16.30 h and from 4.00 to 8.00 h following dosing. Underweight anorexics were significantly hypercortisolemic by 24 h urinary free cortisol excretion compared with controls (239 +/- 37 vs. 119 +/- 12 nmol/day, p < 0.01). Both controls and underweight anorexics had robust early morning (4.00-8.00 h) plasma cortisol responses to RU 486 (465 +/- 61 and 719 +/- 49 nmol/l) compared with PBO (370 +/- 52 and 451 +/- 31 nmol/l; p < 0.02 and p < 0.01, respectively). The underweight anorexics showed a significant mean early morning plasma ACTH response to RU compared with placebo (3.28 +/- 0.63 vs. 2.01 +/- 0.24 pmol/l, p < 0.05), while the controls showed a trend toward an increase in mean plasma ACTH after RU (3.11 +/- 0.36 pmol/l) compared with PBO (2.31 +/- 0.41 pmol/l, p < 0.13); plasma ACTH means were greater on the RU day than the placebo day at 20 of 25 sampling points (p < 0.001). However, the increment in ACTH on the RU day compared to the placebo day was greater in the underweight anorexics at the first 20 of 25 consecutive time points of the early morning sampling period (p < 0.001). Moreover, underweight anorexics showed a significant plasma ACTH and cortisol response to RU 486 at 16.00-16.30 h (8-8.5 h following administration), while the controls showed no significant response of plasma ACTH or cortisol at this time. When restudied following weight recovery, anorexic patients showed reductions in 24-hour urinary free cortisol excretion (to 191 +/- 40 nmol/day) which were no longer significantly elevated compared with control values.(ABSTRACT TRUNCATED AT 400 WORDS)

Response to intermittent RU486 in women

OBJECTIVE

To determine the effects of intermittent administration of the antiprogestin RU486 on ovarian function.

DESIGN

Three different regimens of RU486 were tested.

PARTICIPANTS

Nine healthy regularly menstruating volunteers protected by an intrauterine device or surgical sterilization.

INTERVENTIONS

Two groups of three women each received 10 mg or 50 mg RU486 at weekly intervals for 5 weeks. Another three women received 50 mg RU486 for 3 consecutive days at 10-day intervals for 80 days.

MAIN OUTCOME MEASURES

Serum E2, P and RU486 levels. Ovarian ultrasound (US) and serum LH and FSH in select subjects.

RESULTS

The predominant effect was partial inhibition of E2 secretion and suppressed P levels. During a total aggregate of 16 treatment months, there were seven episodes of elevated P levels; however, US did not always indicate the occurrence of normal ovulation.

CONCLUSION

Intermittent RU486 administration can interfere with normal follicular development and function, but its clinical application may require a more effective dose and/or timing of administration.

Estrogen action in the reproductive tract of rhesus monkeys during antiprogestin treatment

We previously reported that RU486 can reverse progesterone (P)-induced suppression of the estrogen receptor (ER) in the uterus of pregnant rhesus monkeys, but we did not determine whether estrogen (E) could act through its receptor in the presence of P and RU486. To pursue this question, we treated spayed rhesus monkeys with various hormonal regimens and evaluated the effects of E in the oviduct and endometrium, with and without RU486 treatment, on ER and progestin receptor (PR) levels, morphology, apoptosis, and degree of proliferation. The latter was assessed immunocytochemically with a monoclonal antibody (Ki-67) against a nuclear antigen present only in proliferating cells. Animals were treated for 2 weeks with 17 beta-estradiol (E2) and then for 2 weeks with E2 plus P to produce a regressed oviduct and a secretory endometrium. The animals were then treated for 2 more weeks with four different treatments, as follows: I) E2, P, and vehicle; II) E2 and vehicle; III) E2, P, and RU486; and IV) E2 and RU486 (n = 4 each). In group I, menstruation did not occur, and the endometrium exhibited stromal cell enlargement, extensive development of the spiral arteries, few Ki-67-positive cells, and low levels of ER and PR. Oviducts in group I remained regressed, Ki-67-positive epithelial cells were few, and levels of ER and PR were low. In contrast, in groups II, III, and IV, the oviducts had responded to E2 and were fully ciliated and secretory, with elevated levels of ER and nuclear PR. All animals in these three groups menstruated and then regenerated their endometrium. The regenerated endometria expressed elevations in ER, nuclear PR, and epithelial Ki-67 index. However, the endometria of RU486-treated monkeys in groups III and IV had significantly more epithelial cell death by apoptosis, increased stromal cell compaction, and fewer Ki-67-positive stromal cells than in the E2 controls (group II). In group IV, RU486 caused a significant decrease in endometrial weight. Thus, RU486 blocked P action and allowed E2 to act in a normal fashion in the oviduct and endometrium on several end points, but it also had antiproliferative effects that opposed E2 action, especially in the endometrium.

[Radioreceptor assay for determination of the anti-progestogen, RU-486 and its active metabolites in the blood]

RU-486 is an antiprogesterone 19-norsteroid with high binding affinity for the progesterone receptor. It can be used with success for termination of early human pregnancy. Since the metabolites of RU-486 are often biologically active, their concentrations in blood can also have clinical significance. We have developed a rapid sensitive radio receptor assay for determination of RU-486 and its active metabolites. Human myometrium progesterone receptor was used as binding protein. The assay is based on the competitive replacement of 3H-ORG-2058 by the active molecular fraction of RU-486 present in the serum. The analytical parameters of this assay are the followings: intraassay percent of coefficient of variation (CV%) is ranged between 7.6 and 10.4%. The interassay CV% was from 7.1 to 16.3. The sensitivity of the receptor assay was 8.7 pmol/tube and the acceptable range was between 10 and 120 pmol/tube. The recovery ranged between 95 and 122% (r = 0.983). These parameters are suitable for the requirement of radioligand binding techniques based on the immunoassays.

Antiprogesterone, RU 486, facilitates parturition in cattle

RU 486, a potent progesterone antagonist with high affinity for progesterone receptor, was used alone or in combination with relaxin in late pregnant cattle to determine its effect on induction of parturition. Cross-bred beef cattle were bred by artificial insemination. An indwelling cannula was inserted into a jugular vein on day 269 (expected term = day 283) for repeated blood sample collection. On day 277, the cattle were assigned randomly to three groups (n = 6 each): group 1 received RU 486 (2 mg/kg BW, im) at 0800 h on days 277 and 278; group 2 received the same RU 486 treatment plus 3000 U relaxin, injected sc at 0800 h on day 278; and group 3 served as controls and received vehicle injection. Parturition occurred 55 h after treatment in group 1 and 53 h after treatment in group 2 compared with 210 h in the controls (P less than 0.01). The calves from treated groups were vigorous at birth, and their birth weights (32 and 33 kg in groups 1 and 2) were less than those of control calves (38 kg; P less than 0.01). There was no incidence of difficult birth (dystocia) with RU 486 treatment compared with that in the controls. Placenta delivery averaged 6.5 h after birth in both RU 486-treated groups and did not differ from the control value (5 h). Plasma progesterone concentrations averaged 8.2 ng/ml during the pretreatment period for all animals. Progesterone started to decrease markedly by 1200 h on day 278, dropped to about 4 ng/ml by 2400 h that same day, and was at basal levels on day 279, the day of calving, in two hormone-treated groups. In sharp contrast, progesterone was maintained at about 6 ng/ml in placebo-treated controls during this period and did not decrease to basal levels until 2 days before parturition on day 286 (P less than 0.01). Peak RU 486 in plasma was 7.2 ng/ml after the first injection and 14.3 ng/ml after the second injection, and averaged 7.9 ng/ml on the day of induced calving (day 279). Peak relaxin was 4.1 ng/ml after hormone injection. The results indicate that RU 486 alone or combined with relaxin precisely controlled the time of parturition in cattle in late pregnancy. Such treatment can be used to facilitate parturition and increase survival rates of neonatal calves without detrimental effects of dystocia, retention of placenta, and delayed postpartum fertility.

Automated direct assay system for RU38486, an antiprogesterone-antiglucocorticoid agent, and its metabolites using high performance liquid chromatography

An automated direct assay system using high performance liquid chromatography was developed for the measurement of RU38486 and its three metabolites (RU42698, RU42848, RU42633) in human serum. Serum concentrations of these compounds were measured up to 144 h following single oral administration of 200 (200 mg group, n = 3) or 400 mg (400 mg group, n = 3) of RU38486 to healthy female volunteers. The serum half-lives (200 mg group-400 mg group) of RU38486, RU42698, RU42848 and RU42633 were 31.8-33.1 h, 41.2-39.3 h, 33.9-36.6 h and 29.2-36.6 h, respectively. Our system could quantify them easily and simultaneously, and was considered to be valuable in studies on the relationship between the pharmacokinetics and the clinical effects of RU38486.

The effect of RU 486 administered during the early luteal phase on bleeding pattern, hormonal parameters and endometrium

The purpose of the present study was to investigate the effect of a single dose of RU 486 administered very early in the secretory phase on endometrial development and levels of progesterone receptors, on plasma levels of gonadotrophins and ovarian hormones and on the pattern of menstrual bleeding. Twenty-four regularly menstruating subjects participated and were studied during a control, a treatment and a follow-up cycle. In the treatment cycle, a single dose of 200 mg RU 486 was given in the evening of the second day after the urinary LH peak. Plasma was collected from cycle day 10 until menstruation in both control and treatment cycles. The lengths of the control, treatment and follow-up cycles were equal. Three of the subjects had slight vaginal bleeding in association with RU 486 intake which, however, did not disturb their normal menstrual rhythm. Plasma levels of oestradiol, progesterone and FSH were not affected in the treatment cycle, whereas LH levels increased slightly. The elimination half-life of RU 486 was 28.6 h. An endometrial biopsy was taken 12, 36 or 84 h (LH + 3, LH + 4 and LH + 6) after drug intake (eight subjects in each group) and another biopsy was taken on the corresponding day in the control cycle. The specimens were assessed by morphometric analysis and for cytosolic progesterone receptor concentrations. Endometrial biopsies taken 12 h (on LH + 3) after RU 486 intake contained significantly (P less than 0.001) lower levels of cytosolic progesterone receptors than in the control cycle, but levels at 36 and 84 h were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma levels of SP1-like immunoreactive material (SP1) and progesterone throughout pregnancy and following RU 486-induced early abortion in the cynomolgus monkey (Macaca fascicularis)

A human-SP1 immunoassay was used to detect SP1-like material (SP1) in the plasma of cynomolgus monkeys. In 27 females remaining non-pregnant during a mating period of 4 months, SP1 was occasionally detected at a mean concentration of 2.5 ng/ml. In 14 non-pregnant females of subsequent proven fertility, SP1 was detected 20 days following unfertile mating at a mean concentration of 4.8 ng/ml in 86% of cycles. At day 20 of proven pregnancies, SP1 was at 12 ng/ml in 93% of these animals. SP1 levels during pregnancy increased in two steps, a slow rise between days 20 and 50, followed by an abrupt rise between days 50 and 60 and afterwards a plateau at 600 ng/ml. Seven other pregnant monkeys received 10 mg/kg of the antiprogestin RU 486 at 28 days. Four aborted and the others continued their gestation. SP1 was always dramatically depressed by this treatment; in animals with abortion failure, it remained at a low concentration for 3 months, then the normal concentration range was recovered. The assay of SP1-like material does not allow early diagnosis of pregnancy, however, it remains interesting as a follow-up parameter after 60 days. Also, antiprogestins appear to be useful tools to analyse the metabolism of SP1.

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.