Comparative estrogenicity of endogenous, environmental and dietary estrogens in pregnant women II: Total estrogenicity calculations accounting for competitive protein and receptor binding and potency.

Evaluating the biological significance of human-relevant exposures to environmental estrogens involves assessing the individual and total estrogenicity of endogenous and exogenous estrogens found in serum, for example from biomonitoring studies. We developed a method for this assessment by integrating approaches for (i) measuring total hormone concentrations by mass spectrometry (Fleck et al., 2018), (ii) calculating hormone bioavailable concentrations in serum and, (iii) solving multiple equilibria between estrogenic ligands and receptors, and (iv) quantitatively describing key elements of estrogen potency. The approach was applied to endogenous (E1, E2, E3, E4), environmental (BPA), and dietary Genistein (GEN), Daidzein (DDZ) estrogens measured in the serum of thirty pregnant women. Fractional receptor occupancy (FRO) based estrogenicity was dominated by E1, E2 and E3 (ER-α, 94.4-99.2% (median: 97.3%), ER-ß, 82.7-97.7% (median: 92.8%), as was the total response (TR), which included ligand specific differences in recruitment of co-activator proteins (RCA). The median FRO for BPA was at least five orders of magnitude lower than E1, E2 and E3, and three orders of magnitude lower than the fetal derived E4 and GEN and DDZ. BPA contributed less than 1/1000th of the normal daily variability in total serum estrogenicity in this cohort of pregnant women.

Differential effect of the 17ß-aminoestrogens prolame, butolame and pentolame in anxiety and depression models in rats.

Estrogens of clinical use produce consistent antidepressant- and anxiolytic-like effects in animal models of menopause. Regulation of the hypothalamic-pituitary-adrenal (HPA) or stress axis, has been proposed as a pathway through which estrogens improve affective-like behaviors. Anticoagulant 17ß-aminoestrogens (17ß-AEs) butolame and pentolame mimic some effects of estradiol (E2), i.e., on female rodent sexual behavior, with opposite actions on coagulation. However, their psychoactive actions have not been explored. On the basis of similitude with E2's effects, we hypothesized that these 17ß-AEs would induce anxiolytic- and antidepressant-like effects, which would be reflected in a reduction of activity in the HPA axis. In ovariectomized female rats, chronic treatment with prolame (60 µg/kg), butolame (65 µg/kg) and pentolame (70 µg/kg) reduced anxiety-like behavior in the elevated plus maze (evidenced by an increase in time in open arms, E2 (40 µg/kg) +176%; prolame +201%; butolame, +237%; and pentolame +295%, in comparison to the control vehicle group 100%). Pentolame also decreased significantly anxiety-like behavior in the burying behavior test. Prolame and E2 produced a significantly antidepressant-like action, which was not induced by butolame and pentolame. Behavioral effects of 17ß-AEs (and E2) on anxiety and depression did not follow the same pattern than corticosterone or E2 levels; they also were associated to changes in locomotor activity, evaluated by the open field test. These results constitute the first evidence of specific and selective actions of butolame and pentolame as anxiolytics for females with a hypoestrogenic condition. Results also confirm the potential of prolame as an antidepressant steroid with equivalent actions to E2. Psychoactive properties of 17ß-AEs in combinations with reduced adverse effects on coagulation, suggest that 17ß-AEs may be a good alternative replacement therapy for women with symptoms associated with menopause.

Ultra high performance liquid chromatography/tandem mass spectrometry based identification of steroid esters in serum and plasma: an efficient strategy to detect natural steroids abuse in breeding and racing animals.

During last decades, the use of natural steroids in racing and food producing animals for doping purposes has been flourishing. The endogenous or exogenous origin of these naturally occurring steroids has since remained a challenge for the different anti-doping laboratories. The administration of these substances to animals is usually made through an intra-muscular pathway with the steroid under its ester form for a higher bioavailability and a longer lasting effect. Detecting these steroid esters would provide an unequivocal proof of an exogenous administration of the considered naturally occurring steroids. A quick analytical method able to detect at trace level (below 50 pg/mL) a large panel of more than 20 steroid esters in serum and plasma potentially used for doping purposes in bovine and equine has been developed. Following a pre-treatment step, the sample is submitted to a solid phase extraction (SPE) before analysis with UPLC-MS/MS. The analytical method's efficiency has been probed through three different in vivo experiments involving testosterone propionate intra-muscular administration to three heifers, 17-estradiol benzoate intra-muscular administration to a bull and a heifer and nandrolone laurate intra-muscular administration to a stallion. The results enabled detecting the injected testosterone propionate and 17-estradiol benzoate 2 and 17 days, respectively, post-administration in bovine and nandrolone laurate up to 14 days post-administration in equine. The corresponding elimination profiles in bovine serum and equine plasma have been established. The first bovine experiment exhibited a maximal testosterone propionate concentration of 400 pg/mL in one of the three heifer serum within 5h post-administration. The second bovine experiment reported a maximal 17-estradiol benzoate concentration of 480 pg/mL in the same matrix recorded 9 days after its administration. The last equine experiment resulted in a maximal nandrolone laurate concentration of 440 pg/mL in horse plasma 24h after administration.

Determination of cymipristone in human plasma by liquid chromatography-electrospray ionization-tandem mass spectrometry.

A rapid, specific and sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated for determination of cymipristone in human plasma. Mifepristone was used as the internal standard (IS). Plasma samples were deproteinized using methanol. The compounds were separated on a ZORBAX SB C(18) column (50 mm x 2.1 mm i.d., dp 1.8 microm) with gradient elution at a flow-rate of 0.3 ml/min. The mobile phase consisted of 10 mM ammonium acetate and acetonitrile. The detection was performed on a triple-quadruple tandem mass spectrometer by selective reaction monitoring (SRM) mode via electrospray ionization. Target ions were monitored at [M+H](+)m/z 498-->416 and 430-->372 in positive electrospray ionization (ESI) mode for cymipristone and IS, respectively. Linearity was established for the range of concentrations 0.5-100 ng/ml with a coefficient correlation (r) of 0.9996. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.5 ng/ml. The validated method was successfully applied to study the pharmacokinetics of cymipristone in healthy Chinese female subjects.

Estrogen and tibolone metabolite levels in blood and breast tissue of postmenopausal women recently diagnosed with early-stage breast cancer and treated with tibolone or placebo for 14 days.

Unlike estrogens plus progestagens, tibolone, a selective tissue estrogenic activity regulator, does not increase breast tenderness and mammographic density. To elucidate this, serum and breast levels of tibolone and estrogenic metabolites are measured. Postmenopausal women (n = 102) with early-stage, ER(+ve), primary breast cancer received tibolone or placebo for 14 days in an exploratory, double-blind, randomized trial (STEM carcinoma tissue). Baseline and presurgery sera were collected; tumor tissues were obtained at surgery. E(1) (estrone), E(2) (estradiol), E(1)S (estrone-sulfate), tibolone-its nonsulfated, monosulfated, and disulfated 3-hydroxymetabolites-and Delta(4)-tibolone were measured by validated gas chromatography and mass spectrometry and liquid chromatography with tandem mass spectrometry assays. More than 12 hours after the final dose, serum E(1), E(2), and E(1)S levels were unchanged with placebo, whereas tibolone significantly increased E(1)S and the E(1)S/(E(1) + E(2)) ratio. In tumors, E(1) and E(2) levels were higher than in serum, and E(1)S levels were lower, with placebo and tibolone administration. The percentage of E(1)S was about 90% in serum and 16% in tissue. Tibolone did not affect tissue levels of endogenous estrogens. Serum levels of estrogenic 3alpha- and 3beta-hydroxytibolone, progestagenic/androgenic Delta(4)-tibolone, and monosulfate metabolites were low. Serum 3alphaS,17betaS-tibolone and 3 betaS,17betaS-tibolone levels were 250 and 52 ng/mL, respectively. Tumor levels of 3alpha- and 3beta-hydroxytibolone and Delta(4)-tibolone were higher than in serum, but disulfate levels were lower. The percentage of sulfated tibolone metabolites was 99% in serum and 96% in tumor. Serum metabolite patterns of estradiol and tibolone are different from those in tissues and are compatible with neutral effects of tibolone on breast Ki67 expression.

Intrauterine release of progesterone antagonist ZK230211 is feasible and results in novel endometrial effects: a pilot study.

BACKGROUND: Continuous administration of progesterone antagonists (PAs) results in endometrial suppression and amenorrhoea in several model systems. We compared the effects of intrauterine release of a highly specific PA, ZK230211, to those of a progestin using the levonorgestrel-releasing intrauterine system (LNG-IUS). METHODS: Forty-two women were randomly fitted with an IUS releasing either ZK230211 at a rate 1, 4 or 8 microg/24 h (ZK-IUS) or LNG (at 20 microg/24 h, LNG-IUS) at 4-8 weeks before hysterectomy. Bleeding patterns, endometrial morphology and content of ZK230211, and various immunohistochemistries (IHCs) were evaluated. RESULTS: Days of bleeding and spotting were unchanged by the use of ZK-IUSs but were increased by LNG-IUS (P < 0.01). ZK230211 was measurable in all endometrial specimens. Endometrium was partly suppressed in 9-30% of women following the use of ZK-IUSs, and in 67% after LNG-IUS. IHCs for Ki-67 and phosphorylated histone H3 were not suggestive of proliferative activity in any group. Compared to LNG, progesterone receptor (PR) was increased following ZK230211 in surface epithelium (all three doses P < 0.01-P < 0.05) and stroma at 4 microg/24 h (P < 0.05). Although low, androgen receptor staining was higher in endothelial epithelium following LNG than ZK230211 (P < 0.05). Insulin-like growth factor-binding protein-1 (IGFBP-1) was detectable only following LNG (P < 0.0001). CONCLUSIONS: Short-term intrauterine release of ZK230211 did not change bleeding patterns or result in endometrial suppression. Expression of proliferation markers was low following the use of both IUSs. Absence of IGFBP-1 and increase in PR reflect the PA effects of ZK230211.

Biowaivers for oral immediate-release products: implications of linear pharmacokinetics.

Bioequivalence of drug formulations plays an important role in drug development. Recently, the Biopharmaceutical Classification System (BCS) has been implemented for the purpose of waiving bioequivalence studies on the basis of the solubility and gastrointestinal permeability of drug substance. Using the rationale of the BCS, it can be argued that biowaivers can, however, also be granted on the basis of standard pharmacokinetic data. If a drug exhibits dose-linear pharmacokinetics and a sufficiently fast dissolution profile, it can be concluded that this drug appears to pose no problem with respect to absorption. It should be noted that a change of an immediate-release tablet formulation can only lead to a deviating rate and/or extent of absorption when release of the drug from the formulation is altered. Logically, the dissolution profiles of the different formulations should be equal to guarantee bioequivalency. Thus, both BCS and the alternative linear pharmacokinetics approach require an evaluation of dissolution profiles. The justification of BCS is found in the permeability classification of the compound, while those of the linear pharmacokinetics lie in the apparent lack of a permeability problem. For example, in this context P-glycoprotein-transported drugs form an interesting class of compounds, which may be treated likewise when complying to the aforementioned requirements. Furthermore, poorly soluble compounds may be less troublesome than expected. It is shown that linear kinetics can be explained by the solubilising activity of, for example, bile salts. In this instance, linear pharmacokinetics shows that elevated doses do not appear to exhibit a limiting role on the dissolution. Hence, a change in formulation without any effect on the dissolution profile is not expected to cause a change in availability. It is clear that the formulations to be compared should not contain excipients that display an effect on (presystemic) drug metabolism.

Pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT) delivery using subdermal implants in healthy men.

We studied the pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT), a potent synthetic androgen, administered by subdermal implants. The implants contained 112 +/- 4 mg of MENT acetate in a polyethylene vinyl acetate copolymer. MENT acetate released from the implants is rapidly hydrolyzed to MENT in vivo. Fifteen healthy Finnish men were randomized to have either one, two, or four implants inserted in the medial aspect of the upper arm. The implants remained in place for 4 weeks. Blood samples were obtained before implant insertion, 1, 2, 3, and 4 weeks after insertion, and 1 and 2 weeks after removal. Serum MENT concentrations were determined by gas chromatography with mass selective detection. The MENT levels attained in each implant group remained at a steady level during the 4 weeks of implant use. The mean steady state MENT concentrations in the one, two, and four implant groups were 0.6, 1.4, and 2.3 nmol/L, respectively. Serum MENT concentrations during implant use were clearly dose dependent; the between-subject effect of implants as well as the differences between each pair of groups were all statistically significant. The release rate of MENT from one, two, and four implants was calculated to be approximately 0.3, 0.8, and 1.3 mg/day, respectively. This study suggests that MENT acetate implants are a promising method for long-term androgen administration in hypogonadism and male contraception.

PIP: The authors studied the pharmacokinetics of 112 +or- 4 mg of MENT acetate in a polyethylene vinyl acetate copolymer. MENT acetate released from the implants is rapidly hydrolyzed to MENT in vivo. 15 healthy Finnish men were randomized to have either 1, 2, or 4 implants inserted in the medial aspect of the upper arm. The implants remained in place for 4 weeks. Blood samples were obtained before implant insertion, 1, 2, 3, and 4 weeks after insertion, and 1 and 2 weeks after removal. Serum MENT concentrations were determined by gas chromatography with mass selective detection. The MENT levels attained in each implant group remained at a steady level during the 4 weeks of implant use. The mean steady state MENT concentrations in the 1, 2, and 4 implant groups were 0.6, 1.4, and 2.3 nmol/l, respectively. Serum MENT concentrations during implant use were clearly dose dependent; the between-subject effect of implants as well as the differences between each pair of groups were all statistically significant. The release rate of MENT from 1, 2, and 4 implants was calculated to be approximately 0.3, 0.8, and 1.3 mg/day, respectively. The study suggests that MENT acetate implants are a promising method for long-term androgen administration in hypogonadism and male contraception.

[Determination of the progesterone antagonist lilopristone in serum by RP-HPLC].

To 1.0 ml of serum containing lilopristone were added RU486 solution (internal standard, IS) and 1 ml of 1.0 mol.L-1 NaOH. The mixture was extracted with diethyl ether for 2 times. After extraction, the combined organic phase was evaporated to dryness and the residue was dissolved in the mobile phase and washed with petroleum ether. After centrifugation, 20 microliters of the lower layer was subjected to HPLC. A muBondapak-C18 (10 microns) column (30 cm x 3.9 mm) was used and the column temperature was kept at 50 degrees C. The flow rate of mobile phase (methanol-dichloromethane--0.01 mol.L-1 phosphate buffer, pH 4.0, 67:5:28 v/v) was 1.1 ml.min-1 and UV detection was performed at 302 nm. The retention times of lilopristone and IS were 6.85 and 9.07 min respectively and the detection limit was 10 ng.ml-1 (S/N > or = 4) serum. The extraction recoveries of lilopristone and IS were over 85%. The relative standard deviations were 2.21 to 4.23%. This method has been applied to study the pharmacokinetic of lilopristone in rats.

Measurement of steroid hormones in plasma by isocratic high performance liquid chromatography coupled to radioimmunoassay.

The study of steroidal profiles requires simultaneous determinations of various steroid hormones that cannot be appropriately carried out with the conventional routine immunoassays. Moreover, there are several trials for which the assessment of multiple steroids from a single serum sample is mandatory. In this paper we describe a procedure for simultaneously measuring steroid hormones using a unified solid phase extraction which allows the measurement of both unconjugated and conjugated steroids from 1 ml of sample and a combination of HPLC with isocratic elution followed by RIA. The entire procedure was preliminary carried out for the measurement of testosterone, dehydroepiandrosterone and its sulphated conjugate, androstenedione and 17 hydroxyprogesterone. The use of this technique allows precise and accurate measurements of steroid profile with a single serum aliquot and could be helpful in the diagnosis of various form of endocrine disorders.

Antiarrhythmic, electrophysiological and haemodynamic effects of prolonged oral dosing with Org 7797 in the anaesthetized rat.

The antiarrhythmic, electrophysiological and haemodynamic effects of chronic oral administration of Org 7797 ((16 alpha,17 beta)-17-methylamino-oestra-1,3,5(10)-triene-3, 16-diol-(Z)-2-butonedioate) were studied in rats. During dosing (10 mg kg-1 twice a day for 10 days) no effects on the electrocardiogram, monitored in conscious animals, were observed despite modest reductions (15-18%) in the maximum rate of depolarization of papillary muscle excised 1 or 6 h after completion of the dosing regime. Following anaesthesia, Org 7797 reduced the severity of arrhythmias induced by coronary artery occlusion and prevented the accompanying decrease in the ventricular fibrillation threshold (VFT) at 1 h after completion of dosing. By 6 h the effect on VFT had waned but protection against ischaemia-induced arrhythmias was retained despite a substantial decrease in Org 7797 plasma levels. Drug treatment did not modify arterial blood pressure, heart rate or stroke volume. We conclude that Org 7797 given chronically via the oral route exerts antiarrhythmic actions which may, at least in part, be due to sodium-channel block. In addition, our results suggest the presence of an active metabolite. The protective effects of Org 7797 were seen in the absence of electrocardiographic or haemodynamic changes suggesting that multiple oral doses of Org 7797 do not compromise normal cardiac function.

Radioimmunoassay of 7 alpha-methyl-19-nortestosterone and investigation of its pharmacokinetics in animals.

A method for the measurement of 7 alpha-methyl-19-nortestosterone (7MENT) in serum/plasma by radioimmunoassay (RIA) is described. The antiserum, raised against 7 alpha-methyl-19-nortestosterone-3-O-oxime-bovine serum albumin, had a low titer (final dilution = 1:4500) and low affinity (Ka = 1.17 x 10(9) l/mol) but showed little or no cross-reactivity with several of the steroids tested. The sensitivity of the RIA was 28.2 pg/ml and the mean recovery of added cold steroid was 86 to 100%. Intra- and inter-assay coefficients of variation ranged from 4.3 to 7.3% and 7.3 to 8.4%, respectively. This RIA was used to follow plasma 7MENT levels after a single i.v. injection of the steroid in rats and rabbits. The metabolic clearance rates (MCR) of 7MENT as determined from the plasma disappearance curve for rats and rabbits were 50 l/day and 336 l/day, respectively. The MCR of 7MENT in rats and rabbits lies in the same range as for testosterone. When compared to other nortestosterone derivatives such as norethisterone, 7MENT is metabolized relatively faster.

Distribution of RU 486 and its demethylated metabolites in humans.

The concentrations of RU 486 and its demethylated metabolites were determined by RIA in samples of myometrium, abdominal adipose tissue, and serum, which were collected at hysterectomies performed 12-15 h after oral administration of 200 mg RU 486. The RU 486 concentrations in myometrium were similar in the five women studied, with a mean of 148 +/- 58 (+/- SD) ng/g (344 +/- 135 pmol/g). The adipose tissue RU 486 levels varied more, the mean concentration being 447 +/- 191 ng/g (1041 +/- 445 pmol/g). The serum RU 486 concentrations ranged from 175-899 ng/ml [mean, 396 +/- 259 ng/mL (922 +/- 603 nmol/L)]. In these women the nonprotein-bound fraction of [6,7-3H]RU 486 varied from 1.4-3.1% (mean, 2.3%). The approximate concentrations of the combined mono- and didemethylated metabolites of RU 486 were 1.4, 3.1, and 5.2 times higher in adipose tissue, myometrial tissue, and serum, respectively, than those of the parent RU 486. In vitro, rapid and nonsaturable accumulation of [6,7-3H]RU 486 from phosphate buffer into adipose tissue was inhibited by the addition of alpha 1-acid glycoprotein, the specific serum transport protein for RU 486, to the buffer medium. Accumulation of [6,7-3H]RU 486 in myometrial specimens was poor. The enterohepatic cycling of RU 486 was assessed in four normal subjects by repetitive intake of charcoal subsequent to ingestion of 200 mg RU 486. Compared to other normal subjects, the serum levels and areas under the concentration curves were lower and t1/2 values shorter in the group given charcoal, suggesting that in vivo RU 486 may be partly pooled in the enterohepatic cycle. Our studies suggest that despite the low volume of distribution and the effective serum binding of RU 486, the myometrial and adipose tissue concentrations of RU 486 and its metabolites were similar (approximately 10(-9)-10(-10) mol/g) after oral intake of RU 486.

Levels of the antiprogestin RU 486 and its metabolites in human blood and follicular fluid following oral administration of a single dose.

Using high-pressure liquid chromatography (HPLC) the antiprogestin RU 486 and two of its metabolites (N-monodemethyl RU 486 and propargyl RU 486) were measured in plasma and follicular fluid of 21 women requesting laparoscopic sterilization. Pretreatment of the women involved ovulation induction with clomiphene and HCG. RU 486 (100 mg) was administered orally and 1 h later blood samples were withdrawn. Thirty-four hours later, at laparoscopy, samples of both blood and follicular fluid were collected. During the 34-h period the average plasma level of RU 486 decreased from 1.93 mumol/l to 0.91 mumol/l, i.e. by -50%. The latter concentration of RU 486 was not significantly different from that found in follicular fluid (0.79 mumol/l). The monodemethyl metabolite exhibited significantly higher plasma levels (3.09 mumol/l) than RU 486 1 h after administration. Thirty-four hours later these levels had decreased to 0.92 mumol/l, i.e. by 70%. In follicular fluid, the levels of the monodemethyl metabolite (1.76 mumol/l) were significantly higher than those of RU 486 (0.79 mumol/l). Because of background noise, only approximate values were established for the propargyl metabolite. These were 0.67 and 0.40 mumol/l, respectively, in plasma and 0.42 mumol/l in follicular fluid. The results indicate that RU 486 and two of its major metabolites can readily cross the blood-follicle barrier of human pre-ovulatory follicles.

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.

Inhibition of folliculogenesis and ovulation by the antiprogesterone RU 486.

Healthy, regularly menstruating women were treated with the antiprogesterone RU 486, Mifepristone (Roussel-Uclaf, Romainville, France) during the follicular phase of the cycle. Three women were given 25 mg of RU 486 on days 1 to 14 of the cycle and five received 25 mg on days 1 to 21 of the cycle. Venous blood samples were collected three times per week during a control cycle and during one treatment cycle in each subject. Serum concentrations of estradiol (E2), progesterone (P), and RU 486 were determined by radioimmunoassays. No drug-related side effects and no spotting or bleeding during RU 486 treatment were observed. Menstrual bleeding was delayed by 8.7 +/- 3.8 days (mean +/- SD) after treatment over days 1 to 14 and by 12.6 +/- 3.2 days after treatment over days 1 to 21. During the treatment with RU 486, the serum concentrations of E2 remained low, indicating effective inhibition of folliculogenesis. After cessation of RU 486 treatment, serum E2 levels rose to similar values as in the control cycle, and subsequently serum P concentrations also reached ovulatory levels in six out of the eight volunteers. The results showed that the antiprogesterone RU 486 delayed folliculogenesis and luteinization even at low doses when given during the follicular phase of the menstrual cycle. It is speculated that this property of RU 486 could be utilized in the design of an estrogen-free combined oral contraceptives.

PIP: The antiprogesterone RU 486 (mifepristone, Roussel-Uclaf, Romainville, France) was taken by 3 women for days 1-14 of the menstrual cycle, and by 5 women on days 1-21, at a low dose of 25 mg/day, to see whether it would affect ovulation. There is normally a brief progesterone peak before the LH surge that precedes ovulation. To monitor the cycle, women reported bleeding symptoms, and their serum estradiol, progesterone and RU 486 levels were assayed. There were no side effects or bleeding or spotting reported. Serum estradiol levels remained below those recorded in the control cycle, indicating that development of the follicle was inhibited. Estradiol levels rose to follicular phase levels after discontinuation of the drug. Menstruation was delayed by 6, 6 and 14 (mean 8.7) days in the women who took RU 486 for 14 days, and by 8, 12, 12, 13 and 18 days (mean 12.6) days in those who took it for 21 days. The subsequent luteal phase was of normal duration and progesterone level. Based on progesterone level, 2 treatment cycles were anovulatory. Serum RU 486 concentrations ranged from 200 to 1400 ng/ml. It is conceivable that an estrogen-free combined oral contraceptive could be developed based on this property of RU 486.