Pharmacokinetics of the contraceptive steroids levonorgestrel and gestodene after single and multiple oral administration to women

Clinical pharmacology of progestins

INTRODUCTION

In this paper, we report general pharmacological profile and major biological activities of natural progesterone (P) and progestins. The aim of this article consists of synthesizing the principal aspects of pharmacology and metabolism of P and progestins related to the clinical consequences of their use.

METHODS

We review scientific literature on the topic "Progestins", evaluating the most relevant data from original articles, reviews and meta-analyses.

EVIDENCE SYNTHESIS

Progestins represent a specific class of synthetic analogues of P clinically employed (alone or associated with estrogens) to manage several gynaecological conditions, for instance multiple abortions, luteal phase defect, premenstrual syndrome, abnormal uterine bleeding, endometriosis and menopause (for hormone replacement therapy). Besides their use in the field of contraception, many non-contraceptive benefits of estroprogestins are mostly due to the activities of progestins. Pharmacological characteristics, dosage and individual metabolism could be listed among the principal aspects influencing their clinical effects.

CONCLUSIONS

The choice of each progestin according to its pharmacological profile is crucial for the appropriate management of any gynaecological condition. An aware knowledge of these compounds is fundamental to hone medical practice.

Partial Least Square Model (PLS) as a Tool to Predict the Diffusion of Steroids Across Artificial Membranes

One of the most challenging goals in modern pharmaceutical research is to develop models that can predict drugs’ behavior, particularly permeability in human tissues. Since the permeability is closely related to the molecular properties, numerous characteristics are necessary in order to develop a reliable predictive tool. The present study attempts to decode the permeability by correlating the apparent permeability coefficient (P_app) of 33 steroids with their properties (physicochemical and structural). The P_app of the molecules was determined by in vitro experiments and the results were plotted as Y variable on a Partial Least Squares (PLS) model, while 37 pharmacokinetic and structural properties were used as X descriptors. The developed model was subjected to internal validation and it tends to be robust with good predictive potential (R²Y = 0.902, RMSEE = 0.00265379, Q²Y = 0.722, RMSEP = 0.0077). Based on the results specific properties (logS, logP, logD, PSA and VD_ss) were proved to be more important than others in terms of drugs P_app. The models can be utilized to predict the permeability of a new candidate drug avoiding needless animal experiments, as well as time and material consuming experiments.

Misreporting of contraceptive hormone use in clinical research participants

Objective

Researchers traditionally rely on participant self-report for contraceptive use. We hypothesized that self-reported contraceptive use by clinical research participants may disagree with objectively measured hormonal status.

Study design

We enrolled women in Harare, Zimbabwe, aged 18–34, who by self-report had not used hormonal or intrauterine contraception for >30 days, or depot medroxyprogesterone acetate for >10 months, into a study designed to assess biologic changes with contraceptive initiation and use. Blood samples obtained at enrollment and each follow-up visit (N=1630 from 447 participants) were evaluated by mass spectrometry for exogenous hormones. We individually interviewed a subset of participants (n=20) with discrepant self-reported and measured serum hormones to better understand nondisclosure of contraceptive use.

Results

Discrepant with self-reported nonuse of hormonal contraception, synthetic progestogens were detectable in 120/447 (27%, 95% confidence interval 23%–31%) enrolled women. Measured exogenous hormones consistent with use of contraceptive pills (n=102), injectables (n=20) and implants (n=3) were detected at enrollment, with 7 women likely using >1 contraceptive. In-depth interviews revealed that participants understood the requirement to be hormone free at enrollment (100%). Most (85%) cited partner noncooperation with condoms/withdrawal and/or pregnancy concerns as major reasons for nondisclosed contraceptive use. All interviewed women (100%) cited access to health care as a primary motivation for study participation. Of participants who accurately reported nonuse of hormonal contraception at enrollment, 41/327 (12.5%) had objective evidence of nonstudy progestin use at follow-up that disagreed with self-reported nonuse.

Conclusions

Women joining contraceptive research studies may misrepresent their use of nonstudy contraceptive hormones at baseline and follow-up. Objective measures of hormone use are needed to ensure that study population exposures are accurately categorized.

Implications statement

Among Zimbabwean women participating in a contraceptive research study, 27% had objective evidence of use of nonstudy contraceptives at enrollment that disagreed with self-report. Studies that rely on self-report to identify contraceptive hormone exposure could suffer from significant misclassification.

Lack of a Pharmacokinetic Interaction Between SYM-1219 Granules Containing 2 Grams of Secnidazole and a Combined Oral Contraceptive in a Phase 1, Randomized, Open-Label Study in Healthy Female Volunteers

INTRODUCTION

Bacterial vaginosis (BV) is a serious infection that is the most common vaginal infection in women of childbearing potential. SYM-1219 is a novel, granule formulation containing 2 g of secnidazole that is being developed as a single, oral dose to treat women with BV. Because many of the women diagnosed with BV use hormonal contraception, the effect of SYM-1219 on the pharmacokinetics (PK) of commonly prescribed oral contraceptive drugs, ethinyl estradiol (EE2), and norethindrone (NET) was evaluated.

METHODS

This two-period, randomized, open-label study examined effects in 54 healthy female subjects. During the first period of the study, each subject received EE2 0.035-mg/NET 1-mg tablets. During the second period of the study, subjects were randomized to receive either EE2 0.035-mg/NET 1-mg tablets with concomitant 2-g SYM-1219 or 2-g SYM-1219 followed by EE2 0.035-mg/NET 1-mg tablets 1 day later. The PK of EE2 and NET were analyzed for 24 h following administration.

RESULTS

Coadministration of SYM-1219 and EE2/NET, either on the same day or 1 day apart, had no clinically relevant effects on the bioavailability of EE2 or NET. The combined use of SYM-1219 with EE2/NET was well tolerated. Taken together, these results indicate that contraceptive efficacy should be maintained during coadministration of SYM-1219 and EE2/NET.

CONCLUSION

SYM-1219 is a valuable single-dose treatment option for women with BV that will not interfere with combined oral contraceptive methods.

FUNDING

Symbiomix Therapeutics.

Oral micronized progesterone

This review sought to examine the rationale for selecting an oral micronized progesterone formulation rather than a synthetic progestin for some of the main indications for progestogens. Unopposed estrogen use is associated with a high risk (relative risk, 2.1 to 5.7) of endometrial hyperplasia and adenocarcinoma, and it has been understood for some time that a progestogen must be added for at least 10 to 14 days per month to prevent these effects. However, the most commonly used synthetic progestins, norethisterone and medroxyprogesterone acetate, have been associated with metabolic and vascular side effects (eg, suppression of the vasodilating effect of estrogens) in both experimental and human controlled studies. All comparative studies to date conclude that the side effects of synthetic progestins can be minimized or eliminated through the use of natural progesterone, which is identical to the steroid produced by the corpus luteum. The inconvenience associated with the use of injectable, rectal, or vaginal formulations of natural progesterone can be circumvented by using orally administered micronized progesterone. The bioavailability of micronized progesterone is similar to that of other natural steroids, and interindividual and intraindividual variability of area under the curve is similar to that seen with synthetic progestins. A clear dose-ranging effect has been demonstrated, and long-term protection of the endometrium has been established. Micronized progesterone has been used widely in Europe since 1980 at dosages ranging from 300 mg/d (taken at bedtime) 10 days a month for women wishing regular monthly bleeding to 200 mg 14 days a month or 100 mg 25 days a month for women willing to remain amenorrheic. This therapy is well tolerated, with the only specific side effect being mild and transient drowsiness, an effect minimized by taking the drug at bedtime. The prospective, comparative Postmenopausal Estrogens/Progestin Intervention trial has recommended oral micronized progesterone as the first choice for opposing estrogen therapy in nonhysterectomized postmenopausal women.

Modern oral contraceptives and cardiovascular disease

We reviewed evidence that bears on the cardiovascular safety of combined oral contraceptives containing second- and third-generation progestogens and < 50 micrograms of estrogen. Recent epidemiologic studies indicate that current use of these formulations is associated with a smaller increase in the incidence of venous thromboembolism than earlier formulations. In some studies the increase for third-generation formulations containing desogestrel or gestodene was about 1.5 to 2 times that for second-generation formulations, but there is evidence that differences between users in underlying risk and likelihood of being diagnosed contributed to this result. Recent studies of myocardial infarction suggest a smaller increase in risk associated with modern formulations than with earlier ones; one study suggests a threefold increase for second-generation formulations and no increase for third-generation formulations, but the finding requires confirmation. Recent studies of stroke indicate little or no increase in risk for modern formulations among women without risk factors. We conclude that modern combined oral contraceptives are safer than earlier formulations with respect to cardiovascular disease, which occurs rarely in young women.

Pharmacokinetics of the new progestogens and influence of gestodene and desogestrel on ethinylestradiol metabolism

The purpose of the present report is to summarize the most important pharmacokinetic features of the new progestogens. In addition, the question of whether or not gestodene, in comparison to desogestrel, has an influence on the pharmacokinetics of ethinylestradiol (EE2) will be addressed.

An enzyme immunoassay for serum and urinary levonorgestrel in human and non-human primates

A microtiter plate enzyme immunoassay (EIA) is reported for the measurement of levonorgestrel (LNG) in serum and urine samples of human and non-human primates, and the results are compared to data obtained by radioimmunoassay (RIA). Rabbit polyclonal antibodies were raised against the bovine serum albumin conjugate of the 3-O-carboxymethyl oxime (CMO) derivative of LNG. The enzyme label was produced by the conjugation of horseradish peroxidase to LNG at the 3-position by the same CMO bridge used for the immunogen. The assay requires 2.5 hours to perform using 2.2-azino-di-(3-ethylbenzthiazoline sulfonic acid) diammonium salt as the chromogenic substrate. Serum (100 microliters) is extracted with petroleum ether prior to assay, whereas urine samples (25 microliters) are diluted and measured directly. The sensitivity of the assay is 0.25 pg/well with a 50% displacement of label at 7.5-9.5 pg and a linear response through 250 pg/well. Minimum levels of 8.7 and 10.0 pg/ml can be detected in serum and urine samples, respectively. Changes in serum LNG concentrations were measured in women and non-human primates following LNG implantation or injection. In the non-human primate study, serum LNG concentrations began to rise rapidly following i.m. injection of LNG, with peak levels occurring on days 3 to 5, then decreasing to approximately 25-35% of peak levels for the duration of the study. Circulating concentrations of 1.86 +/- 0.18 ng/ml LNG were reached in women the first week post-insertion of Norplant implants and decreased by 50% at 7-10 days, 75% after 14-21 days, followed by a steady decrease during the next 60-70 days to constant low levels that exhibited a high individual variation. Correlation coefficients of EIA and RIA results were 0.988 for human serum, 0.926 for human urine, and 0.972 for non-human primate serum.

Pharmacokinetics of levonorgestrel and ethinylestradiol in 14 women during three months of treatment with a tri-step combination oral contraceptive: serum protein binding of levonorgestrel and influence of treatment on free and total testosterone levels in the serum

The pharmacokinetics of levonorgestrel (LNG) and ethinylestradiol (EE2) were determined in 14 healthy women (age 18 to 27 years) during a treatment period of three months with a tri-step combination oral contraceptive (Triquilar). Prior to this treatment period, the same women received a single administration of a coated tablet containing 0.125 mg LNG together with 0.03 mg EE2. There was a washout phase of one week between both treatments. Following single dose administration, a mean terminal half-life of 22 h was observed for LNG. The total clearance was 1.0 ml x min-1 x kg-1 and the volume of distribution was 128 l. During a treatment cycle, LNG levels in the serum accumulated by a factor of about four as compared to single dose administration. Steady-state drug levels were reached during the second half of each cycle. As compared to single dose administration, the following changes were observed for LNG at the end of treatment cycles one and three: reduced total (0.5 ml x min-1 x kg-1) and free clearance (50 ml x min-1 x kg-1) and a reduced volume of distribution (52 l). A concomitant increase in the SHBG concentrations by a factor of two as compared to pretreatment values was observed during treatment and appeared to be mainly responsible for the changes in the pharmacokinetics of LNG. Marked changes were also seen for the serum protein binding of LNG. After single dose administration, the free fraction of LNG was 1.4% and the fractions bound to SHBG and albumin were 55.0% and 43.6%, respectively. At the end of cycle one, the free fraction was only 1.0% and the fractions bound to SHBG and albumin were 69.4% and 30.0%, respectively. There was no difference in corresponding pharmacokinetic parameters and in the serum protein binding of LNG at the end of cycles one and three. On the last day of treatment cycles one and three, the AUC(0-4h) values of EE2 were 331.2 and 369.6 pg x ml-1 x h, respectively, which corresponds to an about 11-24% increase as compared to single dose administration, where an AUC(0-4h) value of 298.3 pg x ml-1 x h was found. Total and free testosterone concentrations decreased during treatment cycles one and three by about 41% and 55%, respectively, compared with the corresponding values measured prior to treatment.

Serum distribution of two contraceptive progestins: 3-ketodesogestrel and gestodene

A cross-over study of two oral contraceptive formulations, containing 30 micrograms ethinylestradiol in combination with 150 micrograms desogestrel (Marvelon) or 75 micrograms gestodene (Femovan), has been performed to compare the serum distribution and pharmacokinetics of gestodene and the active metabolite of desogestrel, namely 3-ketodesogestrel. Serum concentrations of both sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) were also measured and were increased more than 3-fold and 2-fold, respectively, on day 21 of the treatment cycle, with no statistically significant difference between treatment groups. In addition, 35 days after ingestion of either oral contraceptive had ceased, the serum SHBG and CBG concentrations were similar to the pretreatment values. During treatment cycles, increased serum SHBG levels were associated with a redistribution of 3-ketodesogestrel and gestodene such that the non-protein-bound (NPB) and albumin-bound fractions were reduced in concert with an increase in the relative proportions bound to SHBG. The proportion of gestodene bound to SHBG was consistently higher than that observed for 3-ketodesogestrel, and this undoubtedly reflects the higher affinity of SHBG for gestodene (Kd = 1.2 nM at 37 degrees C) when compared to 3-ketodesogestrel (Kd = 4.7 nM at 37 degrees C). It also probably accounts, in part, for the much higher total serum levels of gestodene (8.58 nmol/L) when compared to 3-ketodesogestrel (2.37 nmol/L) during the treatment cycles. Consequently, the absolute amounts of NPB, non-SHBG-bound, and SHBG-bound gestodene are significantly higher than those measured for 3-ketodesogestrel. It is concluded that ethinylestradiol-induced increases in serum SHBG levels during treatment with Marvelon or Femovan, influenced the distribution and total amount of 3-ketodesogestrel and gestodene in serum, respectively, and that this, combined with the higher affinity of SHBG for gestodene, results in a greater amount of bioavailable gestodene compared to 3-ketodesogestrel, despite the smaller dose of gestodene administered.

Lansoprazole does not affect the bioavailability of oral contraceptives

The effects of the proton pump inhibitor lansoprazole on the bioavailability of a low-dose oral contraceptive (OC), containing 0.03 mg ethinyloestradiol (EE) and 0.15 mg levonorgestrel (LNG), were investigated. Twenty-four healthy females (aged 19-35 years; weight 60.6 +/- 7.1 kg) participated in a multiple-dose, placebo-controlled, randomized two-way cross-over study. All subjects received the OC over 2 full menstrual cycles from day 1 to day 21 separated by a drug-free interval of 7 days. Lansoprazole (60 mg day-1) or placebo was coadministered for 3 weeks each. Plasma concentrations of EE and LNG were determined by GC-MS. The 90% confidence intervals for ratios of Cmax and AUC after log transformation of both EE and LNG ranged between 91 and 111%, indicating that lansoprazole did not affect the bioavailability of EE and LNG.

Influence of changes in the concentration of sex hormone-binding globulin in human serum on the protein binding of the contraceptive steroids levonorgestrel, 3-keto-desogestrel and gestodene

The serum protein binding of levonorgestrel, gestodene and 3-keto-desogestrel has been determined during several clinical studies with different oral contraceptive formulations and one in vitro study. The results of these studies were combined in order to assess the relation between changes in the concentration of sex hormone-binding globulin (SHBG) and the effect on the free fraction of the progestins as well as on their distribution with respect to the binding proteins albumin and SHBG. Although marked differences in protein binding were seen for the three progestins at low concentrations of SHBG, these differences became less pronounced at high levels of SHBG which were reached during established oral contraceptive therapy. A nonlinear relation could be shown for either the free or the protein-bound fraction of the progestins and the concentration of SHBG in the serum, respectively.

Pharmacokinetics of gestodene and ethinylestradiol in 14 women during three months of treatment with a new tri-step combination oral contraceptive: serum protein binding of gestodene and influence of treatment on free and total testosterone levels in the serum

The pharmacokinetics of gestodene (GEST) and ethinylestradiol (EE2) were determined in 14 healthy women (age 18 to 32 years) during a treatment period of three months with a new tri-step combination oral contraceptive (Milvane). Prior to this treatment period, the same women received a single administration of a coated tablet containing 0.1 mg GEST together with 0.03 mg EE2. There was a wash-out phase of one week between both treatments. Following single dose administration, a mean terminal half-life of 18 h was observed for GEST. The total clearance was 0.9 ml x min-1 x kg-1 and the volume of distribution was 84 l. During a treatment cycle, GEST levels in the serum accumulated by a factor of 8 as compared to single dose administration. Steady-state drug levels were reached during the second half of each cycle. As compared to single dose administration, the following changes were observed for GEST at the end of treatment cycles one and three: prolonged terminal half-life (20 to 22 h), reduced total (0.16 ml x min-1 x kg-1) and free clearance (ca. 27 ml x min-1 x kg-1), reduced volume of distribution (ca. 18 l). A concomitant EE2-induced increase in the SHBG concentrations by a factor of three as compared to pretreatment values was observed during a treatment cycle and appeared to be mainly responsible for the changes in the pharmacokinetics of GEST. Marked changes were also seen for the serum protein binding of GEST. After single dose administration, the free fraction of GEST was 1.3% and the fractions bound to SHBG and albumin were 69.4% and 29.3%, respectively. At the end of cycle one, the free fraction was only 0.6% and the fractions bound to SHBG and albumin were 81.4% and 18.0%, respectively. There was no difference in corresponding pharmacokinetic parameters and in the serum protein binding of GEST at the end of cycles one and three. On the last day of treatment cycles one and three, the AUC(0-4h) values of EE2 were 299.2 and 278.1 pg x ml-1 x h, respectively, which corresponds to an about 30% increase as compared to single dose administration, where an AUC(0-4h) value of 216.1 pg x ml-1 x h was found. Total and free testosterone concentrations decreased during treatment cycles one and three by about 36% and 60%, respectively, compared with the corresponding values measured prior to treatment. The fraction of unbound testosterone thus decreased from 0.5% to 0.3% during treatment.

Pharmacokinetics of levonorgestrel in 12 women who received a single oral dose of 0.15 mg levonorgestrel and, after a washout phase, the same dose during one treatment cycle

The pharmacokinetics of levonorgestrel (LNG) was determined in 12 healthy women (age 21 to 33 years), following single dose administration of 0.15 mg LNG. The same preparation was also administered during one treatment cycle after a washout phase of 1 week. After single dose administration, maximum concentrations of LNG in the serum were 4.3 +/- 1.3 ng/ml. Post maximum drug levels declined biphasically with half-lives of 0.6 +/- 0.2 h and 13.9 +/- 3.2 h, respectively. The clearance was calculated to be 1.5 +/- 0.6 ml x min-1 x kg-1. The free fraction of LNG was 1.1 +/- 0.1% and the fractions bound to SHBG and albumin were 61.8 +/- 6.7% and 37.1 +/- 6.7%, respectively. There was a gradual decrease in serum trough levels of LNG from about 0.5 to 0.3 ng/ml during the cycle, and a concomitant decrease in SHBG concentrations in the serum by about 50%. Serum protein binding of LNG changed markedly during the treatment cycle. The free fraction increased to a value of 1.7 +/- 0.3%, the SHBG-bound fraction decreased to 42.0 +/- 11.4% and the albumin-bound fraction increased to 56.4 +/- 11.2%. Total serum clearance increased during the same time period from a mean value of 1.5 to about 2.5 ml x min-1 x kg-1. The clearance of unbound LNG, however, remained unchanged. An examination of the free LNG concentrations revealed the same time course of LNG trough levels during the cycle as the simulated curve. This was derived from the pharmacokinetic parameters which were obtained after single dose administration. Thus, the present study showed that the pharmacokinetics of LNG can be fully explained on the basis of single dose pharmacokinetics and the changes in serum protein binding which were caused by a reduction of SHBG levels in the serum during chronic treatment with LNG.

Pharmacokinetics of levonorgestrel and ethinylestradiol in 9 women who received a low-dose oral contraceptive over a treatment period of 3 months and, after a wash-out phase, a single oral administration of the same contraceptive formulation

The pharmacokinetics of levonorgestrel (LNG) and ethinylestradiol (EE2) were determined in 9 healthy women (age 23 to 42 years), during a treatment period of three months with a low-dose oral contraceptive, containing 0.15 mg LNG together with 0.03 mg EE2 (Microgynon). After a wash-out period of 3 months, 8 of these women received a single administration of the same formulation. The results showed that there was an increase in serum trough levels of LNG, reaching steady-state in the second half of each treatment cycle. The LNG levels achieved were about 3 to 4 times higher than anticipated on the basis of single dose administration. At the end of treatment cycles one and three, the terminal half-life of LNG was in the range of 24-26 h, while a mean value of 20 h was observed following single dose administration. An EE2-induced increase in the SHBG concentration of about 50% as compared to pretreatment values was observed during a treatment cycle. Pretreatment values were reached following the drug-free interval of 7 days between two cycles. After single dose administration, the free fraction of LNG was 1.3 +/- 0.2% and the fractions bound to SHBG and albumin were 64.1 +/- 4.2% and 34.6 +/- 4.0%, respectively. Serum protein binding of LNG did not change during chronic treatment. An about 50% reduction in total and unbound clearance of LNG was observed during chronic treatment, as compared to single dose administration. Increased SHBG binding capacity and a reduced hepatic metabolic capacity were discussed as possible causes of accumulating LNG concentrations in the serum. On the last day of treatment cycles one and three, the AUC(0-24h) values of EE2 were 728 +/- 314 and 778 +/- 318 pg x ml-1 x h, respectively, and were in keeping with data reported from others.

Pharmacokinetics of gestodene in 12 women who received a single oral dose of 0.075 mg gestodene and, after a wash-out phase, the same dose during one treatment cycle

The pharmacokinetics of gestodene (GEST) was determined in 12 healthy women (age 22 to 34 years), following single dose administration of 0.075 mg GEST. The same preparation was also administered during one treatment cycle after a wash-out phase of 1 week. After single dose administration, maximum concentrations of GEST in the serum were 4.9 +/- 2.5 ng/ml. Post maximum drug levels declined biphasically with half-lives of 0.2 +/- 0.2 h and 14.9 +/- 6.7 h, respectively. The apparent clearance was calculated to be 0.8 +/- 0.4 ml x min-1 x kg-1. The free fraction of GEST was 1.3 +/- 0.3% and the fractions bound to SHBG and albumin were 64.3 +/- 10.7% and 34.4 +/- 10.4%, respectively. The results showed that there was a gradual decrease in serum trough levels of GEST during the cycle, due to a concomitant and equally high decrease in SHBG concentrations in the serum of about 26%. At the end of one treatment cycle, the free fraction of GEST increased to 1.8 +/- 0.5%, the SHBG-bound fraction decreased to 57.0 +/- 10.2% and the albumin-bound fraction increased to 41.3 +/- 9.9%. Total serum clearance increased during the same time period from a mean value of 0.8 to about 1.2 ml x min-1 x kg-1. The clearance of unbound GEST, however, remained unchanged. An examination of the free GEST concentrations revealed the same time course of GEST trough levels during the cycle as the simulated curve. This was derived from the pharmacokinetic parameters which were obtained after single dose administration. Thus, the present study showed that the pharmacokinetics of GEST can be fully explained on the basis of single dose pharmacokinetics and the changes in serum protein binding which were caused by a reduction of SHBG levels in the serum during chronic treatment with GEST. There was no evidence of GEST inhibiting its own metabolism.

Single and multiple administration of a new triphasic oral contraceptive to women: pharmacokinetics of ethinyl estradiol and free and total testosterone levels in serum

Ethinyl estradiol is part of almost every combined oral contraceptive, and its pharmacokinetic characteristics have been thoroughly investigated in numerous studies. However, little is known about its pharmacokinetics during long-term administration, as compared with single-dose administration. In this study 10 women received a triphasic formulation that contained ethinyl estradiol together with the progestin gestodene over one treatment cycle. Mean area under the curve values of ethinyl estradiol were significantly higher on the last treatment day, as compared with the corresponding values obtained from the same women after single-dose administration. However, the observed increase in area under the curve was within the range of pharmacokinetic accumulation, to be expected on the basis of dosing interval and terminal half-life. Another point of interest was the effect of the triphasic preparation on testosterone concentrations in serum. Both total and free testosterone levels were suppressed by about 60% as compared with pretreatment values, and there was no correlation with corresponding sex hormone-binding globulin levels in the serum.