Comparative study on the efficacy and acceptability of two contraceptive pills administered by the vaginal route: an international multicenter clinical trial.

The efficacy and acceptability of two widely used oral contraceptive tablets, one containing 250 mg levonorgestrel and 50 micrograms ethinyl estradiol and the other containing 150 micrograms desogestrel and 30 micrograms ethinyl estradiol, administered by the vaginal route were compared in 1055 women studied over 12,630 woman-months of vaginal contraceptive pill use. This multicenter clinical trial was performed in nine countries of the developing world by the "South to South Cooperation in Reproductive Health," an organization founded by scientists from the Third World working in the area of reproductive health, and the study was developed and coordinated by one of these centers. The findings of this study confirm the efficacy of both these tablets when administered by the vaginal route. Involuntary pregnancy rates at 1 year of 2.78 for subjects in the levonorgestrel group and 4.54 for subjects the desogestrel group showed no statistically significant difference between the two groups. However, total discontinuation rates of 47.01 for subjects in the levonorgestrel group and 56.33 for subjects in the desogestrel group showed a statistically significant difference between the two groups, and discontinuation rates attributable to prolonged bleeding of 0.6 for subjects in the levonorgestrel group and 3.2 for subjects in the desogestrel group were also significantly higher in the group of subjects using the desogestrel vaginal contraceptive pill. Blood pressure remained at admission values throughout treatment. A statistically significant weight increase from admission values occurred in both groups of subjects.

PIP: Efficacy and acceptability of 2 combined oral contraceptive pills administered vaginally are summarized. This is the 1st collaborative trial published by the South to South Cooperation in Reproductive Health. 1055 women participated in 12,630 cycles, in 9 countries, from June 1988 to May 1991. The pills were commercially available tablets containing 50 mcg ethinyl estradiol and 250 mg levonorgestrel (Schering AG, Sao Paulo, Brazil), or 30 mcg ethinyl estradiol and 15 mcg desogestrel (Organon, Sao Paulo, Brazil). Subjects were aged 17-39 younger and of lower parity from Mexico and Dominican Republic and older from Egypt and China. All had at least 1 pregnancy. 675 participated for 6 months, 470 for 1 year, 364 for 18 months, and 210 for 2 years. The 1-year discontinuation rate averaged 47.01% for the levonorgestrel group and 56.33% for the desogestrel group (p = 0.0061); 2-year discontinuation rates were 48.01% and 69.36, respectively, explained in part by higher involuntary pregnancy rates and prolonged bleeding rates in the desogestrel group. The most common medical reasons for stopping contraception were unplanned pregnancy, vaginal or vulval irritation, nausea, vaginal discharge and headache. Vaginal irritation was reported by 1%, 9 in each group. There were 32 pregnancies, 14 in the levonorgestrel and 18 in the desogestrel group. 17 were in missed pill cycles and the rest were method failures, 6 in the levonorgestrel group and 9 in the desogestrel group. The Pearl index varied from 0 in Nigeria to 12.24 in Mexico, and was 2.45 for levonorgestrel vs. 3.74 for desogestrel. There was a wide variation in discontinuation rates by center: Brazil and China had few, while many women from Dominican Republic, Mexico and Zambia left the study. Bleeding problems were common complaints, more so in the desogestrel group. There were 363 women with intermenstrual bleeding (only once in 80%), 148 with spotting (only twice in 65%). Bleeding duration was significantly less in pill cycles than baseline, pressure. Women gained an average of 1 kg over 2 years, more in the desogestrel group. The pregnancy rate of 2.78 is within the range reported for levonorgestrel rings.

Changes in the responsiveness of prolactin secretion to dopaminergic blockade and TRH stimulation throughout sexual maturation in men.

The pituitary prolactin (PRL) response to domperidone (DOM; a dopaminergic antagonist) and TRH administration in human males during different stages of sexual maturation was investigated. Dopaminergic blockade caused an immediate and significant PRL release in all subjects, regardless of the stage of pubertal development. Even though the mean values of peak PRL levels, magnitude of PRL response (delta PRL) and areas under the PRL curve were not significantly different among the different groups, all these parameters showed a clear tendency to increase in parallel to the stage of pubertal development, as indicated by significant positive correlations between age and pubertal stage of the subjects and the magnitude of their PRL response to DOM (r = 0.661, p less than 0.01 and r = 0.536, p = 0.01, respectively). Significant positive correlations also were found between the serum sex steroid hormone concentrations and the PRL response to dopaminergic blockade (r = 0.774, p = 0.02 and r = 0.554, p = 0.01, respectively). In contrast to these findings, no significant differences or tendencies were detected in the PRL responses to TRH among the different subject groups. The different patterns of PRL response to DOM and TRH throughout male puberty might be due to differences in pituitary thresholds for sex steroids between the dopamine- and TRH-dependent intracellular pools.

Long-acting hormonal contraceptives for women.

Following the development and widespread use of oral hormonal contraceptives, it became evident that alternative long-acting delivery systems would be required to improve contraceptive practice in some cultural settings where injectable or subdermal routes of administration are preferred. Nowadays, long-acting contraceptives constitute an important option in family planning services in many parts of the world. Indeed, two long-acting injectable contraceptives containing just a synthetic progestogen (depot-medroxyprogesterone acetate (DMPA) and norethisterone enantate (NET-EN)) have been in clinical practice for more than 20 years. The World Health Organization's (WHO) Special Programme of Research in Human Reproduction, in collaboration with the U.S. National Institute of Child Health and Human Development (NICHD) and universities primarily in developing countries undertook a synthesis programme aimed at producing an improved injectable preparation by developing new derivatives of known steroids. One such compound (levonorgestrel 17-butanoate) is now at the stage of Phase II clinical testing. In addition, the Special Programme has developed and improved once-a-month injectable formulations and assessed their safety and efficacy in different countries worldwide. After large scale clinical testing, at least two progestogen-estrogen combinations have reached the point of introductory trials.

PIP: A survey of recent trials of new injectable hormonal contraceptives, progestogen-only, levonorgestrel esters, and once monthly injectables, follows a brief review of all the experimental long-acting contraceptive modalities, injectables, implants, vaginal rings, and hormone-releasing IUDs. Currently medroxyprogesterone acetate (DMPA) and norethisterone enanthate (NET-EN) are being used by 7 million women. WHO is conducting dose reduction trials and studies of bioavailability in various national populations. Even though a dose of 100 mg DMPA every 3 months has been satisfactory for contraception, 150 mg is still recommended until further pharmacodynamic data are available. Some populations, notably Thais and Mexican women, have higher peaks and more rapid elimination rates of DMPA, while Chinese women show slower elimination and higher blood levels of NET-EN. Extensive studies of new synthetic esters of levonorgestrel have proceeded to Phase II clinical trials with levonorgestrel butanoate. This ester is an effective contraceptive for 3 months at 12.5 mg, or 5-6 months at a dose of 25 or 50 mg. Trials of combined estrogen and progestogen injectables once-monthly have been ongoing for 10 years. The ratio of the 2 components is as important as the amounts. 2328 women from 12 countries participated in trials of DMPA 25 mg-estradiol cypionate 5 mg, and NET-EN 50 mg-estradiol valerate 5 mg. The continuation rate was better than that for 3-monthly progestogen-only injectables, because of less irregular bleeding. A combined injectable called Cyclofem, DMPA 25 mg-estradiol cypionate is being introduced in several countries. The steadily increasing demand for long-acting injectables prompts development of better formulations.

Comparative effects of short term treatment with norethisterone and sex steroids on gonadotropin secretion in rat pituitary cell cultures.

The short term effects of norethisterone (NET), progesterone (P), estradiol (E2) and dihydrotestosterone (DHT) on the gonadotropin secretion of pituitary cells, from both male and female rats, in primary culture primed with E2 were studied. In female cells, NET only increased the GnRH-induced secretion of LH, while P increased both LH and FSH. Male pituitary cells showed an increased response to GnRH after P pretreatment only if the E2 concentration was augmented. However with the same E2 conditions pretreatment with NET decreased the stimulated LH, but not FSH secretion. Pretreatment with E2 inhibited LH stimulated secretion from pituitary cells of male but not female rats. Furthermore DHT treatment diminished the GnRH response for both LH and FSH in pituitary cells from both sexes. Androgen pretreatment increased basal gonadotropin secretion in male but not in female cells. Basal FSH secretion was increased by NET pretreatment in male cells. This suggests that NET is metabolized by cultured pituitary cells to A-ring reduced compounds during the 4 h incubation period. The formation of NET metabolites, particularly the 3 beta, 5 alpha and 5 alpha-NET might be responsible for the estrogenic and androgenic effects observed when NET was administered to the cultured pituitary cells.

Further studies on the antigonadotropic mechanism of action of norethisterone.

To examine the molecular mechanisms involved in the antigonadotropic effects of norethisterone (NET) and two of its A-ring reduced metabolites the 5 alpha-norethisterone (5 alpha-NET) and the 3 beta, 5 alpha-norethisterone (3 beta, 5 alpha-NET) at the neuroendocrine level, a series of experiments were undertaken in adult castrated rats. Animals were primed either with 0.2 mg of tamoxifen (Tam) for 4 consecutive days or 1.0 mg of cyproterone acetate (CPA) for 7 days followed by a single subcutaneous injection of 0.5 mg of NET, 5 alpha-NET or 3 beta, 5 alpha-NET. Four hours later, they were sacrificed and blood obtained for the measurement of immunoreactive serum LH and FSH. The results indicated that antiestrogen (Tam) pretreatment precluded the inhibitory effects of NET and the 3 beta, 5 alpha-NET but not those of the 5 alpha-NET derivative. Pretreatment with CPA did not modified the antigonadotropic action of the 3 beta, 5 alpha-NET metabolite but it markedly reduced the inhibitory action of the 5 alpha-NET, thus indicating that in the experimental model used, the antigonadotropic effects of NET, are in part the result of its metabolic conversion to its A-ring reduced metabolites. While the 5 alpha-NET displayed an androgenic effect, the 3 beta, 5 alpha-NET exhibited estrogen-like effect at the neuroendocrine level.

Dysfunction of dopaminergic regulation of prolactin in patients with functioning and nonfunctioning pituitary adenomas and craniopharyngiomas.

The response to domperidone (a dopamine blocking agent) of serum prolactin (PRL) levels was compared in 3 patients with amenorrhea-galactorrhea without evidence of a pituitary tumor, 23 patients with prolactinomas (10 cases with histologic confirmation), 7 patients with histologically verified large nonfunctioning pituitary adenomas with normal or moderately elevated basal PRL levels, and 6 patients with histologically verified craniopharyngiomas (3 with normal basal PRL levels and 3 with elevated PRL levels). The response was compared with that of 10 patients with postpartum hyperprolactinemia and 14 normal women. Ten milligrams of intravenous domperidone induced a rapid rise in PRL that was maximal at 30 to 45 minutes in normal, postpartum, and amenorrhea-galactorrhea patients who had no sign of tumor. In contrast, domperidone failed to induce significant changes in PRL in cases of prolactinoma, nonfunctioning pituitary adenomas, and craniopharyngioma with or without elevated basal PRL levels. The results suggest that dopaminergic control on PRL secretion was impaired in all tumor cases. The mechanisms of this abnormal dopaminergic control, however, may be different. Whereas dopamine control in cases of prolactinoma is altered at the level of pituitary dopamine receptors, alternative explanations must be found for those tumors with normal basal PRL levels and lack of response to domperidone.

Ability of an anti-luteinizing hormone-releasing hormone vaccine to inhibit gonadotropins in postmenopausal women.

OBJECTIVE: To determine the effects of immunization with an anti-LH-releasing hormone (LH-RH) vaccine in postmenopausal women. DESIGN: Pilot clinical study. SETTING: Normal human volunteers in a medical research-training environment. PATIENT(S): Three postmenopausal women with a mean age of 60 years, 5 years of amenorrhea, and severe hypoestrogenism with elevated serum LH and FSH. INTERVENTION(S): Intramuscular immunization with 300 micrograms LH-RH equivalent of the vaccine in two occasions 1 month apart. MAIN OUTCOME MEASURE(S): Patients were followed for clinical assessment and serum LH, FSH, and anti-LH-RH titers at regular monthly intervals for 7 months. RESULTS(S): The injection of the anti-LH-RH vaccine followed by a booster injection 1 month later resulted in a sharp decrease, 60 days after the first injection, of both serum gonadotropins, accompanied by an increase in anti-LH-RH antibody titers, which were reversible after 180 days in the absence of further booster immunization. CONCLUSION(S): Active immunization offer a safe option to induce antibody response, which in the present regime employed was of about 6-months duration. This procedure opens new possibilities for its use as an affordable therapeutic agent in some hormone-dependent clinical conditions.

Absorption of dihydrotestosterone (DHT) after its intramuscular administration.

In order to produce a sustained release system for natural androgens, two groups of six hypogonadal males received intramuscular (IM) 40 mg crystalline dihydrotestosterone (DHT), either with particle size of less than 50 microns (DHT-M) or between 100 and 150 microns (DHT-C). Serum DHT was analyzed through 51 days of follow-up. In the DHT-M group, serum DHT was above pretreatment values for 17 days, whereas in the DHT-C group, this period was extended over 50 days. The area under the serum concentration-time curve and the half-life of absorption calculated for the DHT-C group were greater than those obtained for the DHT-M group (55.1 ng/day/ml and 21 days vs. 14.5 ng/day/ml and 6 days; P less than 0.01). The authors conclude that DHT injection appears to be an effective and convenient technique for restoring serum physiologic DHT levels. This approach is suitable for long-term substitution therapy.

Variations in serum lipids and lipoproteins throughout the menstrual cycle.

One hundred fourteen women of reproductive age were included in a cross-sectional study with the aim of establishing the variations in serum lipids and lipoproteins during the menstrual cycle. Total cholesterol, triglycerides, and phospholipids were determined in whole serum and in the following lipoprotein fractions: very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins, obtained by ultracentrifugation. A significant decrease was found in total cholesterol (P less than 0.05) and phospholipids (P less than 0.01) during the late luteal phase. The LDL cholesterol decreased during the luteal phase and VLDL cholesterol increased in the early and midluteal phases. The LDL phospholipids and VLDL triglycerides also showed a significant decrease during the luteal phase (P less than 0.01). The results of this investigation demonstrate major fluctuation in cholesterol, triglyceride, and phospholipid-lipoprotein composition during the menstrual cycle.

Ovarian function following a single administration of depo-medroxyprogesterone acetate (DMPA) at different doses.

The effects of a single administration of depo-medroxyprogesterone acetate (DMPA) at different doses upon ovarian function was studied in a group of healthy ovulating Mexican women. Single doses of DMPA of 25, 50, 100, and 150 mg were intramuscularly administered. Ovarian function was assessed by the measurement of the serum levels of 17 beta-estradiol and progesterone in blood samples drawn twice weekly for 6 months after DMPA administration. The results disclosed that ovulation was inhibited in all cases for at least 3 months following DMPA administration even at the lowest dose, whereas the return of luteal function exhibited a significant positive correlation with the dose of DMPA administered. As expected, follicular activity preceded that of luteal function in all subjects. A correspondence between serum medroxyprogesterone concentrations and ovarian function was found. The overall data indicated that the currently used contraceptive formulation (150 mg) is well above the effective pharmacologic range, and suggested that the dose can be substantially reduced without losing its anovulatory potency.

Solid-phase radioimmunoassay for norethisterone.

Exposure of polystyrene tubes to solutions of glutaraldehyde was shown to provide a stable and consistent surface for immobilising an unpurified norethisterone-specific antiserum. Properties of the solid-phase antiserum were evaluated with respect to its application in developing a solid-phase radioimmunoassay for norethisterone. The assay proved to be sufficiently accurate, precise and sensitive for routine use. The technology is considered to be suited to automation.

A rapid and sensitive radioimmunoassay for norethisterone.

A direct radioimmunoassay for the measurement of norethisterone (NET) in unextracted serum samples was developed. The combined use of a highly specific unpurified antiserum and heat treatment of diluted serum samples obviated both extraction and chromatographic procedures. The direct NET assay fulfilled all the quality control parameters. When this assay was compared with other methods involving either solvent extraction and/or chromatographic purification procedures, no significant differences were observed. The overall results were interpreted as demonstrating that this simple, rapid and reliable NET assay can be used as a helpful tool in metabolic and pharmacokinetic studies of this contraceptive progestogen.

Pharmacokinetics of once-a-month injectable contraceptives.

The addition of a short- or medium-acting estrogen ester to the long-acting progestins depot-medroxyprogesterone acetate (DMPA) and norethisterone enanthate (NET-EN) to produce "combined" injectable formulations has proved a successful strategy in the development of once-a-month injectable contraceptives. Recent clinical pharmacokinetic studies undertaken on once-a-month injectable contraceptives in various WHO Collaborating Centers have guided the selection of the estrogen-progestogen combinations, ratios and dose schedules. At least three combined once-a-month injectable preparations exhibit acceptable pharmacokinetic and pharmacodynamic profiles; however, further improvement in the design of optimal estrogen/progestin injectables are expected during this decade.

PIP: The World Health Organization [WHO] Special Programme of Research, Development and Research Training in Human Reproduction has coordinated the developmental strategy of combined once-a-month injectable contraceptives. The strategy consists of the selection, based on pharmacokinetic data, of appropriate long-acting progestin-estrogen combinations to develop at least 2 sustained-release formulations; assessment of safety and effectiveness of these formulations in clinical research facilities; and their evaluation at field level through service facilities of national family planning programs. WHO Collaborating Centers were involved in selecting the estrogen-progestogen combinations, ratios, and dose schedules. Research has found at least 3 combined once-a-month injectable contraceptives that demonstrate acceptable pharmacokinetic and pharmacodynamic profiles. 2 safe and effective once-a-month contraceptive formulations (Cyclofem and Mesigyna) can join the existing choice of contraceptive methods. WHO expects more improvement in the design of optimal estrogen/progestin injectables in the 1990s.

Review of ovulation return upon discontinuation of once-a-month injectable contraceptives.

Once-a-month combined injectable preparations draw their contraceptive efficacy from continuous ovulation suppression. When their use is discontinued, ovulation resumes within a few weeks or a few months, depending on the formulation. After use of the dihydroxyprogesterone acetophenide 150 mg/estradiol enanthate 5 mg combination for one to two years, ovulation returns in most subjects 3-4 months after discontinuation of treatment. Similarly, recent data show that after 2-year use of the depot-medroxyprogesterone acetate 25 mg/estradiol cypionate 5 mg or the norethisterone enanthate 50 mg/estradiol valerate 5 mg combination, approximately 70% women have resumed ovulation by the third month post-treatment. This is shorter than the time for return of ovulation experienced by ex-users of progestogen-only injectable contraceptives.

PIP: This paper reviews the progress made in the determination of ovulation and specifically addresses the effects of returning ovulation after discontinuance of once-a-month injectable contraceptive preparations. Correlation between ovulation and the hormones estrogen, progesterone, and luteinizing hormone (LH) is well documented. It has served as the basis for many studies on determining ovulation mid-point and in evaluating the efficacy, safety, and time of returned ovulation when using various contraceptive methods and preparations. Current monthly injectable contraceptive formulations are discussed and used as comparison for the new generation injectables. New generation contraceptives in this study are preparations (combinations) of several compounds. The depot microcrystalline form of medroxyprogesterone acetate (DMPA) in combination with estradiol cypionate (E2-Cy) was studied. The authors conclude that these initial studies on the new generation combination monthly injectables indicate that these new contraceptives are highly effective in inhibiting ovulation, as well as allowing for predictable return of ovulation.

A pilot study on the assessment of a progesterone/estradiol sustained release as once-a-month-injectable contraceptive.

A pilot study to assess the use of natural hormones in macrocrystalline sustained release system was undertaken in normal menstruating women. Progesterone at a dose of 100 mg in combination with 5 mg estradiol-17 beta aqueous macrocrystalline suspension (3ml) of defined particle size range (100-250 microns) were administered to five female volunteers of reproductive age, on day 5 of their normal menstrual cycles and then every 28 days consecutively for the next two months. Peripheral venous blood samples were obtained from the women three times a week for 60 days after the third injection for the measurement of serum progesterone, estradiol-17 beta, LH and FSH. The menstrual bleeding patterns were closely monitored during the study period. The results obtained indicate that the exogenous hormone administration produces blood levels similar to those observed during the luteal phase of the menstrual cycle. Follicular maturation as assessed by endogenous estradiol rise, above 150 pg/ml, occurred 29.7 days s.d. 6.4 after the injection. Ovulation as measured by progesterone levels above 5 ng/ml was documented 34.4 days s.d. 4.3 after the third injection. The bleeding patterns were regular though initially shorter but these increased progressively towards normal pattern during course of the study. The data suggest that progesterone/estradiol-17 beta combination administered as an aqueous macrocrystalline suspension is capable of producing sustained ovulation inhibition and could be applied in the design of new once-a-month injectable contraceptives.

Return to ovulation following the use of long-acting injectable contraceptives: a comparative study.

A comparative study was undertaken in twenty-four Mexican women who discontinued the use of depo-medroxyprogesterone acetate (DMPA) or norethisterone enanthate (NET-EN) to assess the time required for the return to menses and ovulation. All subjects were exposed to long-acting injectable contraceptives for at least one year, and were followed prospectively. Serum progesterone levels were determined weekly in all subjects beginning 3 months after the last progestogen injection. Mean time to return to ovulation occurred significantly earlier (p less than 0.001) after NET-EN (2.6 months) as compared with DMPA (5.5 months). No correlation between the return to ovarian function and the duration of steroid exposure was found. The overall data was interpreted as demonstrating a clear-cut difference between the two long-acting progestogens in terms of ovulation suppression.

Predictive value of serum ferritin in anemia development after insertion of T Cu 220 intrauterine device.

A one-year follow-up study in 30 healthy women was undertaken to study serum ferritin as well as other hematological parameters prior, six and twelve months after insertion of an intrauterine device, T Cu 220. Women were allocated into one of two groups according to the baseline ferritin serum levels; Group I abnormal ferritin and Group II normal ferritin levels. Other hematological parameters were normal and no iron supplement was given throughout the study. A direct relationship between low ferritin serum values (Group I), and anemia development was found. Seven out of 15 developed anemia, whereas only 2 out of 15 had anemia at twelve months in Group II with normal ferritin values. The overall data suggested that measurement of serum ferritin levels could be a useful tool to anticipate anemia development in women with intrauterine devices.

PIP: A 1-year follow-up study in 30 healthy women was undertaken to study serum ferritin as well as other hematological parameters prior, 6 and 12 months after insertion of the TCu 220 IUD. Women were allocated to 1 of 2 groups according to the baseline ferritin serum levels; Group 1 abnormal ferritin and Group 2 normal ferritin levels. Other hematological parameters were normal and no iron supplement was given throughout the study. A direct relationship between low ferritin serum levels (Group 1), and anemia development was found. 7 or 15 developed anemia, whereas only 2 of 15 had anemia at 12 months in Group 2 with normal ferritin values. The overall data suggested that measurement of serum ferritin levels could be a useful tool in anticipating anemia development in women with IUDs.

Development of a low-dose monthly injectable contraceptive system: II. Pharmacokinetic and pharmacodynamic studies.

A drug delivery system which provides a sustained release of norethindrone (NET) and mestranol (ME) for one month after a single intramuscular injection was assessed as a long-acting injectable contraceptive. The system is based upon well defined particle size crystals of the synthetic steroids maintained in suspension with saline solution. Eight healthy ovulating women volunteered for the study; they received a combination of 10 mg of NET plus 1 mg of ME in 1 ml of vehicle by intramuscular injection on day five of their menstrual cycle. Blood samples were drawn at 0, 1, 5, 10, 13, 17 and 21 days after drug administration. The immunoreactive serum levels of estradiol, progesterone, NET and ethinylestradiol were measured by specific radioimmunoassay procedures to assess ovarian function and the kinetic parameters of the synthetic steroids. This newly developed contraceptive system proved to be both effective, and long-lasting as well as devoid of side effects.

Assessment of a new low-dose once-a-month injectable contraceptive.

Norethisterone (NET) in combination with mestranol (ME), in a macrocrystalline aqueous suspension that provides sustained release of steroids, was assessed as a once-a-month injectable contraceptive in ten healthy women of reproductive age. The ovarian function was studied before and after the intramuscular administration of 12mg NET plus 1.2mg ME, delivered as crystals of 150 micron average size. Serial blood samples were taken throughout the injection intervals in all women to measure serum progesterone (P), estradiol (E2), and NET. The NET/ME preparation effectively inhibited ovulation in 23 out of the 25 injection intervals studied. The administration of this formulation induced in some women a small degree of follicular maturation not followed by luteal activity. The endometrial bleeding patterns after each injection showed a bleeding-free period of two to three weeks. The overall data demonstrate that the parenteral administration of a macrocrystalline steroid preparation of NET/ME can bring about a sustained release contraceptive system at a substantially lower dose than those currently employed in once-a-month injectable contraception.

Norethisterone-cholesterol eutectic mixture as an oral sustained-release hormonal preparation: bioequivalence study in humans.

A solid dispersion of norethisterone and cholesterol (NET:CHOL; eutectic 1:4 w/w) was prepared by melting and rapid cooling. The fused material was then mixed with lactose as vehicle. Soft gelatin capsules were filled with 55 mg of the final mixture to give 0.35 mg of NET. One control formulation prepared with fused NET and lactose (NET:LAC) was capsuled with the same NET dosage, and one commercial tablet (Dianor, Syntex) with 0.35 mg NET were used as reference formulations. In a cross-over study, five female volunteers received, one month apart, in fasting state, each one of the three formulations. Blood samples were drawn at O,O.5,1,1.5,2,4,8,12,24 and 36 hours after dosing. Immunoreactive plasma NET was measured by RIA to assess pharmacokinetic parameters. The NET:CHOL formulation showed a greater area under the serum concentration-time curve, lower peak concentrations and a smaller release rate constant as compared to the reference preparations. It is concluded that the NET:CHOL eutectic mixture is a modified release dosage form and a sound approach in regulating the drug access rate to the body's central compartment.