Preparation and in vitro/in vivo evaluation of gestodene (GEST) intravaginal ring.

Preparation and in vitro/in vivo evaluation of gestodene (GEST) intravaginal ring (IVR) formulations which can release a constant dose of GEST during 3 weeks were investigated. In present study a reservoir gestodene intravaginal ring, including a gestodene silicone elastomer core and the non-active silicone layer, was reported, which was manufactured by reaction injection moulding at 80°C for 20 min. The raw materials compatibility experiments showed that the silicone elastomer core carrier wouldn't interact with drugs. In vitro release samples were determined by HPLC and the experiment was performed under sink conditions. The equation of cumulative release verse time was Y=64.76χ+5.44 (r=0.9998), performing zero-order release at about the target dose of 60 µg/day over 21 days. Drug release increased with temperature elevating from 45 to 55°C, which could be attributed to optimizing the prescription. In addition, the pharmacokinetic and safety studies of gestodene intravaginal ring were evaluated in female New Zealand White rabbits. The GEST in plasma was analyzed by LC-MS/MS and the results proved that the correlation between in vitro and in vivo was relatively well.

Development and validation of UPLC-MS/MS method for simultaneous determination of gestodene and ethinyl estradiol in rat plasma.

A selective and sensitive ultra-performance liquid chromatography method with tandem mass spectrometric detection for simultaneous determination of gestodene (GES) and ethinyl estradiol (EE) in rat plasma was developed and validated. GES, EE and the internal standard, norgestrel, were extracted with ethyl acetate, derivatized (EE only) with dansyl chloride and then back-extracted into diethyl ether-hexane (2:1, v/v). The separation was performed on an ACQUITY UPLC BEH C(18) column with gradient elution using mobile phase consisting of acetonitrile and water (both containing 0.1% formic acid). The detection was carried out by means of electrospray ionization (ESI) mass spectrometry in positive ion mode with multiple-reaction monitoring. Calibration curves of GES and EE were linear (r(2) >or= 0.99) over the concentration ranges 1.59-159 and 0.196-78.4 ng/mL, respectively. The intra- and inter-day precisions were not more than 6.9 and 12.9% for GES and 10.6 and 9.0% for EE, and the accuracies were -2.5-8.0% for GES, and -7.2-0.19% for EE, respectively. The method herein described was superior to previous methods and was applicable to the pharmacokinetic study of GES and EE in rats.

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.

Pharmacokinetics of single-dose levonorgestrel in adolescents.

PURPOSE: The purpose of this study is to compare the pharmacokinetics of levonorgestrel, a drug used for emergency contraception between female adolescents and adults. METHODS: Twenty-two female subjects, aged 13-16 years, received a single 0.75-mg dose of the drug. Serial blood samples were collected for 72 h and used to measure plasma levonorgestrel concentrations. Previously published data from 16 adults, aged 18-45 years, served as comparison. RESULTS: There was a statistically significant higher total plasma clearance divided by the bioavailability (CL/F) of levonorgestrel in adolescents compared to adults, resulting in lower maximum and average total plasma concentrations. There was a trend for a larger volume of distribution divided by bioavailability (V/F), but there was no significant difference in the half-life of levonorgestrel in adolescents relative to adults (p=.098). CONCLUSION: The differences between adolescents and adults are unlikely to be clinically significant because specific changes in total concentrations suggest that unbound concentrations are probably not affected. Furthermore, empirically high doses of levonorgestrel are given for emergency contraception.

Impact of obesity on the pharmacokinetics of levonorgestrel-based emergency contraception: single and double dosing.

OBJECTIVE: To determine if differences exist in the pharmacokinetics (PK) of levonorgestrel-based emergency contraception (LNG-EC) in obese and normal body mass index (BMI) users and test whether doubling the dose of LNG-EC in obese women increases total and free (active) LNG serum concentrations. STUDY DESIGN: Healthy, reproductive-age women with obese and normal BMIs received 1.5mg LNG orally (ECx1) and then in a subsequent menstrual cycle, the obese group also received 3mg LNG (ECx2). Dosing occurred during the follicular phase. Total and free LNG PK parameters were obtained via serum samples through an indwelling catheter at 0, 0.5, 1, 1.5, 2, and 2.5h. The primary outcome was the difference in total and free LNG concentration maximum (Cmax) between ECx1 and ECx2 in the obese group. RESULTS: A total of 10 women enrolled and completed the study (normal BMI=5, median 22.8kg/m(2), range 20.8-23.7; obese BMI=5, 39.5kg/m(2), range 35.9-46.7). The total LNG Cmax for obese subjects following ECx1 (5.57±2.48ng/mL) was significantly lower than the level observed in normal BMI women (10.30±2.47, p=.027). Notably, ECx2 increased the Cmax significantly (10.52±2.76, p=.002); approximating the level in normal BMI subjects receiving ECx1. Free LNG Cmax followed a similar pattern. CONCLUSION: Obesity adversely impacts both the total and free Cmax levels of LNG EC and this likely explains its lack of efficacy in obese women. Doubling the dose appears to correct the obesity-related PK changes but additional research is needed to determine if this also improves EC effectiveness in obese women. IMPLICATIONS: This study demonstrates that obesity interferes with the pharmacokinetics of LNG EC, and that doubling the dose may be an effective strategy to improve its efficacy in obese women.

Histological characteristics and altered expression of interleukins (IL) IL-13 and IL-15 in endometria of levonorgestrel users with different uterine bleeding patterns.

OBJECTIVE: To determine the relationship between uterine bleeding patterns in levonorgestrel users with endometrial histology and expression of interleukins (IL) IL-13 and IL-15. DESIGN: Prospective observational study. SETTING: Academic research center. PATIENT(S): Questionnaires were sent to patients (n = 578) who had levonorgestrel implants concerning bleeding patterns; 35 of these patients were identified to have regular cycle (n = 13), amenorrhea (n = 8), or metrorrhagia (n = 14). INTERVENTION(S): Endometrial biopsies, serum, histology, and immunostaining. MAIN OUTCOME MEASURE(S): Endometrial histological assessment and immunostaining for IL-13 and IL-15 and for blood levonorgestrel, E2, and progesterone levels by ELISA or RIA. RESULT(S): No correlation was found between circulating levonorgestrel, E2, or progesterone levels with the bleeding patterns, although a trend toward a lower E2 level was observed in patients with amenorrhea who had inactive endometrium. There was a direct correlation between bleeding patterns and endometrial histology, as well as IL-13 and IL-15 expression in patients with regular cycles and metrorrhagia, demonstrating secretory and proliferative endometrium, respectively. Some patients in each group were also identified as demonstrating endometritis. CONCLUSION(S): Endometrial histology may assist directing therapy and subsequently increasing compliance in progestin-only contraceptive users with irregular bleeding who fail to respond to standard therapies. Altered endometrial expression of IL-13 and IL-15, key cytokines in inflammatory and immune cell trafficking, may influence events, leading to irregular bleeding.

Increased exposure of norethindrone in HIV+ women treated with ritonavir-boosted atazanavir therapy.

OBJECTIVE: Pharmacokinetics of norethindrone in combination oral contraceptive regimen are well described among HIV+ women treated with ritonavir-boosted protease inhibitor therapies; however, such characterization is lacking in women using progestin-only contraception. Our objective is to characterize pharmacokinetics of norethindrone in HIV+ women using ritonavir-boosted atazanavir treatment during progestin-only contraceptive regimens. STUDY DESIGN: An open-label, prospective, nonrandomized trial to characterize the pharmacokinetics of norethindrone in HIV+ women receiving ritonavir-boosted atazanavir (n=10; treatment group) and other antiretroviral therapy known to not alter norethindrone levels (n=17; control group) was conducted. Following informed consent, women were instructed to take a single daily fixed oral dose of 0.35 mg norethindrone and 300 mg/100 mg atazanavir/ritonavir for 22 days. On day 22, serial blood samples were collected by venous catheter at 0, 1, 2, 3, 4, 6, 8, 12, 24, 48 and 72 h. Whole blood was processed to collect serum and stored at -20°C until later analysis using radioimmunoassay. Pharmacokinetic parameters were estimated using noncompartmental method. RESULTS: In the treatment group, compared to the control group, an increase in area under the curve0₋24 (16.69 h*ng/mL vs. 25.20 h*ng/mL; p<.05) and maximum serum concentration (2.09 ng/mL vs. 3.19 ng/mL; p<.05), decrease (25%-40%) in apparent volume of distribution and apparent clearance, and unaltered half-life were observed. CONCLUSION(S): Our findings suggest that progestin-only contraceptives, unlike combination oral contraceptives, benefit from drug-drug interaction and achieve higher levels of exposure. Further studies are needed to establish whether pharmacokinetic interaction leads to favorable clinical outcomes. IMPLICATIONS: Norethindrone-based progestin-only contraceptives, unlike combination oral contraceptives, exhibit greater drug exposure when co-administered with ritonavir-boosted atazanavir regimen and thus may not warrant a category 3 designation by the World Health Organization. Prospective studies are needed to confirm whether pharmacokinetic interaction results in favorable clinical outcomes.

Thalidomide does not alter the pharmacokinetics of ethinyl estradiol and norethindrone.

OBJECTIVE: To evaluate the effect of thalidomide on the plasma pharmacokinetics of ethinyl estradiol (INN, ethinylestradiol) and norethindrone (INN, norethisterone). METHODS: Ten women who had undergone surgical sterilization were enrolled in an open-label crossover study conducted in the Georgetown University Clinical Research Center. The pharmacokinetics of single doses of 0.07 mg ethinyl estradiol and 2 mg norethindrone were measured at baseline and after 3 weeks of 200 mg thalidomide. Compliance with the thalidomide regimen was assessed with use of Medication Event Monitoring System (MEMS) caps. RESULTS: No changes were observed in the pharmacokinetics of ethinyl estradiol or norethindrone with thalidomide therapy. The mean +/- SD area under the plasma concentration-time curve (AUC0-infinity) for ethinyl estradiol was 6580 +/- 1100 ng.h/L at baseline and 5970 +/- 1560 ng.h/L after the thalidomide regimen (paired t test, P > .05). The values for norethindrone were 103 +/- 54 micrograms.h/L and 107 +/- 58 micrograms.h/L (paired t test, P > .05). No changes were observed for other pharmacokinetic parameters assessed for either ethinyl estradiol or norethindrone. No accumulation of thalidomide was seen after 21 days of therapy: day 1 AUC0-infinity 41.1 +/- 13.9 micrograms.h/mL; day 21 AUC0-infinity 59.6 +/- 27.3 micrograms.h/mL (paired t test, P > .05). No changes were observed for other pharmacokinetic parameters assessed for thalidomide between days 1 and 21. Thalidomide was well tolerated but caused variable degrees of sedation. The average thalidomide compliance rate was 97%. CONCLUSIONS: The pharmacokinetics of thalidomide do not change with 3 weeks of daily dosing. Thalidomide does not alter the pharmacokinetics of ethinyl estradiol or norethindrone. Therefore there is no drug interaction between thalidomide and these 2 drugs. The efficacy of oral contraceptives containing ethinyl estradiol and norethindrone should not be affected by concomitant thalidomide therapy.

PIP: An open-label crossover study was conducted to evaluate the effect of thalidomide on the plasma pharmacokinetics of ethinyl estradiol (INN, ethinyl estradiol) and norethindrone (INN, norethisterone) among 10 women who had undergone surgical sterilization at Georgetown University Clinical Research Center. The pharmacokinetics of single doses of 0.07 mg ethinyl estradiol and 2 mg norethindrone were measured at baseline and after 3 weeks of 200 mg thalidomide. Compliance with the thalidomide regimen was assessed with the use of Medication Event Monitoring System caps. The results showed that there were no changes in the pharmacokinetics of ethinyl estradiol or norethindrone with thalidomide therapy. Furthermore, no changes were seen for other pharmacokinetic parameters assessed for thalidomide between days 1 and 21. Thalidomide was well tolerated, but caused variable degrees of sedation. The average compliance rate of thalidomide was 97%. This study concluded that there was no drug interaction between thalidomide and the other two drugs (ethinyl estradiol and norethindrone). The efficacy of oral contraceptives containing ethinyl estradiol and norethindrone should not be affected by concomitant thalidomide therapy.

Effect of zonisamide on the pharmacokinetics and pharmacodynamics of a combination ethinyl estradiol-norethindrone oral contraceptive in healthy women.

BACKGROUND: Several antiepileptic drugs have clinically significant pharmacokinetic interactions with oral contraceptives (OCs) that may result in contraceptive failure. OBJECTIVE: The aim of this study was to assess the effect of zonisamide on the pharmacokinetics of the individual components of a combination OC (ethinyl estradiol [EE] 0.035 mg and norethindrone [NOR] 1 mg) and on pharmacodynamic variables that may be increased in the event of reduced contraceptive efficacy (concentrations of serum luteinizing hormone [LH], follicle-stimulating hormone [FSH], and progesterone). METHODS: This was a single-center, open-label, 1-sequence, crossover study. Healthy, premenopausal women received the combination OC for three 28-day cycles (combination OC for 21 days, followed by placebo for 7 days). Following stabilization on the OC during the first cycle, blood was collected during cycle 2 for the determination of serum EE and NOR profiles (day 14) and serum LH, FSH, and progesterone concentrations (days 13-15). Starting on day 15 of cycle 2, zonisamide was administered orally at 100 mg/d and titrated to a target dose of 400 mg/d. EE and NOR profiles and serum LH, FSH, and progesterone concentrations were obtained again in cycle 3 (in the presence of zonisamide) and compared with those from cycle 2 (in the absence of zonisamide). RESULTS: Thirty-seven healthy premenopausal women (mean age, 26.1 years [range, 18-51 years]; mean body weight, 65.5 kg [range, 50.4-93.1 kg]; mean height, 165.8 cm [range, 152.4-182.9 cm]) received > or =1 dose of zonisamide. Of the 33 subjects (89.2%) who completed the study, 26 (78.8%) underwent titration to a stable zonisamide dose of 400 mg/d. For EE, the mean (SD) AUC over a 24-hour dosing interval (AUC(tau)) was 1139 (317) pg.h/mL in cycle 2 and 1143 (312) pg.h/mL in cycle 3; the mean C(max) in the respective cycles was 133 (39) and 141 (46) pg/mL. For NOR, the corresponding values were 140 (48) and 159 (46) ng.h/mL for AUC(tau) and 21 (5.4) and 23 (6.7) ng/mL for C(max). The 90% Cls for the geometric mean ratios (cycle 3:cycle 2) for AUC(tau) and C(max) fell within the accepted range for lack of interaction (0.80-1.25). There were no increases in LH, FSH, or progesterone concentrations between cycle 2 and cycle 3. CONCLUSIONS: In these healthy volunteers, steady-state zonisamide dosing had no clinically significant effect on the pharmacokinetics of EE or NOR. There was no pharmacodynamic evidence that zonisamide is likely to reduce the contraceptive effectiveness of OCs containing EE and NOR.

Contraceptive efficacy, pharmacokinetics, and safety of Annuelle biodegradable norethindrone pellet implants.

OBJECTIVE: To evaluate the contraceptive efficacy, pharmacokinetics, and safety of two formulations of Annuelle (Endocon, Inc., South Walpole, MA) biodegradable norethindrone (NET) SC pellet implants. DESIGN: Prospective observational study. SETTING: Two clinical sites in the United States. PATIENT(S): Thirty-nine healthy, fertile, sexually active women. INTERVENTION(S): Nineteen women received a four-pellet system containing 174 mg NET; 20 women received a five-pellet system containing 266.5 mg NET. MAIN OUTCOME MEASURE(S): Contraceptive efficacy, median serum NET levels, adverse events. RESULT(S): No pregnancies were observed in 293 woman-months in the four-pellet group or in 375 woman-months in the five-pellet group. An initial burst in median serum NET levels occurred in the first 24 hours postinsertion followed by a steady decline over the next 3 years. Norethindrone levels varied considerably among women. The main side effect was bleeding abnormalities, which persisted in half the participants for up to 2 years. No serious adverse events were reported that were related to the pellets. Pellet insertion and removal generally were uncomplicated. CONCLUSION(S): Annuelle shows potential as an effective, safe contraceptive with distinct advantages over other long-acting agents, because it is biodegradable but can be removed if problems arise or if fertility is desired.

PIP: The contraceptive efficacy, pharmacokinetics, bleeding profiles, and safety of two formulations of the Annuelle contraceptive implant system were investigated in a prospective study conducted at two clinical sites in the US. 19 women received a four-pellet system containing 174 mg of norethindrone (NET) and 20 women received a five-pellet system containing 266.5 mg of NET. Participants were followed quarterly for up to 39 months. No pregnancies were recorded during 293 woman-months in the four-pellet group and 375 woman-months in the five-pellet group. Most women exhibited a burst in NET levels (values equal to or exceeding 2 ng/ml) 24 hours after pellet insertion, followed by a steady decline over the next 3 years. Ovulation was inhibited in most participants in both groups at 9 months after insertion, and this protective effect persisted as long as 2 years in 16 of the 39 subjects. More than 80% of women in both groups had at least one clinically important bleeding pattern (e.g., frequent, irregular, or prolonged bleeding) in the first 90-day interval; this percentage dropped over time, but persisted in half the participants for up to 2 years. Serum levels of total cholesterol, low density lipoproteins, and triglycerides dropped substantially after pellet insertion in both groups, while high density lipoprotein levels remained fairly constant. Overall, the Annuelle system is considered to have potential as a safe, long-acting contraceptive agent capable of being surgically removed before complete absorption. Of concern, however, is the relatively long period during which the product releases detectable amounts of NET but may no longer be a fully effective contraceptive agent.

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.

Development of a new sensitive and specific time-resolved fluoroimmunoassay (TR-FIA) of chlormadinone acetate in the serum of treated menopausal women.

We describe the development of a serum chlormadinone acetate (CMA) time-resolved fluoroimmunoassay (TR-FIA). We prepared haptens (3-CMO-chlormadinone acetate and 6-chloropregna-4,6-dien-17,20-diol-3-one-20-hemisuccinate), biotinylated tracers (3(biotinylaminopropylamido) 3-CMO-chlormadinone acetate and 3-(6-chloropregna-4,6-dien-17,20-diol-3-one-20-hemisuccinylamino)1-biotinylaminopropane), and immunogens necessary for eliciting two antibodies (anti-chlormadinone acetate 3-CMO/BSA and anti-chlormadinone 20-hemisuccinate/BSA). The specificity of the assay was rigorously studied to eliminate possible interference by polar metabolites of CMA, particularly 17 alpha-acetoxy-6-chloro-3beta-hydroxypregna-4,6-diene-20-one (3beta-hydroxy metabolite), employing an easy-to-use ethylene glycol chromatographic step prior to immunoassay, so as to separate the polar metabolites, in particular the 3beta-hydroxy-CMA metabolite, from the intact CMA. The choice of the anti-CMA antibody was guided by the high assay sensitivity obtained with the anti-CMA 3-CMO/BSA antibody. The detection limit was 51pg/ml. Interassay reproducibility CVs were between 2.6 and 4.5%. This TR-FIA thus appeared to be a sensitive, specific, precise, and consequently well-suited method for measurement of serum CMA during a pharmacokinetic study in women.

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.

Levels of contraceptive seroids in breast milk and plasma of lactating women.

PIP: Levels of contraceptive steroids in breast milk and plasma of lactating women were investigated. 7 lactating women received 150 mg medroxyprogesterone acetate (MPA) 1 week after delivery. 5 women (lactating) took 350 mcg norethisterone (NET) and 2 took 150 mcg d-norgestrel (d-ng) + 30 mcg ethinyl estradiol. Milk and blood samples were drawn and radioimmunoassay of the contraceptive drug levels were performed. In all 7 women taking MPA, drug was detected in the breast milk and plasma in a ratio of 1:1 for a period of 87 days. NET was also present in milk and plasma but the concentration in milk was about 1/10 of the amount in plasma. d-Ng levels were also less than 1/10 that in plasma.^ieng

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.

PIP: At the outpatient clinic of Lohja District Hospital in Lohja, Finland, clinical researchers examined the pharmacokinetics of mifepristone in 5 healthy women, 29-37 years old, receiving a single dose of 2 mg mifepristone and of 25 mg mifepristone and in 2 other women receiving 8 mg mifepristone each day for 30 days. Regardless of the dose, serum concentrations of mifepristone peaked within 1.2-1.4 hours. These concentrations were proportional to the oral doses: 104-227 ng/ml after 2 mg dose; 474-561 ng/ml after 8 mg dose; and 1285-4851 ng/ml after 25 mg dose. The areas under the concentration curves (0-24 hours) were also proportional to the oral doses: 1134.4, 4846, and 17,015.2, respectively. Daily doses of 8 mg mifepristone over 30 days did not effect cumulative increases in serum concentrations. The women taking the 2 mg and 25 mg single oral doses exhibited different half-lives (24.2 [3 women] vs. 44.4 [2 women] hours; p = 0.001), suggesting that they varied in their ability to metabolize mifepristone. These findings show that, at daily ingestion of 2-25 mg mifepristone, the pharmacokinetics of mifepristone are linear. Based on these findings, the authors think that inhibition of ovulation might be achieved at serum concentrations of about 100 ng/ml.

A radioimmunoassay for norethindrone (NET): measurement of serum NET concentrations following ingestion of NET-containing oral contraceptive steroids.

A sensitive and reliable radioimmunoassay (RIA) for the measurement of norethindrone (NET) in serum has been established employing anti-11 alpha-hydroxynorethindrone 11-hemisuccinyl-bovine serum albumin serum in conjunction with norethindrone-3-(0-carboxymethyl) oximino-[125I]-iodohistamine. Of a number of ring A reduced NET metabolites, only 17 beta-hydroxy-17 alpha-ethinyl-5 beta-estran-3-one (43%) and 17 alpha-ethinyl-5 alpha-estrane-3 beta, 17 beta-diol (15.7%) cross-reacted appreciably in this RIA. Ethinyl estradiol (EE2) and mestranol (MEE2) exhibited cross-reactions of only 1.1 and 0.4%, respectively. Serum NET levels were measured in four groups of 3 women, each ingesting either 1 mg NET plus 0.05 mg MEE2 (Norinyl 1 + 50 or Ortho Novum 1/50), 0.5 mg NET plus 0.035 mg EE2 (Brevicon) or only 0.35 mg NET (Micronor) daily for 5 consecutive days. Peak serum NET levels were observed within 1/2 to 4 hours after oral intake and fell precipitously thereafter. After reaching a maximum, serum NET concentrations declined in a manner consistent with at least two disposition phases. The average half-life for the first disposition phase was 2.3, 3.4, 3.9 and 4.4 hours in subjects ingesting Norinyl 1 + 50, Ortho Novum 1/50, Brevicon and Micronor, respectively. Peak and 3-hour post-ingestion serum NET concentrations were dose-related but showed considerable subject-to-subject variations. Following discontinuation of tablet intake, serum NET levels remained detectable (greater than 0.05 ng/ml) for at least 5 days in all 3 women who had taken Ortho Novum 1/50, but in none of the other 9 volunteers. These results suggest that different preparations of identical doses and combinations of oral contraceptive steroids may yield different serum NET profiles. However, due to considerable subject-to-subject variations, larger numbers of subjects are required for a conclusive investigation.

PIP: A sensitive and reliable radioimmunoassay (RIA) for measuring norethindrone (NET) in serum is described. Of a number of ring-A-reduced NET metabolites, only 2 cross-reacted appreciably in this RIA. Ethinyl estradiol and mestranol exhibited cross-reactions of only 1.1 and .4%, respectively. Serum concentrations of NET before and after ingestion of 4 NET-containing oral contraceptives (OCs) by 3 women each were measured by this RIA. In all 12 volunteers, serum NET levels rose rapidly after oral intake, reaching peak levels within .5-4 hours (median, 1.5) and fell precipitiously thereafter. Peak serum NET averaged 10.2 ng/ml after Ortho Novum 1/50 ingestion, 10.4 after Norinyl 1+50, 7.5 after Brevicon, and 4.3 after Micronor ingestion. Individual peak NET levels varied considerably in each group. Average half-lives varied from 2.3-4.4 hours, depending on OC compound ingested. After discontinuation of OCs, serum NET levels remained detectable ( .05 ng/ml) for at least 5 days in all 3 women who took Ortho Novum 1/50 but in none of the other subjects, suggesting that different preparations of identical doses and combinations of OCs may yield different serum NET profiles.

Plasma protein binding of norethisterone.

Norethisterone (NET) is transported in the blood stream bound to plasma proteins. It is generally believed that only the part of the hormone that is not bound to plasma proteins can exert biological activity. NET binds to albumin and, like other 19-nortestosterone derived progestins, it also binds to sex hormone binding globulin (SHBG). The binding of NET to SHBG was studied in five women during a 21-day treatment cycle with an oral contraceptive containing 3 mg NET-acetate and 50 microgram ethinylestradiol. The total and SHBG-bound concentrations of NET increased in parallel with SHBG during treatment. The fraction not bound to SHBG and the free fraction of NET increased proportionately less, indicating that the total concentrations of NET measured by radioimmunoassay only in part reflect the biologically active fraction of the steroid.

Pharmacokinetics of orally administered norethisterone enanthate in rabbit, monkey, and women.

Norethisterone enanthate (NET-En), an established intramuscular long-acting contraceptive agent, has previously been shown to be effective in inhibiting fertility in two rodent species even 4 days after oral ingestion. Pharmacokinetics of NET and NET-En were studied after oral and intramuscular doses in two animal species and a few women. The results suggest that the NET-En was absorbed within a day in all the species after oral dose. The estimates of relative bioavailability ranged from 13 to 51% in rabbits, monkeys, and women. The elimination half-life was 5-10 days. The presence of the active component, NET, in the circulation over the experimental period of 15 days suggests that NET-En could be useful as a long-acting oral pill. The suppression of progesterone levels during the luteal phase of menstrual cycle in women also supports this finding.

Pharmacokinetics of levonorgestrel 0.75 mg tablets.

This study examined plasma levonorgestrel (LNG) concentrations and pharmacokinetics following oral administration of a single LNG 0.75 mg tablet. Sixteen healthy female volunteers 19-44 years old enrolled in the study. Serial blood samples were drawn over 72 h after dosing in a fasting state. A gas chromatographic, negative ionization mass spectrometric detection analytical method was used to determine plasma LNG concentrations. The observed mean peak plasma LNG concentration was 14.1 +/- 7.9 ng/mL (range 6.7-39.0 ng/mL). The mean time of peak concentration was 1.63 +/- 0.74 h (range 1-4 h). The plasma LNG concentration versus time profiles were subjected to noncompartmental pharmacokinetic analysis for the purposes of determining half-lives, apparent oral clearances (Cl/F), apparent volumes of distribution after oral administration (V/F), and mean residence time (MRT). Half-lives calculated from the terminal decline in plasma LNG concentrations ranged from 16.2 h to 32.3 h (mean = 24.4 +/- 5.3 h). The Cl/F was 7.06 +/- 2.69 L/h, V/F was 260 +/- 129 L, and MRT was 27.8 +/- 5.2 h. LNG was well tolerated; there were no serious adverse events during the study.

Serum distribution of the major metabolites of norgestimate in relation to its pharmacological properties.

Norelgestromin (NGMN) and levonorgestrel (LNG) are the main active metabolites of norgestimate (NGM), but their relative contributions to the pharmacological effects of NGM are unclear. We have therefore determined the serum distribution of these NGM metabolites and assessed their steady-state concentrations in women following >or=3 cycles of oral contraceptive (OC) use. The administration of 250 microg NGM/35 microg ethinyl estradiol (EE) resulted in significantly higher sex hormone-binding globulin (SHBG) levels (p = 0.002), and 30% lower serum non-protein-bound (NPB) levels of testosterone, when compared to treatment with 150 microg LNG/30 microg EE. We also confirmed that NGMN does not bind to SHBG, and found that 97.2% of this metabolite is bound to albumin while only 2.8% is in the NPB fraction. In contrast, most of the LNG was bound to SHBG (92.5% and 87.2% after NGM/EE and LNG/EE treatment, respectively), and the NPB fraction of LNG (0.7%) during NGM/EE treatment was lower (p < 0.001) than during LNG/EE treatment (1.4%). Combining these serum distributions with the C(max) and AUC(0-24h) data obtained after NGM/EE treatment gave NPB and albumin-bound values of NGMN that were much greater than the corresponding LNG values. Furthermore, the C(max) and AUC(0-24h) values for NPB LNG during NGM/EE treatment were estimated to be lower than during LNG/EE treatment. Since LNG is primarily bound by SHBG, its access to target tissues is restricted. Moreover, because SHBG does not bind NGMN, it appears to be quantitatively the more important NGM metabolite available to target tissues, and probably accounts for a substantial proportion of the progestogenic activity of NGM/EE OCs. However, it is also possible that simultaneous exposure of NGMN and LNG after treatment with NGM/EE may provide clinical benefits not seen with LNG/EE combinations.