Determining the Exposure Threshold for Levonorgestrel Efficacy Using an Integrated Model Based Meta-Analysis Approach.

Combined oral contraceptive pills are the most commonly used hormonal contraceptives for the prevention of unintended pregnancies in United States. They consist of a progestin (e.g., levonorgestrel (LNG)) and an estrogen component, typically ethinyl estradiol (EE). In addition to adherence issues, drug-drug interactions (DDIs) and obesity (women with body mass index (BMI) ≥ 30 kg/m2 ) are prime suspects for decreased LNG efficacy. Therefore, we developed an integrated physiologically-based pharmacokinetic modeling and model-based meta-analysis approach to determine LNG's efficacy threshold concentrations and to evaluate the impact of DDIs and obesity on the efficacy of LNG-containing hormonal contraceptives (HCs). Based on this approach, co-administration of strong CYP3A4 inducers and LNG-containing HCs (LNG150: LNG 150 µg + EE 30 µg and LNG100: LNG 100 µg + EE 20 µg) resulted in a predicted clinically relevant decrease of LNG plasma exposure (women with BMI < 25 kg/m2 : 50-65%; obese women: 70-75%). Following administration of LNG150 or LNG100 in the presence of a CYP3A4 inducer, there was an increase in mean Pearl Index of 1.2-1.30 and 1.80-2.10, respectively, in women with BMI < 25 kg/m2 (incidence rate ratios (IRRs): 1.7-2.2), whereas it ranged from 1.6-1.80 and 2.40-2.85 in obese women (IRR: 2.2-3.0), respectively. Our results suggest that the use of backup or alternate methods of contraception is not necessarily required for oral LNG + EE formulations except within circumstances of both obesity and strong CYP3A4 inducer concomitance following administration of LNG100.

Preparation and Characterization of an Oral Norethindrone Sustained Release/Controlled Release Nanoparticles Formulation Based on Chitosan.

Norethindrone has short half-life and low bioavailability. The objective was to prepare an oral Sustained Release/Controlled Release (SR/CR) Liquid Medicated Formulation (LMF) to enhance bioavailability and improve patient compliance. Norethindrone was solubilized in HP-ß-CD then complexed with different concentrations of Low Molecular Weight Chitosan (LMWC) (mucoadhesive). PolyElectrolyte Complexes (PECs) were homogenized with oleic acid using different concentrations of tween 80 to form LMFs (nanoemulsions). PECs and LMFs were characterized using different techniques. LMF 2 (optimum formula containing 2.5% w/v LMWC 11 kDa) was administered orally to dogs and mice for pharmacokinetic and adhesion evaluation. DSC, FTIR spectroscopy and SEM images indicated complex formation. Mean diameters of PECs were 183-425 nm, mean zeta potentials were + 18.6-+ 31 mV, and complexation efficiencies were 18.0-20.6%. Ten to fifteen percent tween was needed to prepare homogenous LMFs. Mean diameter of LMF 2 was 10.5 ± 0.57 nm, mean zeta potential was - 11.07 ± - 0.49 mV, encapsulation efficiency was 95.28 ± 1.75%, and each mL contained 145.5 µg norethindrone. SEM images showed spherical homogeneous oil droplets. All of these parameters were affected by molecular weight and concentration of chitosan. Norethindrone release from LMFs was controlled (zero order) for 96 h. It was little affected by molecular weight and concentration of chitosan but affected by concentration of tween 80. LMF 2 adhered to GIT for 48 h and enhanced the bioavailability. It showed no cytotoxicity after considering dilution in GIT and was stable for 3 months refrigerated. In conclusion an effective SR/CR LMF was prepared.

Plasma concentrations of etonogestrel in women using oral desogestrel before and after Roux-en-Y gastric bypass surgery: a pharmacokinetic study.

OBJECTIVE: To investigate whether Roux-en-Y gastric bypass (RYGB) affects oral desogestrel (etonogestrel) pharmacokinetics. DESIGN: Single centre, open label, phase-2 pharmacokinetic study. SETTING: University hospital of Linköping, Sweden. POPULATION: Fourteen women with planned RYGB surgery were included; nine women aged 18-45 years using 75 micrograms desogestrel completed the study. METHODS: Steady-state etonogestrel pharmacokinetic (PK) parameters were measured on three occasions for each individual (at 8 ± 6 weeks before surgery, and at 12 ± 2 and 52 ± 2 weeks after surgery). Each patient served as her own control. On each occasion, serum samples were collected during a 24-hour period and etonogestrel concentrations were determined with ultra-performance liquid chromatography/tandem mass spectrometry. MAIN OUTCOME MEASURES: Area under the plasma concentration time curve of etonogestrel (AUC0-24 hours ). RESULTS: All women had significant postoperative weight loss. There were no significant differences in AUC0-24 hours , terminal half-lives (t½ ), time to peak serum concentrations (Tmax ), or apparent oral clearances of etonogestrel (CLoral ) before and after gastric bypass surgery on any occasion. Peak serum concentrations (Cmax ) increased after 52 ± 2 weeks compared with preoperative values (0.817 ng/ml versus 0.590 ng/ml, P = 0.024). CONCLUSION: To our knowledge, this is the first study to investigate the effects on desogestrel pharmacokinetics after RYGB. This study did not reveal any clinically significant changes in etonogestrel pharmacokinetics, suggesting that oral desogestrel may be used by women after RYGB surgery. The sample size was limited, however, and therefore the results should be interpreted cautiously. TWEETABLE ABSTRACT: The pharmacokinetics of oral desogestrel does not appear to change after gastric bypass surgery.

Metabolite Identification, Reaction Phenotyping, and Retrospective Drug-Drug Interaction Predictions of 17-Deacetylnorgestimate, the Active Component of the Oral Contraceptive Norgestimate.

Ortho Tri-Cyclen, a two-drug cocktail comprised of ethinylestradiol and norgestimate (13-ethyl-17-acetoxy-18, 19-dinor-17α-pregn-4-en-20yn-3 oxime), is commonly prescribed to avert unwanted pregnancies in women of reproductive age. In vivo, norgestimate undergoes extensive and rapid deacetylation to produce 17-deacetylnorgestimate (NGMN), an active circulating metabolite that likely contributes significantly to norgestimate efficacy. Despite being of primary significance, the metabolism and reaction phenotyping of NGMN have not been previously reported. Hence, detailed biotransformation and reaction phenotyping studies of NGMN with recombinant cytochrome P450 (P450), recombinant uridine 5'-diphospho-glucuronosyltransferases, and human liver microsomes in the presence and absence of selective P450 inhibitors were conducted. It was found that CYP3A4 plays a key role in NGMN metabolism with a fraction metabolized (fm) of 0.57. CYP2B6 and to an even lesser extent CYP2C9 were also observed to catalyze NGMN metabolism. Using this CYP3A4 fm value, the predicted plasma concentration versus time area under the curve (AUC) change in NGMN using a basic/mechanistic static model was found to be within 1.3-fold of the reported NGMN AUC changes for four modulators of CYP3A4. In addition to NGMN, we have also elucidated the biotransformation of norgestrel (NG), a downstream norgestimate and NGMN metabolite, and found that CYP3A4 and UGT1A1 have a major contribution to the elimination of NG with a combined fm value of 1. The data presented in this paper will lead to better understanding and management of NGMN-based drug-drug interactions when norgestimate is coadministered with CYP3A4 modulators.

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.

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.

Pharmacokinetic drug-drug interaction between ethinyl estradiol and gestodene, administered as a transdermal fertility control patch, and two CYP3A4 inhibitors and a CYP3A4 substrate.

Pharmacokinetic (PK) interactions between the cytochrome P450 3A4 (CYP3A4) pathway and transdermally administered ethinyl estradiol (EE) and gestodene (GSD) were investigated. This paper reports the findings of three open-label, intra-individual, one-way crossover, Phase I trials. In two studies, women used a novel contraceptive patch for 3 weeks during two 4-week study periods; in the second period, the CYP3A4 inhibitors erythromycin (Study 1) or ketoconazole (Study 2) were administered concurrently. In a third study, women received single doses of the CYP3A4 model substrate midazolam, alone and after 3 weeks of concurrent patch application. In each period, the EE/GSD patch (delivering low EE and GSD doses resulting in the same systemic exposure as a combined oral contraceptive containing 0.02 mg EE and 0.06 mg GSD) was applied once weekly for 3 weeks, with one patch-free week. Erythromycin, ketoconazole, and midazolam were administered orally. Main outcome measures were area under the curves (AUCs) and maximum plasma concentration (C max) of EE, and total and unbound GSD (Studies 1 and 2). AUC and C max of midazolam (Study 3). Co-administration of CYP3A4 inhibitors did not affect EE metabolism, and had only weak effects on the PK of total and unbound GSD. The patch had no clinically relevant effect on metabolism of the CYP3A4 substrate midazolam.

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.

A simple, rapid and sensitive UFLC-MS/MS method for the quantification of oral contraceptive norgestrel in human plasma and its pharmacokinetic applications.

A simple, rapid and sensitive ultra flow liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) assay for the determination of norgestrel in human plasma was developed using levonorgestrel D6 as an internal standard (IS). Norgestrel and IS were extracted from human plasma via liquid-liquid extraction. Chromatographic separation was achieved on a Zorbax XDB-Phenyl column under isocratic conditions. Detection was done by tandem mass spectrometry, operating in positive ion mode. The protonated precursor to product ion transitions monitored for norgestrel and IS were at m/z 313.30→245.40 and 319.00→251.30 respectively. The method was fully validated as per current regulatory guidelines. Anticoagulant counter ion effect was also assessed with K2EDTA and K3EDTA. The method was validated with a linearity range of 304.356-50 807.337 pg/mL having run time of 2.0 min per sample. The method has shown tremendous reproducibility with intra- and inter-day precision (%CV) less than 11.0% and intra- and inter-day accuracy less than 9.0% of nominal values. The validated method was applied to a pharmacokinetic study in human plasma samples generated after administrating a single oral dose of 0.3 mg norgestrel tablets to healthy female volunteers and has proved to be highly reliable for the analysis of clinical samples.

Effect of protease inhibitors on steady-state pharmacokinetics of oral norethindrone contraception in HIV-infected women.

OBJECTIVE: Pharmacokinetic interactions exist between combined oral contraceptives and protease inhibitors (PI). However, such information is lacking for progestin-only oral contraception. We sought to define the steady-state pharmacokinetic interaction between norethindrone (NET) and PI in HIV-infected women. METHODS AND DESIGN: We conducted an open-label, prospective, nonrandomized trial to characterize the steady-state pharmacokinetics of serum NET in HIV-infected women receiving PI compared with a control group of HIV-infected women receiving other noninteracting drugs. After 21 days of 0.35 mg of NET ingestion once daily, serial serum samples were obtained at 0, 1, 2, 3, 4, 6, 8, 12, 24, 48, and 72 hours. The area under the curve between 0 and 72 hours after ingestion was calculated by trapezoidal approximation. RESULTS: Thirty-five women were enrolled, 2 withdrew. Sixteen women in the PI group and 17 controls completed the study. NET half-life and maximum concentration were not significantly different between the 2 groups. Minimum concentration of NET was significantly higher in the PI group (P = 0.01). The ratio of the geometric mean NET area under the curve in the PI group compared with controls was 1.5 (90% confidence interval: 1.21 to 1.86). NET serum concentrations were significantly higher in HIV-infected women taking a PI compared with controls (P = 0.004). CONCLUSIONS: Coadministration of PI inhibits NET metabolism as shown by higher serum NET area under the curve levels, a surrogate marker for therapeutic contraceptive efficacy. This study supports the increased utilization of progestin-only pills in HIV-infected women receiving certain PI regimens.