Carbamazepine coadministration with an oral contraceptive: effects on steroid pharmacokinetics, ovulation, and bleeding

Depot medroxyprogesterone acetate concentrations in patients with and without the use of antiseizure medications

OBJECTIVES

To measure plasma concentrations of medroxyprogesterone acetate (MPA) in users with epilepsy treated with antiseizure medications and compare these to MPA concentrations in those without epilepsy.

STUDY DESIGN

For this multisite cross-sectional study, we obtained a single blood sample from those with epilepsy treated with various antiseizure medications (n = 18) within the week before their next depot medroxyprogesterone injection. Among the participants without epilepsy (n = 20), 10 similarly were scheduled within the week prior to the next injection, and 10 were scheduled at earlier intervals to attempt to balance the time intervals between groups. MPA concentrations were determined by a validated assay.

RESULTS

MPA concentrations were similar among those with epilepsy and controls and between groups with and without the use of enzyme-inducing medications. The lowest MPA concentrations, under 0.07 ng/mL, were observed among two of eight using enzyme-inducing antiseizure medications, one of 10 using noninducing medications, and one of 19 controls had concentrations below 0.2 ng/mL.

CONCLUSIONS

In this exploratory study, lower MPA concentrations in some participants using enzyme-inducing antiseizure medications suggest a potential interaction that could reduce depot medroxyprogesterone efficacy.

Physiologically-based pharmacokinetic modeling of prominent oral contraceptive agents and applications in drug-drug interactions

Considerable interest remains across the pharmaceutical industry and regulatory landscape in capabilities to model oral contraceptives (OCs), whether combined (COCs) with ethinyl estradiol (EE) or progestin-only pill. Acceptance of COC drug-drug interaction (DDI) assessment using physiologically-based pharmacokinetic (PBPK) is often limited to the estrogen component (EE), requiring further verification, with extrapolation from EE to progestins discouraged. There is a paucity of published progestin component PBPK models to support the regulatory DDI guidance for industry to evaluate a new chemical entity's (NCE's) DDI potential with COCs. Guidance recommends a clinical interaction study to be considered if an investigational drug is a weak or moderate inducer, or a moderate/strong inhibitor, of CYP3A4. Therefore, availability of validated OC PBPK models within one software platform, will be useful in predicting the DDI potential with NCEs earlier in the clinical development. Thus, this work was focused on developing and validating PBPK models for progestins, DNG, DRSP, LNG, and NET, within Simcyp, and assessing the DDI potential with known CYP3A4 inhibitors (e.g., ketoconazole) and inducers (e.g., rifampicin) with published clinical data. In addition, this work demonstrated confidence in the Simcyp EE model for regulatory and clinical applications by extensive verification in 70+ clinical PK and CYP3A4 interaction studies. The results provide greater capability to prospectively model clinical CYP3A4 DDI with COCs using Simcyp PBPK to interrogate the regulatory decision-tree to contextualize the potential interaction by known perpetrators and NCEs, enabling model-informed decision making, clinical study designs, and delivering potential alternative COC options for women of childbearing potential.

Carbamazepine protects the endometrium against negative effects of estrogen in rats

Carbamazepine (CMZ) increases estrogen metabolism by inducing cytochrome P450 (CYP3A4). We investigated whether CMZ is protective against endometrial hyperplasia (EH). We used 32 female Wistar albino rats divided into four equal groups: the control group received drinking water, the estradiol valerate (EV) group was given EV, the CMZ group was given CMZ, and the EV + CMZ group was given both EV and CMZ. After 30 days the uteri of the rats were removed and serum estrogen and progesterone levels were measured, and endometrial tissue characteristics were evaluated. CYP3A4 expression was assessed using immunohistochemistry. Serum estrogen levels were lowest in the EV group and highest in the CMZ group. Serum progesterone levels were similar among all groups. Glandular density, a proxy measure of EH, was highest in the EV group and lowest in the EV + CMZ group. EH was detected in six of eight rats (75%) in the EV group and two of eight rats (25%) in the EV + CMZ group. Immunohistochemical staining revealed no significant difference in CYP3A4 expression among the four groups. CMZ reduced the negative effect of high dose estrogen that is not balanced by progesterone on the endometrium in rats. The effect likely is probably due to the CYP3A4 enzyme activator effect. CMZ may be protective against EH in high risk women, although confirmation is required.

Drug-Drug Interaction Studies With Oral Contraceptives: Pharmacokinetic/Pharmacodynamic and Study Design Considerations

Oral contraceptives (OCs) are the most widely used form of birth control among women of childbearing potential. Knowledge of potential drug-drug interactions (DDIs) with OCs becomes imperative to provide information on the medication to women of childbearing potential and enable their inclusion in clinical trials, especially if the new molecular entity is a teratogen. Although a number of DDI guidance documents are available, they do not provide recommendations for the design and conduct of OC DDI studies. The evaluation of DDI potential of a new molecular entity and OCs is particularly challenging because of the availability of a wide variety of combinations of hormonal contraceptives, different doses of the ethinyl estradiol, and different metabolic profiles of the progestin component. The aim of this review is to comprehensively discuss factors to be considered such as pharmacokinetics (PK), pharmacodynamics (PD), choice of OC, and study population for the conduct of in vivo OC DDI studies. In this context, metabolic pathways of OCs, the effect of enzyme inhibitors and inducers, the role of sex hormone-binding globulin in the PK of progestins, current evidence on OC DDIs, and the interpretation of PD end points are reviewed. With the emergence of new tools like physiologically based PK modeling, the decision to conduct an in vivo study can be made with much more confidence. This review provides a comprehensive overview of various factors that need to be considered in designing OC DDI studies and recommends PK-based DDI studies with PK end points as adequate measures to establish clinical drug interaction and measurement of PD end points when there is basis for PD interaction.

Consideraciones acerca del reporte y la evaluación del fallo terapéutico en farmacovigilancia

Introducción. Los fallos terapéuticos representan un problema de salud pública. Aunque existe abundante información al respecto, se requiere una revisión crítica de las definiciones existentes.Objetivo. Realizar una revisión crítica del concepto actual de fallo terapéutico, su clasificación y su importancia en farmacovigilancia.Materiales y métodos. Dos revisores independientes realizaron una búsqueda sistemática de las definiciones de fallo terapéutico existentes en la literatura y de los sistemas de clasificación descritos. Con base en esta información, se realizó un análisis crítico y la proposición de una nueva definición consensuada de fallo terapéutico.Resultados. La concepción actual de fallo terapéutico es imperfecta, pues desconoce la disminución del efecto de un medicamento en el uso real en comparación con el periodo de precomercialización, donde la estimación de la eficacia se basa en ensayos clínicos controlados. Aunque la clasificación actual es adecuada, tanto el algoritmo de Vaca-González et al. como las otras herramientas empleadas para evaluar la causalidad en farmacovigilancia dependen de la calidad del reporte.Conclusiones. Es necesario perfeccionar las definiciones actuales de fallo terapéutico y mejorar la calidad del reporte para sacar el máximo provecho de los sistemas de clasificación. Se propone realizar estudios clínicos pragmáticos para los medicamentos comercializados recientemente con el fin de establecer su verdadero perfil de efectividad y seguridad.

The JAK1 Inhibitor Upadacitinib Has No Effect on the Pharmacokinetics of Levonorgestrel and Ethinylestradiol: A Study in Healthy Female Subjects

Upadacitinib is a novel selective oral Janus kinase 1 (JAK) inhibitor being developed for treatment of several inflammatory diseases. Oral contraceptives are anticipated to be a common concomitant medication in the target patient populations. This study was designed to evaluate the effect of multiple doses of upadacitinib on the pharmacokinetics of ethinylestradiol and levonorgestrel in healthy female subjects. This phase I, single‐center, open‐label, 2‐period crossover study evaluated the effect of multiple doses of 30 mg once daily extended‐release upadacitinib on the pharmacokinetics of a single oral dose of ethinylestradiol/levonorgestrel (0.03/0.15 mg; administered alone in period 1 and on day 12 of a 14‐day regimen of upadacitinib in period 2) in 22 healthy female subjects. The ratios (90% confidence intervals) for maximum plasma concentration and area under the plasma drug concentration–time curve from time zero to infinity following administration of ethinylestradiol/levonorgestrel with upadacitinib compared with administration of ethinylestradiol/ levonorgestrel alone were 0.96 (0.89–1.02) and 1.1 (1.04–1.19), respectively, for ethinylestradiol, and 0.96 (0.87–1.06) and 0.96 (0.85–1.07), respectively, for levonorgestrel. The harmonic mean terminal half‐life for ethinylestradiol (7.7 vs 7.0 hours) and levonorgestrel (37.1 vs 33.1 hours) was similar in the presence and absence of upadacitinib. Ethinylestradiol and levonorgestrel were bioequivalent in the presence and absence of upadacitinib. Therefore, upadacitinib can be administered concomitantly with oral contraceptives containing ethinylestradiol or levonorgestrel.

Risk-Benefit Assessment of Ethinylestradiol Using a Physiologically Based Pharmacokinetic Modeling Approach

Current formulations of combined oral contraceptives (COC) containing ethinylestradiol (EE) have ≤35 μg due to increased risks of cardiovascular diseases (CVD) with higher doses of EE. Low‐dose formulations however, have resulted in increased incidences of breakthrough bleeding and contraceptive failure, particularly when coadministered with inducers of cytochrome P450 enzymes (CYP). The developed physiologically based pharmacokinetic model quantitatively predicted the effect of CYP3A4 inhibition and induction on the pharmacokinetics of EE. The predicted C_max and AUC ratios when coadministered with voriconazole, fluconazole, rifampicin, and carbamazepine were within 1.25 of the observed data. Based on published clinical data, an AUC_ss value of 1,000 pg/ml.h was selected as the threshold for breakthrough bleeding. Prospective application of the model in simulations of different doses of EE (20 μg, 35 μg, and 50 μg) identified percentages of the population at risk of breakthrough bleeding alone and with varying degrees of CYP modulation.

Medication management of bipolar disorder during the reproductive years

The management of bipolar disorder during reproductive years is a challenge to both patient and clinician. The rapidly changing landscape of medical literature, newly available medications, and implementation of the Pregnancy and Lactation Labeling Final Rule by the Food and Drug Administration can be dizzying. This article serves as a brief, practical guide on the use of medications for the treatment of bipolar disorder before, during, and immediately after pregnancy. Special focus is devoted to the risk-benefit analysis of using potentially teratogenic medications during pregnancy. Availability and appropriateness of various contraceptive methods and folic acid supplementation in combination with mood stabilizers is also addressed. Every clinician managing bipolar disorder in adult women should be knowledgeable of family planning resources and what to do in the setting of unintended pregnancy.

Contraception for women with epilepsy: counseling, choices, and concerns

Approximately 50% of all pregnancies in women with epilepsy (WWE) occur unplanned. This is worrying, given the increased occurrence of obstetrical complications in WWE, including the risk of seizures and their possible consequences for both the mother and the unborn child. Hormonal contraception is usually regarded as highly effective, but it is subject to numerous bidirectional drug interactions with several antiepileptic drugs. These interactions may lead to loss of seizure control or contraceptive failure. Further concerns are loss of bone mineral density and increased seizure activity due to hormonal effects. Many physicians lack sufficient knowledge regarding these issues, and most WWE have never received adequate counseling. Moreover, several studies show that a large proportion of WWE do not take their medicines regularly. This article reviews all of these issues and offers practical recommendations for the management of contraception in WWE.

Characterisation of the pharmacokinetics of ethinylestradiol and drospirenone in extended-cycle regimens: population pharmacokinetic analysis from a randomised Phase III study

Objectives

The primary objective of this analysis was to characterise the steady-state pharmacokinetics (PK) of ethinylestradiol (EE) and drospirenone (DRSP) in a randomised Phase III study that investigated the contraceptive efficacy and safety of three different regimens of EE 20 µg/DRSP 3 mg.

Methods

Non-linear mixed-effects modelling was used to develop population PK models for EE and DRSP. EE and DRSP serum concentrations were determined in blood samples obtained from approximately 1100 healthy young women on two occasions during the first cycle (Week 3) and after 6 months (Week 27) of EE 20 µg/DRSP 3 mg use. EE 20 µg/DRSP 3 mg was administered as a flexible extended regimen [24–120 days’ active hormonal intake followed by 4 days with no tablet intake (tablet-free interval)], a conventional 28-day cyclic regimen (24 days’ active hormonal intake followed by 4 days of placebo tablets) or a fixed extended regimen (120 days’ uninterrupted active hormonal intake followed by a 4-day tablet-free interval) over 1 year.

Results

The population PK of EE and DRSP in this population were successfully described using the developed population models. All three regimens led to similar steady-state drug exposure during long-term treatment. Only minor changes (≤8%) in the steady-state PK of EE and DRSP were observed between Week 3 and Week 27 of an extended regimen. Body weight (BW) and age had a small, statistically significant impact on the PK of EE and DRSP (BW only) in a covariate analysis, however, these changes were not considered to be clinically relevant.

Conclusions

Extending the established 24/4-day regimen of EE 20 µg/DRSP 3 mg does not change the known steady-state PK of EE and DRSP, suggesting that the clinical efficacy is also similar. This is in line with the published clinical results from this study.

Estimating systemic exposure to ethinyl estradiol from an oral contraceptive

OBJECTIVE

This study was conducted to compare single-dose pharmacokinetics of ethinyl estradiol in an oral contraceptive with steady-state values and to assess whether any simpler measures could provide an adequate proxy of the "gold standard" 24-hour steady-state area under the curve (AUC) value. Identification of a simple, less expensive measure of systemic ethinyl estradiol exposure would be useful for larger studies that are designed to assess the relationship between an individual's ethinyl estradiol exposure and side-effects.

STUDY DESIGN

We collected 13 samples over 24 hours for pharmacokinetic analysis on days 1 and 21 of the first cycle of a monophasic oral contraceptive that contained 30 μg ethinyl estradiol and 150 μg levonorgestrel in 17 nonobese healthy white women. We also conducted an abbreviated single-dose 9-sample pharmacokinetic analysis after a month washout. Ethinyl estradiol was measured by liquid chromatography-tandem mass spectrometry. We compared results of a full 13-sample steady-state pharmacokinetic analysis with results that had been calculated with the use of fewer samples (9 or 5) and after the single doses. We calculated Pearson correlation coefficients to evaluate the relationships between these estimates of systemic ethinyl estradiol exposure.

RESULTS

The AUC, maximum, and 24-hour values were similar after the 2 single oral contraceptive doses (AUC; r=0.92). The steady-state 13-sample 24-hour AUC value was correlated highly with the average 9-sample AUC value after the 2 single doses (r=0.81; P=.0002). This correlation remained the same if the number of single-dose samples was reduced to 4, taken at time 1, 2.5, 4, and 24 hours. The 24-hour value at steady-state was correlated highly with the 24-hour steady-state AUC value (r=0.92; P<.0001). The average of the 24-hour values after the 2 single doses was also correlated quite highly with the steady-state AUC value (r=0.72; P=.0026).

CONCLUSION

Limited blood sampling, including results from 2 single doses, gave highly correlated estimates of an oral contraceptive user's steady-state ethinyl estradiol exposure.

Decreased efficacy of an etonogestrel implant in a woman on antiepileptic medications: a case report

Introduction

Many antiepileptic drugs decrease the efficacy of combined hormonal contraceptives due to their inducing effect on cytochrome P450 liver metabolism. Less is known about the pharmacokinetics and outcomes of concomitant use of the etonogestrel implant and hepatic enzyme-inducing medications.

Case presentation

A 22-year-old Hispanic woman with a long-standing seizure disorder treated with carbamazepine for 9 years became pregnant after 25 months of etonogestrel implant use.

Conclusions

Hepatic enzyme-inducing drugs may reduce the efficacy of contraceptive implants. Contraceptive counseling for patients with medical co-morbidities requiring hepatic enzyme-inducing medications should include this information.

On the proper use of the crossover design in clinical trials: part 18 of a series on evaluation of scientific publications

BACKGROUND

Many clinical trials have a crossover design. Certain considerations that are relevant to the crossover design, but play no role in standard parallel-group trials, must receive adequate attention in trial planning and data analysis for the results to be of scientific value.

METHODS

The authors present the basic statistical methods required for the analysis of crossover trials, referring to standard statistical texts.

RESULTS

In the simplest and most common scenario, a crossover trial involves two treatments which are consecutively administered in each patient recruited in the study. The main purpose served by the design is to provide a basis for separating treatment effects from period effects. This is achieved via computing the treatment effects separately in two sequence groups formed via randomization. The differences between treatment effects can be assessed by means of a standard t-test for independent samples using the intra-individual differences between the outcomes in both periods as the raw data. The existence of carryover effects must be ruled out for this method to be valid. This assumption is usually checked using a pre-test, which is also described in this article. Finally, we briefly discuss the use of nonparametric tests instead of t-tests and more complicated designs with more than two test periods and/or treatments.

CONCLUSION

Crossover trials in which the results are not analyzed separately by sequence group are of limited, if any, scientific value. It is also essential to guard against carryover effects. Whenever ignoring such effects proves unjustified, the treatment effect must be analyzed solely via an analysis of the data obtained during the first trial period. Even the use of this restricted dataset yields results whose validity is not beyond question.