Obstetrical, fetal, and lactation pharmacology-a crisis that can no longer be ignored

The dosing regimen for 17-hydroxyprogesterone caproate was suboptimal: lessons for future pharmacotherapy for pregnant women

BACKGROUND

Makena (17-hydroxyprogesterone caproate) was approved by the United States Food and Drug Administration for the prevention of recurrent spontaneous preterm birth in 2011 under the accelerated approval pathway, but fundamental pharmacokinetic or pharmacodynamic (Phase 1 and Phase 2) studies were not performed. At the time, there were no dose-response or concentration-response data. The therapeutic concentration was not known. The lack of such data brings into question the dosing regimen for 17-hydroxyprogesterone caproate and if it was optimized.

OBJECTIVE

The purpose of this study was to evaluate the dosing regimen for 17-hydroxyprogesterone by analyzing 3 data sets in which the 17-hydroxyprogesterone caproate pharmacology was evaluated, namely the Maternal-Fetal Medicine Omega 3 study, the Obstetric-Fetal Pharmacology Research Units study, and the Obstetrical-Fetal Pharmacology Research Centers study. If an inappropriate dosing regimen could be identified, such information could inform future studies of pharmacotherapy in pregnancy.

STUDY DESIGN

Data from the Omega 3 study were used to determine if plasma concentration was related to spontaneous preterm birth risk and if a threshold concentration could be identified. Data from the Obstetric-Fetal Pharmacology Research Units study were used to determine the half-life of 17-hydroxyprogesterone caproate and to develop a model to simulate drug concentrations with various dosing regimens. Data from the Obstetrical-Fetal Pharmacology Research Centers study were used to determine the relationship between dose and safety outcomes.

RESULTS

Analysis of the Omega 3 data set indicated that the risk for spontaneous preterm birth decreased as the log concentration of 17-hydroxyprogesterone caproate increased (odds ratio, 0.04; 95% confidence interval, 0.00-0.90). A steady state concentration of >9 ng/mL (equivalent to >8 ng/mL at 25-28 weeks) was associated with the lowest risk for spontaneous preterm birth (hazard ratio, 0.52; 95% confidence interval, 0.27-0.98; P=.04); this concentration was not achieved in 25% of subjects who received the 250 mg weekly dose. In the Obstetrical-Fetal Pharmacology Research Units study, the adjusted half-life (median and interquartile range) of 17-hydroxyprogesterone caproate was 14.0 (11.5-17.2) days. Simulations indicated that with the 250 mg weekly dose, >5 weekly injections were required to reach the 9 ng/mL target; however, those with the shortest half-life (corresponding to higher clearance), never reached the targeted 9 ng/mL concentration. In 75% of subjects, a loading dose of 500 mg weekly for 2 weeks followed by 250 mg weekly achieved and maintained the 9 ng/mL concentration within 2 weeks but in those 25% with the shortest half-life, concentrations exceeded the 9 ng/mL target for only 3 weeks. In the Obstetrical-Fetal Pharmacology Research Centers study, all 65 subjects who received a weekly dose of 500 mg exceeded the 9 ng/mL steady state.

CONCLUSION

The dosing regimen for 17-hydroxyprogesterone caproate was inadequate. There is a significant inverse relationship between drug concentration and spontaneous preterm birth. The risk was lowest when the concentration exceeded 9 ng/mL, but 25% of women who received the 250 mg weekly dose never reached or maintained this concentration. The drug's long half-life necessitates a loading dose to achieve therapeutic concentrations rapidly. The omission of basic pharmacologic studies to determine the proper dosing may have compromised the effectiveness of 17-hydroxyprogesterone caproate. Future pharmacotherapy trials in pregnancy must first complete fundamental pharmacology studies.

Addressing a broken drug pipeline for preterm birth: why early preterm birth is an orphan disease

Preterm birth remains one of the most urgent unresolved medical problems in obstetrics, yet only 2 therapeutics for preventing preterm birth have ever been approved by the United States Food and Drug Administration, and neither remains on the market. The recent withdrawal of 17-hydroxyprogesterone caproate (17-OHPC, Makena) marks a new but familiar era for obstetrics with no Food and Drug Administration-approved pharmaceuticals to address preterm birth. The lack of pharmaceuticals reflects a broad and ineffective pipeline hindered by extensive regulatory hurdles, soaring costs of performing drug research, and concerns regarding adverse effects among a particularly vulnerable population. The pharmaceutical industry has historically limited investments in research for diseases with similarly small markets, such as cystic fibrosis, given their rarity and diminished projected financial return. The Orphan Drug Act, however, incentivizes drug development for "orphan diseases", defined as affecting <200,000 people in the United States annually. Although the total number of preterm births in the United States exceeds this threshold annually, the early subset of preterm birth (<34 weeks' gestation) would qualify, which is predominantly caused by inflammation and infection. The scientific rationale for classifying preterm birth into early and late subsets is strong given that their etiologies differ, and therapeutics that may be efficacious for one subset may not work for the other. For example, antiinflammatory therapeutics would be expected to be highly effective for early but not late preterm birth. A robust therapeutic pipeline of antiinflammatory drugs already exists, which could be used to target spontaneous early preterm birth, in combination with antibiotics shown to sterilize the amniotic cavity. New applications for therapeutics targeting spontaneous early preterm birth could categorize as orphan disease drugs, which could revitalize the preterm birth therapeutic pipeline. Herein, we describe why drugs targeting early preterm birth should qualify for orphan status, which may increase pharmaceutical interest for this vitally important obstetrical condition.

The inclusion of pregnant women in vaccine clinical trials: An overview of late-stage clinical trials' records between 2018 and 2023

Pregnant women are generally excluded from clinical research over safety concerns. However, demands to include them in clinical vaccine development have intensified after recent COVID-19, Ebola, and Lassa fever outbreaks given the disproportionate effect of these diseases on pregnant women and/or their foetuses. Numerous studies highlighted the scarcity of safety data for therapeutic interventions in pregnant women. Nevertheless, only a small number have assessed the number of vaccine trials including this population. Therefore, we searched for phase 3 and 4 vaccine clinical trials in healthy populations registered between 2018 and 2023 in clinicaltrials.gov and the International Clinical Trial Registry Platform. Out of 400 registered vaccine trials matching our inclusion criteria, 217 (54 %) were industry-sponsored, and 222 (56 %) had COVID-19 as a target. We found 22 studies (6 %) that either were designed for pregnant women or included them as part of a larger population. Out of these 22 trials, 13 were designed specifically for pregnant women; seven of these were maternal vaccines aiming at protecting the foetus, namely pertussis (3), Respiratory Syncytial Virus (RSV) (3), and meningitis plus tetanus (1) vaccines, and six others targeted either flu (3), COVID-19 (2) or Ebola (1). Only the RSV and Ebola vaccine trials were industry-sponsored. We also found that nine studies targeting the general population included pregnant women. These focused on COVID-19 (3), flu (2), COVID-19 + flu (2), Ebola (1), and Hepatitis B (1). None of these studies was industry-sponsored. Our findings show that a gap still exists in terms of pregnant women's inclusion in vaccine trials. Such a gap needs to be tackled urgently to minimise the devastating effects that a future infectious disease outbreak could have on this population. This study can inform future demands for increased inclusion, especially in industry-sponsored trials, as it provides an overview of the current vaccine trials scene.

A Literature Review of Changes in Phase II Drug-Metabolizing Enzyme and Drug Transporter Expression during Pregnancy

The purpose of this literature review is to comprehensively summarize changes in the expression of phase II drug-metabolizing enzymes and drug transporters in both the pregnant woman and the placenta. Using PubMed®, a systematic search was conducted to identify literature relevant to drug metabolism and transport in pregnancy. PubMed was searched with pre-specified terms during the period of 26 May 2023 to 10 July 2023. The final dataset of 142 manuscripts was evaluated for evidence regarding the effect of gestational age and hormonal regulation on the expression of phase II enzymes (n = 16) and drug transporters (n = 38) in the pregnant woman and in the placenta. This comprehensive review exposes gaps in current knowledge of phase II enzyme and drug transporter localization, expression, and regulation during pregnancy, which emphasizes the need for further research. Moreover, the information collected in this review regarding phase II drug-metabolizing enzyme and drug transporter changes will aid in optimizing pregnancy physiologically based pharmacokinetic (PBPK) models to inform dose selection in the pregnant population.

The most common medications dispensed to lactating persons: An electronic health record-based approach

PURPOSE

Using a novel, electronic health record (EHR)-based approach, to estimate the prevalence of prescription medication use at 2, 4, and 6 months postpartum among lactating individuals.

METHODS

We utilized automated EHR data from a US health system that records infant feeding information at well-child visits. We linked mothers who received prenatal care to their infants born May 2018-June 2019, and we required infants to have ≥1 well-child visit between 31 and 90 days of life (i.e., 2-month well-child visit with a ±1 month window). Mothers were classified as lactating at the 2-month well-child visit if their infant received breast milk at the 2-month well-child visit. For subsequent well-child visits at 4 and 6 months, mothers were considered lactating if their infant was still receiving breast milk.

RESULTS

We identified 6013 mothers meeting inclusion criteria, and 4158 (69.2%) were classified as lactating at the 2-month well-child visit. Among those classified as lactating, the most common medication classes dispensed around the 2-month well-child visit were oral progestin contraceptives (19.1%), selective serotonin reuptake inhibitors (8.8%), first generation cephalosporins (4.3%), thyroid hormones (3.5%), nonsteroidal anti-inflammatory agents (3.4%), penicillinase-resistant penicillins (3.1%), topical corticosteroids (2.9%), and oral imidazole-related antifungals (2.0%). The most common medication classes were similar around the 4 and 6-month well-child visits although prevalence estimates were often lower.

CONCLUSIONS

Progestin-only contraceptives, antidepressants, and antibiotics were the most dispensed medications among lactating mothers. With routine collection of breastfeeding information, mother-infant linked EHR data may overcome limitations in previous studies of medication utilization during lactation. These data should be considered for studies of medication safety during lactation given the need for human safety data.

Ethical Considerations for the Delivery of Obstetric and Gynecologic Care During a Pandemic: ACOG Committee Statement No. 6

Obstetrician-gynecologists (ob-gyns) are essential to providing high-quality health care, and this duty remains unchanged during pandemics. This Committee Statement discusses ethics related to the provision of obstetric and gynecologic care during a pandemic caused by a highly transmissible pathogen. As health care guidelines related to pandemics are created by institutions, ob-gyns have a responsibility to advocate for obstetric and gynecologic health priorities. Additionally, many clinical practice decisions made to reduce the spread of the infectious agent and maximize physicians' ability to care for those who need help will have ramifications on patient satisfaction, the patient-physician relationship, and equity in health outcomes. Obstetrician-gynecologists are obligated to protect themselves, their patients, and others by using appropriate protective measures (such as personal protective equipment and diagnostic testing) and observing institutional, state, and federal guidelines for the appropriate isolation and care of patients with suspected or confirmed disease.

Use of Physiologically Based Pharmacokinetic Modeling for Hepatically Cleared Drugs in Pregnancy: Regulatory Perspective

Physiologically based pharmacokinetic modeling could be used to predict changes in exposure during pregnancy and possibly inform medicine use in pregnancy in situations in which there is currently limited or no available clinical PK data. The Medicines and Healthcare Product Regulatory Agency has been evaluating the available models for a number of medicines cleared by hepatic clearance mechanisms. Models were evaluated for metoprolol, tacrolimus, clindamycin, ondansetron, phenytoin, caffeine, fluoxetine, clozapine, carbamazepine, metronidazole, and paracetamol. The hepatic metabolism through cytochrome P450 (CYP) contributes significantly to the elimination of these drugs, and available knowledge of CYP changes during pregnancy has been implemented in the existing pregnancy physiology models. In general, models were able to capture trends in exposure changes in pregnancy to some extent, but the magnitude of pharmacokinetic change for these hepatically cleared drugs was not captured in each case, nor were models always able to capture overall exposure in the populations. A thorough evaluation was hampered by the lack of clinical data for drugs cleared by a specific clearance pathway. The limited clinical data, as well as complex elimination pathways involving CYPs, uridine 5'-diphospho-glucuronosyltransferase and active transporter for many drugs, currently limit the confidence in the prospective use of the models. Pregnancy-related changes in uridine 5'-diphospho-glucuronosyltransferase and transport functions are emerging, and incorporation of such changes in current physiologically based pharmacokinetic modeling software is in progress. Filling this gap is expected to further enhance predictive performance of models and increase the confidence in predicting PK changes in pregnant women for hepatically cleared drugs.

Association of postpartum medication practices with early breastfeeding cessation among mothers with chronic conditions: A prospective cohort study

INTRODUCTION

Use of medications is a common concern for breastfeeding women, particularly when they are strongly needed or unavoidable to manage maternal chronic conditions. Yet the influence of medication usage patterns on breastfeeding duration in mothers with chronic conditions is unclear. The objective of this study was to examine whether postpartum medication practices were associated with shorter breastfeeding duration or earlier than planned breastfeeding cessation among mothers with chronic conditions.

MATERIAL AND METHODS

We analyzed 346 mothers with chronic conditions enrolled in a prospective, community-based pregnancy cohort study (Alberta, Canada) who initiated breastfeeding after birth. Data were collected through self-report questionnaires spanning late pregnancy to 6 months postpartum. Based on reported use of preexisting medications while breastfeeding, women were classified as continuing medications (reference group), discontinuing one or more medications, or those who did not use preexisting medications. Cox proportional hazards regression was used to analyze the association of medication practices and overall breastfeeding duration in weeks. Logistic regression was used to analyze the association of medication practices and earlier than planned breastfeeding cessation. Multivariable models adjusted for demographic and health-related factors.

RESULTS

Overall, 30.6% of women with chronic conditions stopped breastfeeding in the first 6 months, almost all of whom did so earlier than planned. In multivariable models, medication discontinuation was significantly associated with shorter breastfeeding duration (adjusted hazard ratio [HR] 1.67, 95% confidence interval [CI] 1.03-2.70) and earlier than planned breastfeeding cessation (adjusted odds ratio [OR] 1.85, 95% CI 1.01-3.42), whereas medication non-use was not associated with differences in breastfeeding outcomes.

CONCLUSIONS

Women with chronic conditions who discontinued preexisting medications while breastfeeding had significantly shorter breastfeeding duration and were less likely to meet their breastfeeding goals in the first 6 months postpartum compared to women who continued preexisting medications.

Behaviors Related to Medication Safety and Use During Pregnancy

Background: Most women take medication during pregnancy despite limited scientific evidence on safety. We investigated medication use, including changes in and reasons for changes in use during pregnancy, with attention to medication use in pregnant women with chronic conditions. Materials and Methods: We conducted an online survey of pregnant women aged ≥18 years (n = 1,226). We calculated descriptive statistics for aspects of medication use and performed multivariable logistic regression to examine associations between change in use and chronic conditions. Results: Seventy-nine percent of women took at least one medication during pregnancy. Among those, 63.2% made at least one medication change: 42.0% started, 34.9% stopped, 30.0% missed dose(s), and 18.1% lowered dose(s) from that originally prescribed or recommended. More than a third (36.5%) of women who stopped, lowered, or missed medication did so independent of health care provider advice; 54.0% cited concern about birth or developmental defects as reasons for change. Odds of medication change were higher for women with chronic conditions: digestive conditions-starting (adjusted odds ratio [AOR] = 1.8, 95% confidence interval [CI] = 1.1-2.7), stopping (AOR = 2.1, 95% CI = 1.4-3.3), and lowering (AOR = 2.4, 95% CI = 1.7-3.3) medication; mental health conditions-starting (AOR = 1.6, 95% CI = 1.2-2.2), stopping (AOR = 3.0, 95% CI = 2.3-4.0), or missing (AOR = 2.1, 95% CI = 1.6-2.8) medication; pain conditions-stopping (AOR = 2.9, 95% CI = 2.0-4.2); and respiratory conditions-starting (AOR = 2.0, 95% CI = 1.3-3.1), stopping (AOR = 1.7, 95% CI = 1.1-2.6), and missing (AOR = 2.2, 95% CI = 1.4-3.4) medication. Conclusions: Most pregnant women take medication and many, including those with chronic conditions, change their medication use during pregnancy. Medication change may occur independent of health care provider advice and due to women's safety concerns.

Pharmacokinetic data in pregnancy: A review of available literature data and important considerations in collecting clinical data

Pregnancy-related physiological changes can alter the absorption, distribution, metabolism and excretion of medicines which may affect the safety and efficacy of the medicines administered in pregnancy. Pharmacokinetic data can thus be instrumental in supporting dose adjustments required in this population. This review considers the availability of published pharmacokinetic data for over 200 medicines of interest for use in pregnancy in the UK, to identify whether sufficient data currently exists, in principle, for any medicine or group of medicines to support dose adjustments to maintain maternal health through pregnancy. Very limited data was found for many of the medicines of interest. Nevertheless, well documented, large changes of exposure for some drugs, where data is available, highlights the urgent need to collect more data of good quality to inform appropriate doses, when needed, in this population. In addition, clinical study methodology can have an impact on the usefulness of the data and key clinical design aspects are highlighted for consideration in future clinical study design.

The Use of Pregnancy Physiologically Based Pharmacokinetic Modeling for Renally Cleared Drugs

Physiologically based pharmacokinetic modeling (PBPK) could be used to predict changes in exposure during pregnancy and possibly inform medicine use in pregnancy in situations where there are currently no available clinical data. The Medicines and Healthcare Product Regulatory Agency has been evaluating the available models for a number of medicines cleared by the kidney. Models were evaluated for ceftazidime, cefuroxime, metformin, oseltamivir, and amoxicillin. Because the passive renal process contributes significantly to the renal elimination of these drugs and changes of the process during pregnancy have been implemented in existing pregnancy physiology models, simulations using these models can reasonably describe the pharmacokinetics of ceftazidime changes during pregnancy and appears to generally capture the changes in the other medicines; however, there are insufficient data on drugs solely passively cleared to fully qualify the models. In addition, in many cases, active transport processes are involved in a drug's renal clearance. Knowledge of changes in renal transport functions during pregnancy is emerging, and incorporation of such changes in current physiologically based pharmacokinetic modeling software is a work in progress. Filling this gap is expected to further enhance predictive performance of the models and increase the confidence in predicting pharmacokinetic changes in pregnant women for other renally cleared drugs.

Human Milk and Plasma Pharmacokinetics of Single-Dose Rimegepant 75 mg in Healthy Lactating Women

Objective: Investigate whether rimegepant-an oral small molecule calcitonin gene-related peptide receptor antagonist for the treatment of migraine-is excreted in human milk after a single 75 mg dose and characterize its concentration-time profile in the plasma and milk of healthy lactating women to determine the relative infant dose (RID). Methods: This open-label, single-center study enrolled healthy lactating women aged 18-40 years with a gestation of 37-42 weeks and uncomplicated delivery of a single healthy child ≥2 weeks (14 days) and ≤6 months before study drug administration. Plasma samples were collected 0, 1, 2, 4, and 8 hours postdose; human milk samples were collected at 0, 1, 2, 4, 8, 12, 16, 24, 32, and 36 hours. The milk:plasma drug concentration ratio was estimated as the ratio of the human milk:plasma areas under the curve. The RID (%) was calculated as 100 times the quotient of the body weight-normalized infant and maternal doses. Results: Subjects (N = 12) were enrolled between 25 January and 15 September 2020. The mean (standard deviation [SD]) age was 29.8 (3.6) years; mean (SD) body mass index was 26.8 (4.9) kg/m². The mean (SD) RID of rimegepant was 0.51% (0.14). The mean (SD) body-weight normalized infant dose was 0.005 (0.001) mg/kg/day, the mean (SD) body-weight normalized maternal dose was 1.04 (0.18) mg/kg/day, and mean (SD) maternal body weight was 74.0 (13.3) kg. Conclusion: On a weight-adjusted basis, the mean RID of rimegepant was <1% of the maternal dose.