Clinical therapeutics in pregnancy

Availability of Safe and Effective Therapeutic Options to Pregnant and Lactating Individuals Following the United States Food and Drug Administration Pregnancy and Lactation Labeling Rule

OBJECTIVE

To explore the extent and type of pregnancy and lactation data of newly approved prescription drugs and assess whether the presented recommendations are data-driven, as required by the US Food and Drug Administration Pregnancy and Lactation Labeling Rule implemented in 2015.

STUDY DESIGN

In this descriptive analysis, we reviewed pregnancy and lactation data of all new molecular entities approved between 2001 and 2020 in their most updated labeling. Information was collected regarding the pregnancy and lactation risk statements, the source of pregnancy and lactation data, and the design and methods of pregnancy and lactation studies in the labeling.

RESULTS

Of the 422 new molecular entities, the key advisory statement for use of 133 (32%) drugs in pregnancy and 194 (46%) drugs in lactation were classified as "against use." Less than 2% of all drugs had a key advisory statement that supported their use during pregnancy or lactation. The sources of data regarding use in pregnancy were studies in human and animals in 46 (11%) and 348 (82%) drugs, respectively. For use during lactation, data included studies in human and animals in 23 (5%) and 251 (59%) drugs, respectively. The key advisory recommendation was consistent with the available human information in 4 (8%) drugs in pregnancy and 3 (13%) drugs in lactation. Prescription drug labeling contains limited data to support informed decision-making for the use of prescription drugs during pregnancy/lactation. Close collaboration among stakeholders is required to enhance the availability of data in this population.

Translating Clinical Pharmacology Data in Pregnancy to Evidence-Based Guideline Recommendations: Perspectives From the HIV Field

Pharmacokinetic (PK) studies in pregnant, postpartum, and breastfeeding people are critical to informing appropriate medication use and dosing. A key component of translating PK results in these complex populations into clinical practice involves the systematic review and interpretation of data by guideline panels, composed of clinicians, scientists, and community members, to leverage available data for informed decision making by clinicians and patients and offer clinical best practices. Interpretation of PK data in pregnancy involves evaluation of multiple factors such as the study design, target population, and type of sampling performed. Assessments of fetal and infant drug exposure while in utero or during breastfeeding, respectively, are also critical for informing whether medications are safe to use during pregnancy and throughout postpartum in lactating people. This review will provide an overview of this translational process, discussion of the various factors considered by guideline panels, and practical aspects of implementing certain recommendations, using the HIV field as an example.

Bedaquiline exposure in pregnancy and breastfeeding in women with rifampicin-resistant tuberculosis

AIMS

We aimed to explore the effect of pregnancy on bedaquiline pharmacokinetics (PK) and describe bedaquiline exposure in the breast milk of mothers treated for rifampicin-resistant tuberculosis (TB), where there are no human data available.

METHODS

We performed a longitudinal PK study in pregnant women treated for rifampicin-resistant TB to explore the effect of pregnancy on bedaquiline exposure. Pharmacokinetic sampling was performed at 4 time-points over 6 hours in the third trimester, and again at approximately 6 weeks postpartum. We obtained serial breast milk samples from breastfeeding mothers, and a single plasma sample taken from breastfed and nonbreastfed infants to assess bedaquiline exposure. We used liquid chromatography-tandem mass spectrometry to perform the breast milk and plasma bedaquiline assays, and population PK modelling to interpret the bedaquiline concentrations.

RESULTS

We recruited 13 women, 6 of whom completed the ante- and postpartum PK sampling. All participants were HIV-positive on antiretroviral therapy. We observed lower ante- and postpartum bedaquiline exposures than reported in nonpregnant controls. Bedaquiline concentrations in breast milk were higher than maternal plasma (milk to maternal plasma ratio: 14:1). A single random plasma bedaquiline and M2 concentration was available in 4 infants (median age: 6.5 wk): concentrations in the 1 breastfed infant were similar to maternal plasma concentrations; concentrations in the 3 nonbreastfed infants were detectable but lower than maternal plasma concentrations.

CONCLUSION

We report low exposure of bedaquiline in pregnant women treated for rifampicin-resistant TB. Bedaquiline significantly accumulates in breast milk; breastfed infants receive mg/kg doses of bedaquiline equivalent to maternal doses.

The Person's Care Requires a Sex and Gender Approach

There is an urgent need to optimize pharmacology therapy with a consideration of high interindividual variability and economic costs. A sex-gender approach (which considers men, women, and people of diverse gender identities) and the assessment of differences in sex and gender promote global health, avoiding systematic errors that generate results with low validity. Care for people should consider the single individual and his or her past and present life experiences, as well as his or her relationship with care providers. Therefore, intersectoral and interdisciplinary studies are urgently required. It is desirable to create teams made up of men and women to meet the needs of both. Finally, it is also necessary to build an alliance among regulatory and ethic authorities, statistics, informatics, the healthcare system and providers, researchers, the pharmaceutical and diagnostic industries, decision makers, and patients to overcome the gender gap in medicine and to take real care of a person in an appropriate manner.

Using a Composite Maternal-Infant Outcome Measure in Tuberculosis-Prevention Studies Among Pregnant Women

BACKGROUND

Tuberculosis (TB-)-preventive therapy (TPT) among pregnant women reduces risk of TB in mothers and infants, but timing of initiation should consider potential adverse effects. We propose an analytical approach to evaluate the risk-benefit of interventions.

METHODS

A novel outcome measure that prioritizes maternal and infant events was developed with a 2-stage Delphi survey, where a panel of stakeholders assigned scores from 0 (best) to 100 (worst) based on perceived desirability. Using data from TB APPRISE, a trial among pregnant women living with human immunodeficiency virus (WLWH) that randomized the timing of initiation of isoniazid, antepartum versus postpartum, was evaluated.

RESULTS

The composite outcome scoring/ranking system categorized mother-infant paired outcomes into 8 groups assigned identical median scores by stakeholders. Maternal/infant TB and nonsevere adverse pregnancy outcomes were assigned similar scores. Mean (SD) composite outcome scores were 43.7 (33.0) and 41.2 (33.7) in the antepartum and postpartum TPT initiation arms, respectively. However, a modifying effect of baseline antiretroviral regimen was detected (P = .049). When women received nevirapine, composite scores were higher (worse outcomes) in the antepartum versus postpartum arms (adjusted difference, 14.3; 95% confidence interval [CI], 2.4-26.2; P = .02), whereas when women received efavirenz there was no difference by timing of TPT (adjusted difference, .62; 95% CI, -3.2-6.2; P = .53).

CONCLUSIONS

For TPT, when used by otherwise healthy persons, preventing adverse events is paramount from the perspective of stakeholders. Among pregnant WLWH in high-TB-burden regions, it is important to consider the antepartum antiretroviral regimen taken when deciding when to initiate TPT. Clinical Trials Registration. NCT01494038 (IMPAACT P1078).

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.

Maternal Serotonin Reuptake Inhibitor Antidepressants Have Acute Effects on Fetal Heart Rate Variability in Late Gestation

Background: Prenatal exposure to serotonin reuptake inhibitor (SRI) antidepressants increases risk for adverse neurodevelopmental outcomes, yet little is known about whether effects are present before birth. In relation to maternal SRI pharmacokinetics, this study investigated chronic and acute effects of prenatal SRI exposure on third-trimester fetal heart rate variability (HRV), while evaluating confounding effects of maternal depressed mood. Methods: At 36-weeks' gestation, cardiotocograph measures of fetal HR and HRV were obtained from 148 pregnant women [four groups: SRI-Depressed (n = 31), SRI-Non-Depressed (n = 18), Depressed (unmedicated; n = 42), and Control (n = 57)] before, and ~5-h after, typical SRI dose. Maternal plasma drug concentrations were quantified at baseline (pre-dose) and four time-points post-dose. Mixed effects modeling investigated group differences between baseline/pre-dose and post-dose fetal HR outcomes. Post hoc analyses investigated sex differences and dose-dependent SRI effects. Results: Maternal SRI plasma concentrations were lowest during the baseline/pre-dose fetal assessment (trough) and increased to a peak at the post-dose assessment; concentration-time curves varied widely between individuals. No group differences in fetal HR or HRV were observed at baseline/pre-dose; however, following maternal SRI dose, short-term HRV decreased in both SRI-exposed fetal groups. In the SRI-Depressed group, these post-dose decreases were displayed by male fetuses, but not females. Further, episodes of high HRV decreased post-dose relative to baseline, but only among SRI-Non-Depressed group fetuses. Higher maternal SRI doses also predicted a greater number of fetal HR decelerations. Fetuses exposed to unmedicated maternal depressed mood did not differ from Controls. Conclusions: Prenatal SRI exposure had acute post-dose effects on fetal HRV in late gestation, which differed depending on maternal mood response to SRI pharmacotherapy. Importantly, fetal SRI effects were sex-specific among mothers with persistent depressive symptoms, as only male fetuses displayed acute HRV decreases. At trough (pre-dose), chronic fetal SRI effects were not identified; however, concurrent changes in maternal SRI plasma levels suggest that fetal drug exposure is inconsistent. Acute SRI-related changes in fetal HRV may reflect a pharmacologic mechanism, a transient impairment in autonomic functioning, or an early adaption to altered serotonergic signaling, which may differ between males and females. Replication is needed to determine significance with postnatal development.

Nonprescription drugs recommended in guidelines for common pain conditions

Evidence-based pain guidelines allow recommendation of nonprescription analgesics to patients, facilitating self-care. We researched clinical practice guidelines for common conditions on websites of pain associations, societies, health institutions and organizations, PubMed, ProQuest, Embase, Google Scholar until April 2019. We wanted to determine whether there is a consensus between guidelines. From 114 identified guidelines, migraine (27) and osteoarthritis (26) have been published most around the world, while dysmenorrhea (14) is mainly discussed in developing countries. Specific recommendations to pregnant women, children and older people predominantly come from the UK and USA. We found that acetaminophen and oral nonsteroidal anti-inflammatory drugs (NSAIDs) represent first-line management across all pain conditions in adults and children. In osteoarthritis, topical NSAIDs should be considered before oral NSAIDs. This knowledge might persuade patients that using these drugs first could enable fast and effective pain relief.

Review of Cardiovascular Drugs in Pregnancy

Cardiovascular disease is now the leading cause of pregnancy-related deaths in the United States. Increasing maternal mortality in the United States underscores the importance of proper cardiovascular management. Significant physiological changes during pregnancy affect the heart's ability to respond to pathological processes such as hypertension and heart failure. These physiological changes further affect the pharmacokinetic and pharmacodynamic properties of cardiac medications. During pregnancy, these changes can significantly alter medication efficacy and metabolism. This article systematically reviews the literature on safety, efficacy, pharmacokinetics, and pharmacodynamics of cardiovascular drugs used for hypertension and heart failure during pregnancy and lactation. The 2017 American College of Cardiology/American Heart Association hypertension guidelines recommend transitioning pregnant patients to methyldopa, nifedipine, or labetalol. Heart failure medications, including beta-blockers, furosemide, and digoxin, are relatively safe and can be used effectively. Medications that block the renin angiotensin-aldosterone system have been shown to be beneficial in the general population; however, they are teratogenic and, therefore, contraindicated in pregnancy. Cardiovascular medications can also enter breast milk and, therefore, care must be taken when selecting drugs during the lactation period. A summary of the safety of drugs during pregnancy and lactation from an online resource, LactMed by the National Library of Medicine's TOXNET database, is included. High-risk pregnant patients with cardiovascular disease require a multispecialty team of doctors, including health care providers from obstetrics and gynecology, maternal fetal medicine, internal medicine, cardiovascular disease specialists, and specialized pharmacology expertise.

Effect of Maternal Obesity on Maternal-Fetal Transfer of Preoperative Cefazolin at Cesarean Section

OBJECTIVES

American Congress of Obstetricians and Gynecologists recommends a single dose of antibiotic prophylaxis before all cesarean sections (C/S). This recommendation is based on pharmacokinetic studies that include only non-obese patients. We sought to evaluate 1) cefazolin plasma concentrations among obese and non-obese patients after administration of a 2-g cefazolin dose for prevention of surgical wound infections, and 2) whether cefazolin concentration in fetal circulation may be protective against pathogens that cause early onset neonatal sepsis.

METHODS

Maternal and fetal cefazolin plasma concentrations were compared between obese (body mass index [BMI] ≥ 30 kg/m²) and non-obese (BMI < 25 kg/m²) healthy, term pregnant women undergoing scheduled C/S. Liquid chromatographic-tandem mass spectrometric (LC-MS/MS) methods were used for quantification of total and free cefazolin concentrations in maternal blood (MB) and umbilical cord blood (UCB).

RESULTS

Eight women were screened and consented. There was no difference between groups in MB total and free cefazolin concentrations. All MB samples had total and free cefazolin concentrations greater than the minimum inhibitory concentration 90 (MIC90) for Group B Streptococcus (GBS), Staphylococcus aureus, and Escherichia coli. All UCB samples had total and free cefazolin concentrations greater than MIC90 for GBS and S aureus, even when administered as briefly as 18 minutes before delivery. A lower concentration of total cefazolin was detected in UCB of neonates of obese women compared to non-obese women (p > 0.05).

CONCLUSIONS

Administration of 2 g of cefazolin to women undergoing scheduled C/S might be an adequate prophylactic dose for surgical wound infection in both non-obese and obese patients; and cefazolin concentration in fetal circulation may be protective against GBS and S aureus.

Enantiomer-specific ketorolac pharmacokinetics in young women, including pregnancy and postpartum period

Racemic ketorolac clearance (CL) is significantly higher at delivery, but S-ketorolac disposition determines the analgesic effects. The aim of this study was to investigate the effect of pregnancy and postpartum period on enantiomer-specific (S and R) intravenous (IV) ketorolac pharmacokinetics (PKs). Data in women shortly following cesarean delivery (n=39) were pooled with data in a subgroup of these women that was reevaluated in the later postpartum period (postpartum group, n=8/39) and with eight healthy female volunteers. All women received single IV bolus of 30 mg ketorolac tromethamine. Five plasma samples were collected at 1, 2, 4, 6, and 8 hours and plasma concentrations were determined using high performance liquid chromatography. Enantiomer-specific PKs were calculated using PKSolver. Unpaired analysis showed that distribution volume at steady state (Vss, L/kg) for S- and R-ketorolac was significantly higher in women shortly following cesarean delivery (n=31) compared to postpartum group (n=8) or to healthy female volunteers (n=8). CL, CL to body weight, and CL to body surface area (CL/BSA) for S- and R-ketorolac were also significantly higher in women following delivery. In addition, S/R-ketorolac CL/BSA ratio was significantly higher at delivery. Paired PK analysis in eight women shortly following delivery and in postpartum group showed the same pattern. Finally, the simultaneous increase in CL and Vss resulted in similar estimates for elimination half-life in both unpaired and paired analysis. In conclusion, pregnancy affects S-, R-, and S/R-ketorolac disposition. This is of clinical relevance since S-ketorolac (analgesia) CL is even more increased compared to R-ketorolac CL, and S/R-ketorolac CL ratio is higher following delivery compared to postpartum period or to healthy female volunteers.

Pregnant women with substance use disorders: The intersection of history, ethics, and advocacy

Pregnant women with substance use disorders face many obstacles, including obtaining evidence-based treatment and care. This article (1) briefly reviews the history of pregnant women in clinical trials and substance use disorders treatment research; (2) identifies current ethical issues facing researchers studying pregnant women with substance use disorders; (3) presents and describes an ethical framework to utilize; and (4) identifies future directions needed to develop appropriate research and treatment policies and practices. Current research is not providing enough information to clinicians, policy-makers, and the public about maternal and child health and substance use disorders, and the data will not be sufficient to offer maximum benefit until protocols are changed.

Maternal Pharmacokinetics and Fetal Disposition of (±)-Citalopram during Mouse Pregnancy

While selective-serotonin reuptake inhibitor (SSRI) antidepressants are commonly prescribed in the treatment of depression, their use during pregnancy leads to fetal drug exposures. According to recent reports, such exposures could affect fetal development and long-term offspring health. A central question is how pregnancy-induced physical and physiological changes in mothers, fetuses, and the placenta influence fetal SSRI exposures during gestation. In this study, we examined the effects of gestational stage on the maternal pharmacokinetics and fetal disposition of the SSRI (±)-citalopram (CIT) in a mouse model. We determined the maternal and fetal CIT serum concentration-time profiles following acute maternal administration on gestational days (GD)14 and GD18, as well as the fetal brain drug disposition. The results show that pregnancy affects the pharmacokinetics of CIT and that maternal drug clearance increases as gestation progresses. The data further show that CIT and its primary metabolite desmethylcitalopram (DCIT) readily cross the placenta into the fetal compartment, and fetal exposure to CIT exceeds that of the mother during gestation 2 h after maternal administration. Enzymatic activity assays revealed that fetal drug metabolic capacity develops in late gestation, resulting in elevated circulating and brain concentrations of DCIT at embryonic day (E)18. Fetal exposure to the SSRI CIT in murine pregnancy is therefore influenced by both maternal gestational stage and embryonic development, suggesting potential time-dependent effects on fetal brain development.

Raltegravir in HIV-1-Infected Pregnant Women: Pharmacokinetics, Safety, and Efficacy

BACKGROUND

The use of raltegravir in human immunodeficiency virus (HIV)-infected pregnant women is important in the prevention of mother-to-child HIV transmission, especially in circumstances when a rapid decline of HIV RNA load is warranted or when preferred antiretroviral agents cannot be used. Physiological changes during pregnancy can reduce antiretroviral drug exposure. We studied the effect of pregnancy on the pharmacokinetics of raltegravir and its safety and efficacy in HIV-infected pregnant women.

METHODS

An open-label, multicenter, phase 4 study in HIV-infected pregnant women receiving raltegravir 400 mg twice daily was performed (Pharmacokinetics of Newly Developed Antiretroviral Agents in HIV-Infected Pregnant Women Network). Steady-state pharmacokinetic profiles were obtained in the third trimester and postpartum along with cord and maternal delivery concentrations. Safety and virologic efficacy were evaluated.

RESULTS

Twenty-two patients were included, of which 68% started raltegravir during pregnancy. Approaching delivery, 86% of the patients had an undetectable viral load (<50 copies/mL). None of the children were HIV-infected. Exposure to raltegravir was highly variable. Overall area under the plasma concentration-time curve (AUC) and plasma concentration at 12 hours after intake (C12h) plasma concentrations in the third trimester were on average 29% and 36% lower, respectively, compared with postpartum: Geometric mean ratios (90% confidence interval) were 0.71 (.53-.96) for AUC0-12h and 0.64 (.34-1.22) for C12h. The median ratio of raltegravir cord to maternal blood was 1.21 (interquartile range, 1.02-2.17; n = 9).

CONCLUSIONS

Raltegravir was well tolerated during pregnancy. The pharmacokinetics of raltegravir showed extensive variability. The observed mean decrease in exposure to raltegravir during third trimester compared to postpartum is not considered to be of clinical importance. Raltegravir can be used in standard dosages in HIV-infected pregnant women.

CLINICAL TRIALS REGISTRATION

NCT00825929.

Use and impact of cardiac medication during pregnancy

ABSTRACT 

Cardiovascular disease is the most encountered cause of maternal death during pregnancy in the western world and an increase in maternal mortality due to cardiac causes has been observed. More women with congenital or acquired heart disease have the desire to become pregnant. Pregnancy is known to impose a major hemodynamic burden and also has impacts on the coagulation system. The risk of developing complications is clearly increased as compared with the normal population. For optimal management, it is crucial to have information on the effects of cardiac medications on the fetus. The focus of this article is to discuss the management of cardiac disease in pregnancy, as well as the known safety of cardiac medications for the mother and/or fetus.

Concentrations of venlafaxine and its main metabolite O-desmethylvenlafaxine during pregnancy

WHAT IS KNOWN AND OBJECTIVE

Depression during pregnancy is common and includes risks for mother and child. Pharmacokinetics of venlafaxine may be changed during pregnancy. This study aimed to describe changes in metabolic ratios and concentrations of venlafaxine and its main metabolite O-desmethylvenlafaxine during and after pregnancy.

METHODS

To study this, we used data from our study of compliance to Antidepressants During Pregnancy (the ADAP study) to investigate the course of venlafaxine and O-desmethylvenlafaxine concentrations during pregnancy and in the period post-partum.

RESULTS AND DISCUSSION

We found that the venlafaxine concentration significantly changed during pregnancy when compared to the post-partum period (P = 0·028). The median concentration of venlafaxine in the first trimester was 98·9% (54·2-292·0%), the second 100·0% (46·5-264·0%) and the third trimester 87·0% (61·5-217·2%). We did not found differences in O-desmethylvenlafaxine concentrations in the different trimesters of pregnancy compared with the post-partum period, P = 0·565. Also the ratio of O-desmethylvenlafaxine/venlafaxine concentrations increased significantly from 76·9% (range 32·8-142·0%) in the first trimester to 196·7% (range 83·3-427·6%) in the third trimester compared with the post-partum period, P = 0·004. Further, three of seven patients had concentrations below the therapeutic reference range (100-400 μg/L) in any period of pregnancy, whereas no one had subtherapeutic concentrations in the post-partum period.

WHAT IS NEW AND CONCLUSION

Venlafaxine concentrations decreases during pregnancy, and the ratio of the concentrations of O-desmethylvenlafaxine/venlafaxine increases during pregnancy. Pregnant women using venlafaxine are at risk for subtherapeutic concentrations, therefore routine monitoring of concentrations venlafaxine and O-desmethylvenlafaxine is recommendable during pregnancy.

Maternal-fetal disposition of glyburide in pregnant mice is dependent on gestational age

Gestational diabetes mellitus is a major complication of human pregnancy. The oral clearance (CL) of glyburide, an oral antidiabetic drug, increases 2-fold in pregnant women during late gestation versus nonpregnant controls. In this study, we examined gestational age-dependent changes in maternal-fetal pharmacokinetics (PK) of glyburide and metabolites in a pregnant mouse model. Nonpregnant and pregnant FVB mice were given glyburide by retro-orbital injection. Maternal plasma was collected over 240 minutes on gestation days (gd) 0, 7.5, 10, 15, and 19; fetuses were collected on gd 15 and 19. Glyburide and metabolites were quantified using high-performance liquid chromatography-mass spectrometry, and PK analyses were performed using a pooled data bootstrap approach. Maternal CL of glyburide increased approximately 2-fold on gd 10, 15, and 19 compared with nonpregnant controls. Intrinsic CL of glyburide in maternal liver microsomes also increased as gestation progressed. Maternal metabolite/glyburide area under the curve ratios were generally unchanged or slightly decreased throughout gestation. Total fetal exposure to glyburide was <5% of maternal plasma exposure, and was doubled on gd 19 versus gd 15. Fetal metabolite concentrations were below the limit of assay detection. This is the first evidence of gestational age-dependent changes in glyburide PK. Increased maternal glyburide clearance during gestation is attributable to increased hepatic metabolism. Metabolite elimination may also increase during pregnancy. In the mouse model, fetal exposure to glyburide is gestational age-dependent and low compared with maternal plasma exposure. These results indicate that maternal glyburide therapeutic strategies may require adjustments in a gestational age-dependent manner if these same changes occur in humans.

Sources of interindividual variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in other individuals. A major source of this variability in drug response is drug metabolism, where differences in pre-systemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C max, and/or C min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is well recognized that both intrinsic (such as genetics, age, sex, and disease states) and extrinsic (such as diet, chemical exposures from the environment, and even sunlight) factors play a significant role. For the family of cytochrome P450 enzymes, the most critical of the drug metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, up- and down-regulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less reliably predictable and time-dependent manner. Understanding the mechanistic basis for drug disposition and response variability is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that brings with it true improvements in health outcomes in the therapeutic treatment of disease.

Relationships of chemical concentrations in maternal and cord blood: a review of available data

The developing fetus is likely to be exposed to the same environmental chemicals as the mother during critical periods of growth and development. The degree of maternal-fetal transfer of chemical compounds will be affected by chemical and physical properties such as lipophilicity, protein binding, and active transport mechanisms that influence absorption and distribution in maternal tissues. However, these transfer processes are not fully understood for most environmental chemicals. This review summarizes reported data from more than 100 studies on the ratios of cord:maternal blood concentrations for a range of chemicals including brominated flame-retardant compounds, polychlorinated biphenyls (PCB), polychlorinated dibenzodioxins and dibenzofurans, organochlorine pesticides, perfluorinated compounds, polyaromatic hydrocarbons, metals, and tobacco smoke components. The studies for the chemical classes represented suggest that chemicals frequently detected in maternal blood will also be detectable in cord blood. For most chemical classes, cord blood concentrations were found to be similar to or lower than those in maternal blood, with reported cord:maternal ratios generally between 0.1 and 1. Exceptions were observed for selected brominated flame-retardant compounds, polyaromatic hydrocarbons, and some metals, for which reported ratios were consistently greater than 1. Careful interpretation of the data in a risk assessment context is required because measured concentrations of environmental chemicals in cord blood (and thus the fetus) do not necessarily imply adverse effects or risk. Guidelines and recommendations for future cord:maternal blood biomonitoring studies are discussed.

Drug metabolism and transport during pregnancy: how does drug disposition change during pregnancy and what are the mechanisms that cause such changes?

There is increasing evidence that pregnancy alters the function of drug-metabolizing enzymes and drug transporters in a gestational-stage and tissue-specific manner. In vivo probe studies have shown that the activity of several hepatic cytochrome P450 enzymes, such as CYP2D6 and CYP3A4, is increased during pregnancy, whereas the activity of others, such as CYP1A2, is decreased. The activity of some renal transporters, including organic cation transporter and P-glycoprotein, also appears to be increased during pregnancy. Although much has been learned, significant gaps still exist in our understanding of the spectrum of drug metabolism and transport genes affected, gestational age-dependent changes in the activity of encoded drug metabolizing and transporting processes, and the mechanisms of pregnancy-induced alterations. In this issue of Drug Metabolism and Disposition, a series of articles is presented that address the predictability, mechanisms, and magnitude of changes in drug metabolism and transport processes during pregnancy. The articles highlight state-of-the-art approaches to studying mechanisms of changes in drug disposition during pregnancy, and illustrate the use and integration of data from in vitro models, animal studies, and human clinical studies. The findings presented show the complex inter-relationships between multiple regulators of drug metabolism and transport genes, such as estrogens, progesterone, and growth hormone, and their effects on enzyme and transporter expression in different tissues. The studies provide the impetus for a mechanism- and evidence-based approach to optimally managing drug therapies during pregnancy and improving treatment outcomes.

A simplified PBPK modeling approach for prediction of pharmacokinetics of four primarily renally excreted and CYP3A metabolized compounds during pregnancy

During pregnancy, a drug's pharmacokinetics may be altered and hence anticipation of potential systemic exposure changes is highly desirable. Physiologically based pharmacokinetics (PBPK) models have recently been used to influence clinical trial design or to facilitate regulatory interactions. Ideally, whole-body PBPK models can be used to predict a drug's systemic exposure in pregnant women based on major physiological changes which can impact drug clearance (i.e., in the kidney and liver) and distribution (i.e., adipose and fetoplacental unit). We described a simple and readily implementable multitissue/organ whole-body PBPK model with key pregnancy-related physiological parameters to characterize the PK of reference drugs (metformin, digoxin, midazolam, and emtricitabine) in pregnant women compared with the PK in nonpregnant or postpartum (PP) women. Physiological data related to changes in maternal body weight, tissue volume, cardiac output, renal function, blood flows, and cytochrome P450 activity were collected from the literature and incorporated into the structural PBPK model that describes HV or PP women PK data. Subsequently, the changes in exposure (area under the curve (AUC) and maximum concentration (C max)) in pregnant women were simulated. Model-simulated PK profiles were overall in agreement with observed data. The prediction fold error for C max and AUC ratio (pregnant vs. nonpregnant) was less than 1.3-fold, indicating that the pregnant PBPK model is useful. The utilization of this simplified model in drug development may aid in designing clinical studies to identify potential exposure changes in pregnant women a priori for compounds which are mainly eliminated renally or metabolized by CYP3A4.

Pharmacokinetics of tacrolimus during pregnancy

BACKGROUND

Information on the pharmacokinetics of tacrolimus during pregnancy is limited to case reports despite the increasing number of pregnant women being prescribed tacrolimus for immunosuppression.

METHODS

Blood, plasma, and urine samples were collected over 1 steady-state dosing interval from women treated with oral tacrolimus during early to late pregnancy (n = 10) and postpartum (n = 5). Total and unbound tacrolimus as well as metabolite concentrations in blood and plasma were assayed by a validated liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method. A mixed-effect linear model was used for comparison across gestational age and using postpartum as the reference group.

RESULTS

The mean oral clearance (CL/F) based on whole-blood tacrolimus concentration was 39% higher during mid-pregnancy and late pregnancy compared with postpartum (47.4 ± 12.6 vs. 34.2 ± 14.8 L/h, P < 0.03). Tacrolimus-free fraction increased by 91% in plasma (f(P)) and by 100% in blood (f(B)) during pregnancy (P = 0.0007 and 0.002, respectively). Increased fP was inversely associated with serum albumin concentration (r = -0.7, P = 0.003), which decreased by 27% during pregnancy. Pregnancy-related changes in f(P) and f(B) contributed significantly to the observed gestational increase in tacrolimus whole-blood CL/F (r² = 0.36 and 0.47, respectively, P < 0.01). In addition, tacrolimus whole-blood CL/F was inversely correlated with both hematocrit and red blood cell counts, suggesting that binding of tacrolimus to erythrocytes restricts its availability for metabolism. Treating physicians increased tacrolimus dosages in study participants during pregnancy by an average of 45% to maintain tacrolimus whole-blood trough concentrations in the therapeutic range. This led to striking increases in unbound tacrolimus trough concentrations and unbound area under the concentration-time curve, by 112% and 173%, respectively, during pregnancy (P = 0.02 and 0.03, respectively).

CONCLUSIONS

Tacrolimus pharmacokinetics are altered during pregnancy. Dose adjustment to maintain whole-blood tacrolimus concentration in the usual therapeutic range during pregnancy increases circulating free drug concentrations, which may impact clinical outcomes.

The status of pharmacometrics in pregnancy: highlights from the 3(rd) American conference on pharmacometrics

Physiological changes during pregnancy may alter drug pharmacokinetics. Therefore, mechanistic understanding of these changes and, ultimately, clinical studies in pregnant women are necessary to determine if and how dosing regimens should be adjusted. Because of the typically limited number of patients who can be recruited in this patient group, efficient design and analysis of these studies is of special relevance. This paper is a summary of a conference session organized at the American Conference of Pharmacometrics in April 2011, around the topic of applying pharmacometric methodology to this important problem. The discussion included both design and analysis of clinical studies during pregnancy and in silico predictions. An overview of different pharmacometric methods relevant to this subject was given. The impact of pharmacometrics was illustrated using a range of case examples of studies around pregnancy.

Pharmacokinetic optimization of antiretroviral therapy in pregnancy

Antiretroviral therapy suppresses replication of HIV allowing restoration and/or preservation of the immune system. Providing combination antiretroviral therapy during pregnancy can treat maternal HIV infection and/or reduce perinatal HIV transmission. However, providing treatment to pregnant women is challenging due to physiological changes that can alter antiretroviral pharmacokinetics. Suboptimal drug exposure can result in HIV RNA rebound, the selection of resistant virus or an increased risk of HIV-1 transmission to the infant. Increased drug exposure can produce unwarranted maternal adverse effects and/or fetal toxicity. Subsequently, dose adjustments may be necessary during pregnancy to achieve comparable antiretroviral exposure to non-pregnant adults. For several antiretrovirals, systemic exposure is decreased during the last trimester of pregnancy. By 6-12 weeks postpartum, concentrations return to those prior to pregnancy. Also, the extent of antiretroviral placental transfer to the fetus and degree of antiretroviral excretion into breast milk varies within, and between, antiretroviral drug classes. It is necessary to consider the pharmacological characteristics of each antiretroviral when optimizing combination therapy during pregnancy to treat maternal HIV infection and prevent perinatal HIV transmission.

Clinical interventions for women with schizophrenia: pregnancy

OBJECTIVE

A comprehensive treatment program for schizophrenia needs to include services to women of childbearing age that address contraception, pregnancy, and postpartum issues, as well as safe and effective parenting. To update knowledge in these areas, a summary of the recent qualitative and quantitative literature was undertaken.

METHOD

The search terms 'sexuality,''contraception,''pregnancy,''postpartum,''custody,' and 'parenting' were entered into PubMed, PsycINFO, and SOCINDEX along with the terms 'schizophrenia' and 'antipsychotic.' Publications in English for all years subsequent to 2000 were retrieved and their reference lists further searched in an attempt to arrive at a distillation of useful clinical recommendations.

RESULTS

The main recommendations to care providers are as follows: take a sexual history and initiate discussion about intimate relationships and contraception with all women diagnosed with schizophrenia. During pregnancy, adjust antipsychotic dose to clinical status, link the patient with prenatal care services, and help her prepare for childbirth. There are pros and cons to breastfeeding while on medication, and these need thorough discussion. During the postpartum period, mental health home visits should be provided. Parenting support is critical.

CONCLUSION

The comprehensive treatment of schizophrenia in women means remembering that all women of childbearing age are potential new mothers.

Atazanavir pharmacokinetics, efficacy and safety in pregnancy: a systematic review

BACKGROUND

For some antiretroviral therapies, drug concentrations are reduced during pregnancy, potentially compromising effective virological suppression.

METHODS

Data on atazanavir boosted with ritonavir in pregnancy are reviewed.

RESULTS

With standard atazanavir/ritonavir 300/100 mg once-daily dosing: atazanavir area-under-the-concentration-time curves were reduced during pregnancy in most studies, but overall interpretation differed according to the data used for comparison; atazanavir concentration 24 h post-dose was maintained >150 ng/ml in 97.6% of women; no instance of mother-to-child transmission occurred in treatment-adherent mothers; and infant hyperbilirubinaemia was not elevated beyond levels expected in the neonatal period.

CONCLUSIONS

With concurrent medications that reduce atazanavir drug concentrations, optimal therapy during pregnancy may require once-daily atazanavir/ritonavir 400/100 mg; however, using this dose during the third trimester doubled maternal grade 3-4 hyperbilirubinaemia rates.

Gestational age-dependent changes in gene expression of metabolic enzymes and transporters in pregnant mice

Pregnancy-induced changes in drug pharmacokinetics can be explained by changes in expression of drug-metabolizing enzymes and transporters and/or normal physiology. In this study, we determined gestational age-dependent expression profiles for all metabolic enzyme and transporter genes in the maternal liver, kidney, small intestine, and placenta of pregnant mice by microarray analysis. We specifically examined the expression of genes important for xenobiotic, bile acid, and steroid hormone metabolism and disposition, namely, cytochrome P450s (Cyp), UDP-glucuronosyltranserases (Ugt), sulfotransferases (Sult), and ATP-binding cassette (Abc), solute carrier (Slc), and solute carrier organic anion (Slco) transporters. Few Ugt and Sult genes were affected by pregnancy. Cyp17a1 expression in the maternal liver increased 3- to 10-fold during pregnancy, which was the largest observed change in the maternal tissues. Cyp1a2, most Cyp2 isoforms, Cyp3a11, and Cyp3a13 expression in the liver decreased on gestation days (gd) 15 and 19 compared with nonpregnant controls (gd 0). In contrast, Cyp2d40, Cyp3a16, Cyp3a41a, Cyp3a41b, and Cyp3a44 in the liver were induced throughout pregnancy. In the placenta, Cyp expression on gd 10 and 15 was upregulated compared with gd 19. Notable changes were also observed in Abc and Slc transporters. Abcc3 expression in the liver and Abcb1a, Abcc4, and Slco4c1 expression in the kidney were downregulated on gd 15 and 19. In the placenta, Slc22a3 (Oct3) expression on gd 10 was 90% lower than that on gd 15 and 19. This study demonstrates important gestational age-dependent expression of metabolic enzyme and transporter genes, which may have mechanistic relevance to drug disposition in human pregnancy.

Pharmacotherapy in pregnancy; effect of ABC and SLC transporters on drug transport across the placenta and fetal drug exposure

Pharmacotherapy during pregnancy is often inevitable for medical treatment of the mother, the fetus or both. The knowledge of drug transport across placenta is, therefore, an important topic to bear in mind when deciding treatment in pregnant women. Several drug transporters of the ABC and SLC families have been discovered in the placenta, such as P-glycoprotein, breast cancer resistance protein, or organic anion/cation transporters. It is thus evident that the passage of drugs across the placenta can no longer be predicted simply on the basis of their physical-chemical properties. Functional expression of placental drug transporters in the trophoblast and the possibility of drug-drug interactions must be considered to optimize pharmacotherapy during pregnancy. In this review we summarize current knowledge on the expression and function of ABC and SLC transporters in the trophoblast. Furthermore, we put this data into context with medical conditions that require maternal and/or fetal treatment during pregnancy, such as gestational diabetes, HIV infection, fetal arrhythmias and epilepsy. Proper understanding of the role of placental transporters should be of great interest not only to clinicians but also to pharmaceutical industry for future drug design and development to control the degree of fetal exposure.

The impact of Caesarean delivery on paracetamol and ketorolac pharmacokinetics: a paired analysis

Pharmacokinetics is a first, but essential step to improve population-tailored postoperative analgesia, also after Caesarean delivery. We therefore aimed to quantify the impact of caesarean delivery on the pharmacokinetics of intravenous (iv) paracetamol (2 g, single dose) and iv ketorolac tromethamine (30 mg, single dose) in 2 cohorts eachof 8 women at caesarean delivery and to compare these findings with postpartum to quantify intrapatient changes. We documented a higher median paracetamol clearance at delivery when compared to 10–15 weeks postpartum (11.7 to 6.4 L/h·m², P < 0.01), even after correction for weight-related changes. Similar conclusions were drawn for ketorolac: median clearance was higher at delivery with a subsequent decrease (2.03 to 1.43 L/h·m², P < 0.05) in postpartum (17–23 weeks). These differences likely reflect pregnancy- and caesarean-delivery-related changes in drug disposition. Moreover, postpartum paracetamol clearance was significantly lower when compared to estimates published in healthy young volunteers (6.4  versus  9.6 L/h·m²), while this was not the case for ketorolac (1.43  versus  1.48 L/h·m²). This suggests that postpartum is another specific status in young women that merits focused, compound-specific pharmacokinetic evaluation.