Mechanisms of altered hepatic drug disposition during pregnancy: small molecules

INTRODUCTION

Pregnancy alters the systemic exposure and clearance of many hepatically cleared drugs that are commonly used by obstetric patients. Understanding the molecular mechanisms underlying the changes in factors that affect hepatic drug clearance (blood flow, protein binding, and intrinsic clearance) is essential to more precisely predict systemic drug exposure and dose requirements in obstetric patients.

AREAS COVERED

This review (1) summarizes the anatomic, physiologic, and biochemical changes in maternal hepatic, cardiovascular, endocrine, and renal systems relevant to hepatic drug clearance and (2) reviews the molecular mechanisms underlying the altered hepatic metabolism and intrinsic clearance of drugs during pregnancy via a comprehensive PubMed search. It also identifies knowledge gaps in the molecular mechanisms and factors that modulate hepatic drug clearance during pregnancy.

EXPERT OPINION

Pharmacokinetic studies have shown that pregnancy alters systemic exposure, protein binding, and clearance of many drugs during gestation in part due to pregnancy-associated decreases in plasma albumin, increases in organ blood flow, and changes in the activity of drug-metabolizing enzymes (DMEs) and transporters. The changes in the activity of certain DMEs and transporters during pregnancy are likely driven by hormonal-changes that inhibit their activity or alter the expression of these proteins through activation of transcription factors.

Changes in S-Citalopram Plasma Concentrations Across Pregnancy and Postpartum

Major depressive disorder is a common disorder in pregnancy. Although citalopram/escitalopram is the second most frequently prescribed antidepressant for pregnant people, information about its pharmacokinetics in pregnancy is limited. We investigated plasma (S)-citalopram concentration to dose (C/D) ratios across pregnancy and postpartum and the effect of pharmacogenetics on its elimination. This prospective observational cohort study enrolled 30 participants with a singleton pregnancy who chose to continue citalopram/escitalopram during pregnancy for a prior diagnosis of major depression. Monthly blood samples were obtained 24 hours post-dose across pregnancy and twice postpartum for measurement of plasma citalopram, desmethylcitalopram, and didesmethylcitalopram enantiomer concentrations. Compared with the 36-week reference, (S)-citalopram C/D ratios were not significantly different throughout pregnancy. However, the mean (S)-citalopram C/D ratio was elevated by 63% (P < 0.001) 6 to 8 weeks after delivery before it decreased to a mean C/D ratio in the later post-birth period that was marginally different than at 36 weeks (1.20 ± 0.64 vs. 0.92 ± 0.46, respectively; P = 0.06). Analyzing the results by cytochrome P 450 (CYP) 2C19 phenotype, the mean late postpartum (S)-citalopram concentration to dose ratio in intermediate metabolizers was approximately twice that in extensive, rapid, or ultrarapid metabolizers. However, at the 36-week reference point, the mean concentration to dose ratio in pregnant CYP2C19 intermediate metabolizers was 35.7% lower than the distant postpartum ratio, while the ratios in extensive and rapid/ultrarapid metabolizers were 15.4% and 18.5% lower, respectively. Without dose adjustment, people with intermediate or poor CYP2C19 activity may be at risk for subtherapeutic S-citalopram concentrations during pregnancy.

Safety in treatment: Classical pharmacotherapeutics and new avenues for addressing maternal depression and anxiety during pregnancy

We aimed to review clinical research on the safety profiles of antidepressant drugs and associations with maternal depression and neonatal outcomes. We focused on neuroendocrine changes during pregnancy and their effects on antidepressant pharmacokinetics. Pregnancy-induced alterations in drug disposition and metabolism impacting mothers and their fetuses are discussed. We considered evidence for the risks of antidepressant use during pregnancy. Teratogenicity associated with ongoing treatment, new prescriptions during pregnancy, or pausing medication while pregnant was examined. The Food and Drug Administration advises caution regarding prenatal exposure to most drugs, including antidepressants, largely owing to a dearth of safety studies caused by the common exclusion of pregnant individuals in clinical trials. We contrasted findings on antidepressant use with the lack of treatment where detrimental effects to mothers and children are well researched. Overall, drug classes such as selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors appear to have limited adverse effects on fetal health and child development. In the face of an increasing prevalence of major mood and anxiety disorders, we assert that individuals should be counseled before and during pregnancy about the risks and benefits of antidepressant treatment given that withholding treatment has possible negative outcomes. Moreover, newer therapeutics, such as ketamine and κ-opioid receptor antagonists, warrant further investigation for use during pregnancy. SIGNIFICANCE STATEMENT: The safety of antidepressant use during pregnancy remains controversial owing to an incomplete understanding of how drug exposure affects fetal development, brain maturation, and behavior in offspring. This leaves pregnant people especially vulnerable, as pregnancy can be a highly stressful experience for many individuals, with stress being the biggest known risk factor for developing a mood or anxiety disorder. This review focuses on perinatal pharmacotherapy for treating mood and anxiety disorders, highlighting the current knowledge and gaps in our understanding of consequences of treatment.

Concentrations of Fluoxetine Enantiomers Decline During Pregnancy and Increase After Birth

RATIONALE

Few studies of the effect of the dynamic physiologic changes during pregnancy on plasma concentrations of fluoxetine (FLX) have been published.

OBJECTIVES

We determined the change in concentration to dose (C/D) ratios of R- and S-FLX and R- and S-norfluoxetine monthly during pregnancy and postpartum, assessed their relationships to cytochrome P450 (CYP) 2D6 and CYP2C9 metabolizer phenotypes, and evaluated the course of their depressive and anxiety symptoms.

METHODS

In this observational study, 10 FLX-treated pregnant individuals provided blood samples at steady state every 4 weeks during pregnancy and once postpartum for measurement of plasma FLX and norfluoxetine enantiomer concentrations. Participants were genotyped for variants in CYP2C9 and CYP2D6 using commercial assays with Taqman probes. At each assessment, depressive and anxiety symptoms were quantified.

RESULTS

The C/D ratios of all FLX and norfluoxetine enantiomers, and the active moiety, decreased steadily through pregnancy and rose after birth. In the final trimester, the mean C/D ratio of the active moiety was 24.9% lower compared with the mean nonpregnant, 12-week postpartum C/D ratio. One individual with CYP2D6 ultrarapid metabolizer status was prescribed the highest FLX dose among participants. In these treated individuals, the mean depressive and anxiety symptoms remained in the mild range across the perinatal period.

CONCLUSIONS

These data do not support a recommendation for routine plasma concentration monitoring or CYP2D6 pharmacogenetic testing for pregnant people treated with FLX; however, monitoring for symptom relapse is recommended because of declining plasma drug concentrations.

Impact of CYP2D6 Genotype on Paroxetine Serum Concentration

BACKGROUND

Paroxetine is a selective serotonin reuptake inhibitor metabolized by cytochrome P450 (CYP)2D6. Only small-scale studies have reported the impact of CYP2D6 genotype on paroxetine exposure, and international guidelines differ in their recommendations on whether paroxetine should be administered according to CYP2D6 genotype. To clarify this issue, the aim of the present study was to investigate the impact of CYP2D6 genotype on paroxetine serum concentration in a large population of patients after adjusting for CYP2C19 genotype, age, and sex.

METHODS

Patients from a therapeutic drug monitoring database with records on their paroxetine serum concentrations and CYP2D6 and CYP2C19 genotyping between 2010 and 2021 were included in the study. The impact of CYP2D6 and CYP2C19 genotypes, age, and sex on the paroxetine concentration-to-dose (C/D) ratio was investigated by multiple linear regression analysis. Patients treated with relevant CYP inhibitors or inducers were excluded.

RESULTS

In total, 304 patients were included in the study: 17 CYP2D6 poor metabolizers (PMs), 114 intermediate metabolizers (IMs), 168 extensive metabolizers (EMs), and 5 ultrarapid metabolizers. Multiple linear regression analysis showed that CYP2D6 IMs and PMs had 2.2-fold and 3.8-fold higher paroxetine C/D-ratios than extensive metabolizers, respectively ( P < 0.001). Patients who were CYP2C19 IMs (n = 70) or PMs (n = 13) had 1.6-fold higher paroxetine C/D ratio than extensive metabolizers ( P = 0.04). An age ≥65 years was associated with a 2.9-fold increased C/D ratio ( P < 0.001), whereas sex was not significantly associated with paroxetine exposure.

CONCLUSIONS

The present study showed that CYP2D6 genotype is of significant importance for paroxetine dose adjustments. For CYP2D6 PMs, 25% of the regular paroxetine starting dose may be sufficient, whereas CYP2D6 IMs could receive 50% of the regular dosage. This well-powered study shows that the guidelines should consider the importance of CYP2D6 genotype for personalized dosing of paroxetine.

Design Considerations for Pharmacokinetic Studies During Pregnancy

Most of the interventions performed by obstetric providers involve the administration of drugs. Pregnant patients are pharmacologically and physiologically different from nonpregnant young adults. Therefore, dosages that are effective and safe for the general public may be inadequate or unsafe for the pregnant patient and her fetus. Establishing dosing regimens appropriate for pregnancy requires evidence generated from pharmacokinetic studies performed in pregnant people. However, performing these studies during pregnancy often requires special design considerations, evaluations of both maternal and fetal exposures, and recognition that pregnancy is a dynamic process that changes as gestational age advances. In this article, we address design challenges unique to pregnancy and discuss options for investigators, including timing of drug sampling during pregnancy, appropriate selection of control groups, pros and cons of dedicated and nested pharmacokinetic studies, single-dose and multiple-dose analyses, dose selection strategies, and the importance of integrating pharmacodynamic changes into these protocols. Examples of completed pharmacokinetic studies in pregnancy are provided for illustration.

Pharmacokinetics of Antidepressants in Pregnancy

Depression is common in pregnant women. However, the rate of antidepressant treatment in pregnancy is significantly lower than in nonpregnant women. Although some antidepressants may cause potential risks to the fetus, not treating or withdrawing the treatment is associated with relapsing and adverse pregnancy outcomes such as preterm birth. Pregnancy-associated physiologic changes can alter pharmacokinetics (PK) and may impact dosing requirements during pregnancy. However, pregnant women are largely excluded from PK studies. Dose extrapolation from the nonpregnant population could lead to ineffective doses or increased risk of adverse events. To better understand PK changes during pregnancy and guide dosing decisions, we conducted a literature review to catalog PK studies of antidepressants in pregnancy, with a focus on maternal PK differences from the nonpregnant population and fetal exposure. We identified 40 studies on 15 drugs, with most data from patients taking selective serotonin reuptake inhibitors and venlafaxine. Most of the studies have relatively poor quality, with small sample sizes, reporting concentrations at delivery only, a large amount of missing data, and not including times and adequate dose information. Only four studies collected multiple samples following a dose and reported PK parameters. In general, there are limited data available regarding PK of antidepressants in pregnancy and deficiencies in data reporting. Future studies should provide accurate information on drug dosing and timing of dose, PK sample collection, and individual-level PK data.

Pharmacokinetic Evaluation in Pregnancy-Current Status and Future Considerations: Workshop Summary

As pregnant individuals have traditionally been excluded from clinical trials, there is a gap in knowledge at the time of drug approval regarding safety, efficacy, and appropriate dosing for most prescription medications used during pregnancy. Physiologic changes in pregnancy can result in changes in pharmacokinetics that can impact safety or efficacy. This highlights the need to foster further research and collection of pharmacokinetic data in pregnancy to ensure appropriate drug dosing in pregnant individuals. Therefore, the US Food and Drug Administration and the University of Maryland Center of Excellence in Regulatory Science and Innovation hosted a workshop on May 16 and 17, 2022, titled "Pharmacokinetic Evaluation in Pregnancy." This is a summary of the workshop proceedings.

Impact of Pregnancy and Vitamin A Supplementation on CYP2D6 Activity

The mechanism of cytochrome P450 2D6 (CYP2D6) induction during pregnancy has not been evaluated in humans. This study assessed the changes in CYP2D6 and CYP3A activities during pregnancy and postpartum, and the effect of vitamin A administration on CYP2D6 activity. Forty-seven pregnant CYP2D6 extensive metabolizers (with CYP2D6 activity scores of 1 to 2) received dextromethorphan (DM) 30 mg orally as a single dose during 3 study windows (at 25 to 28 weeks of gestation, study day 1; at 28 to 32 weeks of gestation, study day 2; and at ≥3 months postpartum, study day 3). Participants were randomly assigned to groups with no supplemental vitamin A (control) or with supplemental vitamin A (10 000 IU/day orally for 3 to 4 weeks) after study day 1. Concentrations of DM and its metabolites, dextrorphan (DX) and 3-hydroxymorphinan (3HM), were determined from a 2-hour post-dose plasma sample and cumulative 4-hour urine sample using liquid chromatography-mass spectrometry. Change in CYP2D6 activity was assessed using DX/DM plasma and urine metabolic ratios. The activity change in CYP3A was also assessed using the 3HM/DM urine metabolic ratio. The DX/DM urine ratio was significantly higher (43%) in pregnancy compared with postpartum (P = .03), indicating increased CYP2D6 activity. The DX/DM plasma ratio was substantially higher in the participants, with an activity score of 1.0 during pregnancy (P = .04) compared with postpartum. The 3HM/DM urinary ratio was significantly higher (92%) during pregnancy, reflecting increased CYP3A activity (P = .02). Vitamin A supplementation did not change CYP2D6 activity during pregnancy; however, plasma all-trans retinoic acid (atRA) concentrations were positively correlated with increased CYP2D6 activity during pregnancy and postpartum. Further research is needed to elucidate the mechanisms of increased CYP2D6 activity during pregnancy.

Principles of Obstetric Pharmacology: Maternal Physiologic and Hepatic Metabolism Changes

Since the recognition of pregnancy as a special pharmacokinetic population in the late 1990s, investigations have expanded our understanding of obstetric pharmacology. Many of the basic physiologic changes that occur during pregnancy impact on drug absorption, distribution, or clearance. Activities of hepatic metabolizing enzymes are variably altered by pregnancy, resulting in concentrations sufficiently different for some drugs that efficacy or toxicity may be affected. Understanding these unique pharmacologic changes will better inform our use of medications for our pregnant patients.

Considerations for the Use of Long-Acting and Extended-Release Agents During Pregnancy and Lactation

Long-acting agents hold significant promise for treating and preventing common illnesses, including infections. Pharmacokinetic and safety data during pregnancy and lactation are often unavailable for new drugs; these data are vital to facilitate optimal drug use by pregnant and lactating women and women who may conceive. In this commentary, we summarize the circumstances in which pregnant and lactating women are likely to use and benefit from long-acting agents. We focus on long-acting formulations of small molecules (rather than biologics such as monoclonal antibodies) and on several infections of global importance (human immunodeficiency virus, tuberculosis, malaria, and hepatitis C). We discuss pregnancy pharmacokinetic/pharmacodynamic and potential safety and efficacy considerations pertaining to the use of long-acting agents in pregnancy and lactation. Finally, we summarize existing preclinical and pregnancy pharmacokinetic data that are available (or expected in the near future) for several agents that are under development or approved, and how key research gaps may be addressed.

[Impact of pregnancy on drug pharmacokinetics: What implication in clinical practice?]

Physiological changes that occur during pregnancy in the maternal body can lead to alterations in the response to drugs in the mother. Pregnancy modifies the volume of distribution of drugs, their binding to plasma proteins, the activity of their metabolizing enzymes, and their elimination. However, to date, due to the dynamic and complex processes involved, adjustments to the dosage regimen during pregnancy remain impossible to standardize. Knowledge of these modifications will help to better understand the possible loss of drug efficacy during pregnancy, as well as anticipating the clinical and plasma monitoring of drugs with a low therapeutic margin.

A cross-sectional study of the relationship between CYP2D6 and CYP2C19 variations and depression symptoms, for women taking SSRIs during pregnancy

Depression during pregnancy affects 10-15% of women, and 5% of women take antidepressants during pregnancy. Clinical guidelines provide recommendations for selective serotonin reuptake inhibitor (SSRI) drug choice and dose based on CYP2D6 and CYP2C19 genotype; however, they are based on evidence from non-pregnant cohorts. This study aimed to test the hypothesis that women with function-altering variants (increased, decreased, or no function) in these pharmacogenes, taking SSRIs prenatally, would have more depression symptoms than women whose pharmacogenetic variants are associated with normal SSRI metabolism. Comprehensive CYP2D6 and CYP2C19 genotyping using a range of methods, including gene copy number analysis, was performed as secondary analyses on two longitudinal cohorts of pregnant women (N = 83) taking the SSRIs paroxetine, citalopram, escitalopram, or sertraline. The Kruskal-Wallis test compared mean depression scores across four predicted metabolizer groups: poor (n = 5), intermediate (n = 10), normal (n = 53), and ultrarapid (n = 15). There were no significant differences between mean depression scores across the four metabolizer groups (H(3) = .73, p = .87, eta-squared = .029, epsilon-squared = .0089). This is the first study of the relationship in pregnancy between CYP2C19 pharmacogenetic variations and depression symptoms in the context of SSRI use. Findings from this initial study do not support the clinical use of pharmacogenetic testing for SSRI use during the second or third trimesters of pregnancy, but these findings should be confirmed in larger cohorts. There is an urgent need for further research to clarify the utility of pharmacogenetic testing for pregnant women, especially as companies offering direct-to-consumer genetic testing expand their marketing efforts.

Selective Serotonin Reuptake Inhibitor Pharmacokinetics During Pregnancy: Clinical and Research Implications

Pregnancy and associated physiologic changes affect the pharmacokinetics of many medications, including selective serotonin reuptake inhibitors—the first-line pharmacologic interventions for depressive and anxiety disorders. During pregnancy, SSRIs exhibit extensive pharmacokinetic variability that may influence their tolerability and efficacy. Specifically, compared to non-pregnant women, the activity of cytochrome P450 (CYP) enzymes that metabolize SSRIs drastically changes (e.g., decreased CYP2C19 activity and increased CYP2D6 activity). This perspective examines the impact of pharmacokinetic genes—related to CYP activity on SSRI pharmacokinetics during pregnancy. Through a simulation-based approach, plasma concentrations for SSRIs metabolized primarily by CYP2C19 (e.g., escitalopram) and CYP2D6 (e.g., fluoxetine) are examined and the implications for dosing and future research are discussed.

The application of precision dosing in the use of sertraline throughout pregnancy for poor and ultrarapid metabolizer CYP 2C19 subjects: A virtual clinical trial pharmacokinetics study

Sertraline is known to undergo changes in pharmacokinetics during pregnancy. CYP 2C19 has been implicated in the interindividual variation in clinical effect associated with sertraline activity. However, knowledge of suitable dose titrations during pregnancy and within CYP 2C19 phenotypes is lacking. A pharmacokinetic modeling virtual clinical trials approach was implemented to: (i) assess gestational changes in sertraline trough plasma concentrations for CYP 2C19 phenotypes, and (ii) identify appropriate dose titration strategies to stabilize sertraline levels within a defined therapeutic range throughout gestation. Sertraline trough plasma concentrations decreased throughout gestation, with maternal volume expansion and reduction in plasma albumin being identified as possible causative reasons. All CYP 2C19 phenotypes required a dose increase throughout gestation. For extensive metabolizer (EM) and ultrarapid metabolizer (UM) phenotypes, doses of 100-150 mg daily are required throughout gestation. For poor metabolizers (PM), 50 mg daily during trimester 1 followed by a dose of 100 mg daily in trimesters 2 and 3 are required.

Association of CYP2C19 and CYP2D6 Poor and Intermediate Metabolizer Status With Antidepressant and Antipsychotic Exposure: A Systematic Review and Meta-analysis

IMPORTANCE

Precise estimation of the drug metabolism capacity for individual patients is crucial for adequate dose personalization.

OBJECTIVE

To quantify the difference in the antipsychotic and antidepressant exposure among patients with genetically associated CYP2C19 and CYP2D6 poor (PM), intermediate (IM), and normal (NM) metabolizers.

DATA SOURCES

PubMed, Clinicaltrialsregister.eu, ClinicalTrials.gov, International Clinical Trials Registry Platform, and CENTRAL databases were screened for studies from January 1, 1990, to June 30, 2020, with no language restrictions.

STUDY SELECTION

Two independent reviewers performed study screening and assessed the following inclusion criteria: (1) appropriate CYP2C19 or CYP2D6 genotyping was performed, (2) genotype-based classification into CYP2C19 or CYP2D6 NM, IM, and PM categories was possible, and (3) 3 patients per metabolizer category were available.

DATA EXTRACTION AND SYNTHESIS

The Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines were followed for extracting data and quality, validity, and risk of bias assessments. A fixed-effects model was used for pooling the effect sizes of the included studies.

MAIN OUTCOMES AND MEASURES

Drug exposure was measured as (1) dose-normalized area under the plasma level (time) curve, (2) dose-normalized steady-state plasma level, or (3) reciprocal apparent total drug clearance. The ratio of means (RoM) was calculated by dividing the mean drug exposure for PM, IM, or pooled PM plus IM categories by the mean drug exposure for the NM category.

RESULTS

Based on the data derived from 94 unique studies and 8379 unique individuals, the most profound differences were observed in the patients treated with aripiprazole (CYP2D6 PM plus IM vs NM RoM, 1.48; 95% CI, 1.41-1.57; 12 studies; 1038 patients), haloperidol lactate (CYP2D6 PM vs NM RoM, 1.68; 95% CI, 1.40-2.02; 9 studies; 423 patients), risperidone (CYP2D6 PM plus IM vs NM RoM, 1.36; 95% CI, 1.28-1.44; 23 studies; 1492 patients), escitalopram oxalate (CYP2C19 PM vs NM, RoM, 2.63; 95% CI, 2.40-2.89; 4 studies; 1262 patients), and sertraline hydrochloride (CYP2C19 IM vs NM RoM, 1.38; 95% CI, 1.27-1.51; 3 studies; 917 patients). Exposure differences were also observed for clozapine, quetiapine fumarate, amitriptyline hydrochloride, mirtazapine, nortriptyline hydrochloride, fluoxetine hydrochloride, fluvoxamine maleate, paroxetine hydrochloride, and venlafaxine hydrochloride; however, these differences were marginal, ambiguous, or based on less than 3 independent studies.

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, the association between CYP2C19/CYP2D6 genotype and drug levels of several psychiatric drugs was quantified with sufficient precision as to be useful as a scientific foundation for CYP2D6/CYP2C19 genotype-based dosing recommendations.

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.

Do Maternal Pharmacogenetics Impact the Neonatal Abstinence Syndrome Following In Utero Exposure to Antidepressant Medications?

OBJECTIVE

Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are the most commonly used medications for mood and anxiety disorders in women. Many women need to continue or initiate these medications during pregnancy, but there is concern about potential withdrawal effects in the newborn, referred to as neonatal abstinence syndrome (NAS). The reason why some infants remain asymptomatic while others are affected has not been elucidated. The objective of this study was to examine whether genetic differences in maternal drug metabolism influence the incidence of NAS.

METHODS

Women who took Selective serotonin reuptake inhibitors s/SNRIs during pregnancy were recruited from obstetrical clinics. DNA was extracted from saliva samples for genetic analyses of cytochrome P450 (CYP) enzyme polymorphisms. Delivery and NAS data were collected from electronic medical records.

RESULTS

Ninety-five women participated. The overall NAS rate was 16.2%. Mild NAS was seen in 13.8% of neonates and severe NAS, in 2%. One-quarter (25%) of the neonates with mild withdrawal symptoms were born to mothers with polymorphisms associated with slower metabolism of their particular antidepressant, but this association was not statistically significant.

CONCLUSION

Importantly, the overall rate of NAS in our study was lower than previously reported. Maternal CYP polymorphisms did not affect the rate of NAS in neonates exposed to SSRIs/SNRIs in utero. This study lends added assurance to patients requiring SSRIs or SNRIs during pregnancy.

Phenoconversion of Cytochrome P450 Metabolism: A Systematic Review

Phenoconversion is the mismatch between the individual’s genotype-based prediction of drug metabolism and the true capacity to metabolize drugs due to nongenetic factors. While the concept of phenoconversion has been described in narrative reviews, no systematic review is available. A systematic review was conducted to investigate factors contributing to phenoconversion and the impact on cytochrome P450 metabolism. Twenty-seven studies met the inclusion criteria and were incorporated in this review, of which 14 demonstrate phenoconversion for a specific genotype group. Phenoconversion into a lower metabolizer phenotype was reported for concomitant use of CYP450-inhibiting drugs, increasing age, cancer, and inflammation. Phenoconversion into a higher metabolizer phenotype was reported for concomitant use of CYP450 inducers and smoking. Moreover, alcohol, pregnancy, and vitamin D exposure are factors where study data suggested phenoconversion. The studies reported genotype–phenotype discrepancies, but the impact of phenoconversion on the effectiveness and toxicity in the clinical setting remains unclear. In conclusion, phenoconversion is caused by both extrinsic factors and patient- and disease-related factors. The mechanism(s) behind and the extent to which CYP450 metabolism is affected remain unexplored. If studied more comprehensively, accounting for phenoconversion may help to improve our ability to predict the individual CYP450 metabolism and personalize drug treatment.

Drug dosing during pregnancy-opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed.

Precision dosing-based optimisation of paroxetine during pregnancy for poor and ultrarapid CYP2D6 metabolisers: a virtual clinical trial pharmacokinetics study

Objective

Paroxetine has been demonstrated to undergo gestation-related reductions in plasma concentrations, to an extent which is dictated by the polymorphic state of CYP 2D6. However, knowledge of appropriate dose titrations is lacking.

Methods

A pharmacokinetic modelling approach was applied to examine gestational changes in trough plasma concentrations for CYP 2D6 phenotypes, followed by necessary dose adjustment strategies to maintain paroxetine levels within a therapeutic range of 20–60 ng/ml.

Key findings

A decrease in trough plasma concentrations was simulated throughout gestation for all phenotypes. A significant number of ultrarapid (UM) phenotype subjects possessed trough levels below 20 ng/ml (73–76%) compared to extensive metabolisers (EM) (51–53%).

Conclusions

For all phenotypes studied, there was a requirement for daily doses in excess of the standard 20 mg dose throughout gestation. For EM, a dose of 30 mg daily in trimester 1 followed by 40 mg daily in trimesters 2 and 3 is suggested to be optimal. For poor metabolisers (PM), a 20 mg daily dose in trimester 1 followed by 30 mg daily in trimesters 2 and 3 is suggested to be optimal. For UM, a 40 mg daily dose throughout gestation is suggested to be optimal.

The impact of pregnancy on the pharmacokinetics of antidepressants: a systematic critical review and meta-analysis

Introduction: Pregnancy-related physiological changes exert a crucial impact on the pharmacokinetics of antidepressants; however, the current evidence presents inconsistencies. A clearer understanding of pregnancy-related effects on antidepressant disposition may facilitate the development of guidelines for appropriate dose adjustments during the course of pregnancy based on therapeutic drug monitoring.Areas covered: We systematically reviewed studies comparing antidepressant levels in the same individuals during pregnant and non-pregnant states. Using dose-adjusted plasma concentration measurements, we estimated alteration ratios between the 3rd trimester and baseline (before or after pregnancy). Additionally, we performed a meta-analysis for changes in dose-adjusted concentrations to estimate mean differences.Expert opinion: Data for several antidepressants display clear alteration patterns during pregnancy. On the basis of the alteration ratios trimipramine, fluvoxamine, and nortriptyline show a prominent decrease in dose-adjusted levels, especially in the 3rd trimester. Clomipramine, imipramine, citalopram, and paroxetine show smaller decreases in dose-adjusted concentrations in the third trimester. For escitalopram, venlafaxine and fluoxetine, changes are considered negligible. For sertraline, there was a tendency toward increased dose-adjusted concentrations in pregnancy. Available evidence suffers from major limitations and factors affecting pharmacokinetics have been insufficiently addressed. Further research is required to promote knowledge on pregnancy effects on antidepressant pharmacokinetics.

A common clinical conundrum: Antidepressant treatment of depression in pregnant women

Depression during pregnancy is associated with adverse maternal, pregnancy, and infant outcomes. Treatment during pregnancy requires a balanced discussion of the risks of both drug exposure and untreated depression. An updated review of the epidemiology, outcomes, and management of maternal depression is presented. Adverse outcomes are associated with both maternal depression and antidepressants. Research gaps include data on the longitudinal developmental trajectory of offspring exposed to antidepressants compared to depression, with assessment of in utero symptom exposure and environmental exposures. Additionally, neonatal syndrome associated with antidepressant use during pregnancy has no consensus definition or mechanistic explanation. With sophisticated large-scale epidemiologic studies, there has been progress in distinguishing the impact of depression processes from medication used for treatment. Optimal treatment of perinatal depression includes close symptom monitoring and medication adjustments to maintain symptom remission. This evolving field requires frequent consultation with reproductive data sources included in this article.

Drugs in pregnancy: Pharmacologic and physiologic changes that affect clinical care

Pharmacologic interventions play a major role in obstetrical care throughout pregnancy, labor and delivery and the postpartum. Traditionally, obstetrical providers have utilized standard dosing regimens developed for non-obstetrical indications based on pharmacokinetic knowledge from studies in men or non-pregnant women. With the recognition of pregnancy as a special pharmacokinetic population in the late 1990s, investigators have begun to study drug disposition in this unique patient dyad. Many of the basic physiologic changes that occur during pregnancy have significant impact on drug absorption, distribution and clearance. Activity of Phase I and Phase II drug metabolizing enzymes are differentially altered by pregnancy, resulting in drug concentrations sufficiently different for some medications that efficacy or toxicity is affected. Placental transporters play a major dynamic role in determining fetal drug exposure. In the past two decades, we have begun to expand our understanding of obstetrical pharmacology; however, to truly optimize pharmacologic care of our pregnant patients and their developing fetus, additional research is critically needed.

Psychotropic drug use in perinatal women with bipolar disorder

Optimal dose management of psychotropic drugs during the perinatal period reduces the risk for recurrence of mood episodes in women with Bipolar Disorder. Physiological changes during pregnancy are associated with decreases in the plasma concentrations of the majority of mood stabilizing medications. Regular symptom and drug concentration monitoring for lithium and anticonvulsants with reflexive dose adjustment improves the probability of sustained symptom remission across pregnancy. The elimination clearance trajectory across pregnancy for psychotropics dictates the frequency of laboratory monitoring and dose adjustment. The literature on the pharmacokinetics of lithium, lamotrigine, carbamazepine and atypical antipsychotics during pregnancy and postpartum are reviewed, recommendations for symptom and laboratory monitoring are proposed and recommendations for dose adjustments are presented.

Pharmacogenomics in pregnancy

Pregnant women frequently take prescription and over the counter medications. The efficacy of medications is affected by the many physiological changes during pregnancy, and these events may be further impacted by genetic factors. Research on pharmacogenomic and pharmacokinetic influences on drug disposition during pregnancy has lagged behind other fields. Clinical investigators have demonstrated altered activity of several drug metabolizing enzymes during pregnancy. Emerging evidence also supports the influence of pharmacogenomic variability in drug response for many important classes of drugs commonly used in pregnancy. Prescribing medications during pregnancy requires an understanding of the substantial dynamic physiologic and metabolic changes that occur during gestation. Pharmacogenomics also contributes to the inter-individual variability in response to many medications, and more research is needed to understand how best to manage drug therapy in pregnant women.

Psychotropic Treatment During Pregnancy: Research Synthesis and Clinical Care Principles

Background: Psychiatric illnesses are common in women of childbearing age. The perinatal period is a particularly high-risk time for depression, bipolar, and anxiety disorders. Methods: The scope of the public health problem of perinatal mental disorders is discussed followed by an examination of the specific research methods utilized for the study of birth and developmental outcomes associated with maternal mental illness and its treatment. The evidence on exposure to common psychotropics during pregnancy and breastfeeding is reviewed. Results: Selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitor medications are not associated with higher rates of birth defects or long-term changes in mental development after adjustment for confounding factors associated with underlying psychiatric illness. Lithium exposure is associated with an increased risk for fetal cardiac malformations, but this risk is lower than previously thought (absolute risk of Ebstein's anomaly 6/1,000). Antipsychotics, other than risperidone and potentially paliperidone, have not been associated with an increase in birth defects; olanzapine and quetiapine have been linked with an elevated risk of gestational diabetes. Due to the dramatic physiological changes of pregnancy and enhanced hepatic metabolism, drug doses may need to be adjusted during pregnancy to sustain efficacy. Untreated maternal psychiatric illness also carries substantial risks for the mother, fetus, infant, and family. Conclusions: The goal of perinatal mental health treatment is to optimally provide pharmacotherapy to mitigate the somatic and psychosocial burdens of maternal psychiatric disorders. Regular symptom monitoring during pregnancy and postpartum and medication dose adjustments to sustain efficacy constitutes good practice.

SSRIs and SNRIs (SRI) in Pregnancy: Effects on the Course of Pregnancy and the Offspring: How Far Are We from Having All the Answers?

Serotonin has important roles in the development of the brain and other organs. Manipulations of synaptic serotonin by drugs such as serotonin reuptake inhibitors (SRI) or serotonin norepinephrine reuptake inhibitors (SNRI) might alter their development and function. Of interest, most studies on the outcome of prenatal exposure to SRI in human have not found significant embryonic or fetal damage, except for a possible, slight increase in cardiac malformations. In up to a third of newborns exposed to SRI, exposure may induce transient neonatal behavioral changes (poor neonatal adaptation) and increased rate of persistent pulmonary hypertension. Prenatal SRI may also cause slight motor delay and language impairment but these are transient. The data on the possible association of prenatal SRIs with autism spectrum disorder (ASD) are inconsistent, and seem to be related to pre-pregnancy treatment or to maternal depression. Prenatal SRIs also appear to affect the hypothalamic hypophyseal adrenal (HPA) axis inducing epigenetic changes, but the long-term consequences of these effects on humans are as yet unknown. SRIs are metabolized in the liver by several cytochrome P450 (CYP) enzymes. Faster metabolism of most SRIs in late pregnancy leads to lower maternal concentrations, and thus potentially to decreased efficacy which is more prominent in women that are rapid metabolizers. Studies suggest that the serotonin transporter SLC6A4 promoter is associated with adverse neonatal outcomes after SRI exposure. Since maternal depression may adversely affect the child's development, one has to consider the risk of SRI discontinuation on the fetus and the child. As with any drug treatment in pregnancy, the benefits to the mother should be considered versus the possible hazards to the developing embryo/fetus.

The dynamic serotonin system of the maternal brain

Many pregnant and postpartum women worldwide suffer from high anxiety and/or depression, which can have detrimental effects on maternal and infant well-being. The first-line pharmacotherapies for prepartum and postpartum affective disorders continue to be the selective serotonin reuptake inhibitors (SSRIs), despite the lack of large well-controlled studies demonstrating their efficacy in reproducing women and the potential for fetal/neonatal exposure to the drugs. Prepartum or postpartum use of SSRIs or other drugs that modulate the brain's serotonin system is also troubling because very little is known about the typical, let alone the atypical, changes that occur in the female central serotonin system across reproduction. We do know from a handful of studies of women and female laboratory rodents that numerous aspects of the central serotonin system are naturally dynamic across reproduction and are also affected by pregnancy stress (a major predisposing factor for maternal psychopathology). Thus, it should not be assumed that the maternal central serotonin system being targeted by SSRIs is identical to non-parous females or males. More information about the normative and stress-derailed changes in the maternal central serotonin system is essential for understanding how serotonin is involved in the etiology of, and the best use of SSRIs for potentially treating, affective disorders in the pregnant and postpartum populations.

Clinical implications of selective serotonin reuptake inhibitors-selective serotonin norepinephrine reuptake inhibitors pharmacogenetics during pregnancy and lactation

Depression occurs during pregnancy in 3.9–12.8% of the women. The different serotonin reuptake inhibitors (SRIs) are metabolized in the liver by CYP450 enzymes. CYP2D6 metabolizes paroxetine, fluoxetine, duloxetine and venlafaxine, while CYP2C19 deactivates citalopram and escitalopram. Polymorphisms in these enzymes change the metabolic clearance and levels of these drugs. Higher metabolism of most SRIs in late pregnancy results in lower maternal levels, which could result in decreased efficacy. Very few studies have addressed the potential interaction between pregnancy-induced increase in 2D6 metabolism and specific genotypes of the women, suggesting that ultra-rapid and extensive metabolizers exhibit lower serum concentrations than the other slower genotypes. Preliminary studies suggest that some genotypes of the serotonin transporter (SLC6A4) promoter are associated and are linked to adverse effects in infants with SRI exposure during pregnancy. Presently, there are no clear clinical implications of SRI pharmacogenetic status in pregnancy and lactation. In late pregnancy, women may exhibit lower steady state concentrations of these drugs, necessitating increased doses but these are presently guided clinically and not through genotyping. Much more work is needed to define whether SRI genotype has clinical implications and predictive value for either mother or offspring.

Selective serotonin reuptake inhibitor use in pregnant women; pharmacogenetics, drug-drug interactions and adverse effects

INTRODUCTION

Possible negative effects of selective serotonin reuptake inhibitors (SSRIs) in pregnancy relate to congenital anomalies, negative perinatal events and neurodevelopmental outcome. Many studies are confounded by the underlying maternal disease and by pharmacogenetic and pharmacokinetic differences of these drugs. Areas covered: The possible interactions of SSRIs and serotonin and norepinephrine reuptake inhibitors with other drugs and the known effects of SSRIs on congenital anomalies, perinatal and neurodevelopmental outcome. Expert opinion: SSRIs should be given with caution when combined with other drugs that are metabolized by cytochrome P450 enzymes. SSRIs apparently increase the rate of severe cardiac malformations, induce neonatal adaptation problems in up to 30% of the offspring, increase the rate of persistent pulmonary hypertension of the newborn and possibly slightly increase the rate of prematurity and low birth weight. Most neurodevelopmental follow up studies did not find significant cognitive impairments except some transient gross motor delay, slight impairment of language abilities and possibly behavioral changes. The literature on the possible association of SSRIs with autism spectrum disorder is inconsistent; if an association exists, it is apparently throughout pregnancy. The risk associated with treatment discontinuation seems to outweigh the risk of treatment, as severe maternal depression may negatively affect the child's development. If needed, treatment should continue in pregnancy with the minimal effective dose.

Association between CYP2D6 Genotypes and the Risk of Antidepressant Discontinuation, Dosage Modification and the Occurrence of Maternal Depression during Pregnancy

Importance: Polymorphic expression of drug metabolizing enzymes affects the metabolism of antidepressants, and thus can contribute to drug response and/or adverse events. Pregnancy itself can affect CYP2D6 activity with profound variations determined by CYP2D6 genotype. Objective: To investigate the association between CYP2D6 genotype and the risk of antidepressant discontinuation, dosage modification, and the occurrence of maternal CYP2D6, Antidepressants, Depression during pregnancy. Setting: Data from the Organization of Teratology Information Specialists (OTIS) Antidepressants in Pregnancy Cohort, 2006-2010, were used. Women were eligible if they were within 14 completed weeks of pregnancy at recruitment and exposed to an antidepressant or having any exposures considered non-teratogenic. Main Outcomes and Measures: Gestational antidepressant usage was self-reported and defined as continuous/discontinued use, and non-use; dosage modification was further documented. Maternal depression and anxiety were measured every trimester using the telephone interviewer-administered Edinburgh Postnatal Depression Scale and the Beck Anxiety Inventory, respectively. Saliva samples were collected and used for CYP2D6 genotype analyses. Logistic regression models were used to calculate crude and adjusted odds ratios (OR) with 95% confidence intervals. Results: A total of 246 pregnant women were included in the study. The majority were normal metabolizers (NM, n = 204, 83%); 3.3% (n = 8) were ultrarapid metabolizers (UM), 5.7% (n = 14) poor metabolizers (PM), and 8.1% (n = 20) intermediate metabolizers (IM). Among study subjects, 139 women were treated with antidepressants at the beginning of pregnancy, and 21 antidepressant users (15%) discontinued therapy during pregnancy. Adjusting for depressive symptoms, and other potential confounders, the risk of discontinuing antidepressants during pregnancy was nearly four times higher in slow metabolizers (poor or intermediate metabolizers) compared to those with a faster metabolism rate (normal or ultrarapid metabolizers), aOR = 3.57 (95% CI: 1.15-11.11). Predicted CYP2D6 metabolizer status did not impact dosage modifications. Compared with slow metabolizers, significantly higher proportion of women in the fast metabolizer group had depressive symptom in the first trimester (19.81 vs. 5.88%, P = 0.049). Almost 21% of treated women remained depressed during pregnancy (14.4% NM-UM; 6.1% PM-IM). Conclusions and Relevance: Prior knowledge of CYP2D6 genotype may help to identify pregnant women at greater risk of antidepressant discontinuation. Twenty percent of women exposed to antidepressants during pregnancy remained depressed, indicating an urgent need for personalized treatment of depression during pregnancy.

Selective serotonin reuptake inhibitors and venlafaxine in pregnancy: Changes in drug disposition

Background

Pregnancy may cause changes in drug disposition. The clinical consequences may be profound and even counterintuitive; in some cases pregnant women may need more than twice their usual drug dose in order to maintain therapeutic drug levels. For antidepressants, evidence on drug disposition in pregnancy is scarce. The aim of this study was to determine the effects of pregnancy on serum levels of selective serotonin reuptake inhibitors (SSRIs) and venlafaxine in a large and naturalistic patient material, in order to provide tentative dose recommendations for pregnant women.

Methods

Using patient data from two routine therapeutic drug monitoring (TDM) services in Norway with linkage to the national birth registry, dose-adjusted serum drug concentrations of SSRIs and venlafaxine during pregnancy were compared to the women’s own baseline (non-pregnant) values, using a linear mixed model.

Findings

Overall, the TDM databases contained 196,726 serum concentration measurements from 54,393 women. After data linkage and drug selection (SSRIs or venlafaxine only), we identified 367 analyses obtained from a total of 290 pregnancies in 281 women, and 420 baseline observations from the same women. Serum concentrations in the third trimester were significantly lower than baseline for paroxetine (–51%; 95% confidence interval [CI], –66%, –30%; p<0.001), fluvoxamine (–56%; CI, –75%, –23%; p = 0.004) and citalopram (–24%; CI, –38%, –7%; p = 0,007), and higher than baseline for sertraline (+68%; CI, +37%, +106%; p<0.001). For escitalopram, fluoxetine and venlafaxine concentrations did not change significantly.

Conclusions

For paroxetine and fluvoxamine the pronounced decline in maternal drug serum concentrations in pregnancy may necessitate a dose increase of about 100% during the third trimester in order to maintain stable concentrations. For fluoxetine, venlafaxine, citalopram, escitalopram and sertraline, the present study indicates that dose adjustments are generally not necessary during pregnancy.

Transcriptional Regulation of CYP2D6 Expression

CYP2D6-mediated drug metabolism exhibits large interindividual variability. Although genetic variations in the CYP2D6 gene are well known contributors to the variability, the sources of CYP2D6 variability in individuals of the same genotype remain unexplained. Accumulating data indicate that transcriptional regulation of CYP2D6 may account for part of CYP2D6 variability. Yet, our understanding of factors governing transcriptional regulation of CYP2D6 is limited. Recently, mechanistic studies of increased CYP2D6-mediated drug metabolism in pregnancy revealed two transcription factors, small heterodimer partner (SHP) and Krüppel-like factor 9, as a transcriptional repressor and an activator, respectively, of CYP2D6. Chemicals that increase SHP expression (e.g., retinoids and activators of farnesoid X receptor) were shown to downregulate CYP2D6 expression in the humanized mice as well as in human hepatocytes. This review summarizes the series of studies on the transcriptional regulation of CYP2D6 expression, potentially providing a basis to better understand the large interindividual variability in CYP2D6-mediated drug metabolism.

The Risk of Congenital Heart Anomalies Following Prenatal Exposure to Serotonin Reuptake Inhibitors-Is Pharmacogenetics the Key?

Serotonin reuptake inhibitors (SRIs) are often prescribed during pregnancy. Previous studies that found an increased risk of congenital anomalies, particularly congenital heart anomalies (CHA), with SRI use during pregnancy have created concern among pregnant women and healthcare professionals about the safety of these drugs. However, subsequent studies have reported conflicting results on the association between CHA and SRI use during pregnancy. These discrepancies in the risk estimates can potentially be explained by genetic differences among exposed individuals. In this review, we explore the potential pharmacogenetic predictors involved in the pharmacokinetics and mechanism of action of SRIs, and their relation to the risk of CHA. In general, the risk is dependent on the maternal concentration of SRIs and the foetal serotonin level/effect, which can be modulated by the alteration in the expression and/or function of the metabolic enzymes, transporter proteins and serotonin receptors involved in the serotonin signalling of the foetal heart development. Pharmacogenetics might be the key to understanding why some children exposed to SRIs develop a congenital heart anomaly and others do not.

CYP2D6 Is Inducible by Endogenous and Exogenous Corticosteroids

Although cytochrome P450 (CYP) 2D6 has been widely considered to be noninducible on the basis of human hepatocyte studies, in vivo data suggests that it is inducible by endo- and xenobiotics. Therefore, we investigated if the experimental conditions routinely used in human hepatocyte studies may be a confounding factor in the lack of in vitro induction of CYP2D6. Sandwich cultured human hepatocytes (SCHH) were preincubated with or without dexamethasone (100 nM) for 72 hours before incubation with 1μM endogenous (cortisol or corticosterone) or exogenous (dexamethasone or prednisolone) corticosteroids. At 72 hours, CYP2D6 mRNA, protein, and activity were quantified by real-time quantitative polymerase chain reaction, quantitative proteomics, and formation of dextrorphan from dextromethorphan, respectively. In the absence of supplemental dexamethasone, CYP2D6 activity, mRNA, and protein were significantly and robustly (>10-fold) induced by all four corticosteroids. However, this CYP2D6 induction was abolished in cells preincubated with supplemental dexamethasone. These data show, for the first time, that CYP2D6 is inducible in vitro but the routine presence of 100 nM dexamethasone in the culture medium masks this induction. Our cortisol data are in agreement with the clinical observation that CYP2D6 is inducible during the third trimester of pregnancy when the plasma concentrations of cortisol increase to ∼1μM. These findings, if confirmed in vivo, have implications for predicting CYP2D6-mediated drug-drug interactions and call for re-evaluation of regulatory guidelines on screening for CYP2D6 induction by xenobiotics. Our findings also suggest that cortisol may be a causative factor in the in vivo induction of CYP2D6 during pregnancy.

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.

Is third trimester serotonin reuptake inhibitor use associated with postpartum hemorrhage?

As serotonin reuptake inhibitor (SRI) use may decrease platelet function, previous research has shown a relationship between SRI use and an increased risk for bruising and bleeding. The literature regarding the association between SRI use during pregnancy and increased bleeding at delivery, referred to as postpartum hemorrhage (PPH), is mixed. In secondary analyses from two prospective observational studies of pregnant women with mood disorders, 263 women were exposed to an SRI (n = 51) or not (n = 212) in the third trimester. To be precise, we used the terminology estimated blood loss (EBL) >600 cc rather than the term PPH because the current definition of PPH differs. The occurrence of EBL >600 cc was determined using the Peripartum Events Scale (PES) completed from obstetrical records by a blinded medically trained member of the study team. EBL >600 cc occurred in 8.7% of women in this cohort. There was no statistically significant difference in the rates of EBL >600 cc in the 24 h after delivery in women taking SRIs during the third trimester (9.8%) compared to non-exposed women (8.5%). Utilizing generalizing estimating equations, the odds of EBL >600 cc in each group were not significantly different (OR 1.17, CI-0.41-3.32, p = 0.77). When the SRI group was limited to women with exposure at the time of delivery, the difference in the odds of EBL >600 cc was unchanged (OR 1.16, CI = 0.37-3.64, p = 0.79). In population, both third trimester and use at delivery of SRIs during pregnancy was not associated with an increased risk of excessive blood loss.

Early pregnancy exposure to selective serotonin reuptake inhibitors, risks of major structural malformations, and hypothesized teratogenic mechanisms

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) are commonly used to manage antenatal depression. Hence, the aim of this systematic review is to assess the prevalence of birth defects associated with pregnancy exposure to such agents and summarize the hypothesized teratogenic mechanisms.

AREAS COVERED

Medical literature published in English (1980 - June 2015) was electronically searched to identify all articles reporting an increased prevalence of birth defects associated with prenatal SSRI exposure and hypothesizing teratogenic mechanisms.

EXPERT OPINION

The only recurrent pattern of congenital anomalies associated with antenatal SSRI exposure is heart defects. SSRIs may alter the function of serotonin and related receptors which are involved in the development of the monoamine-dependent cardiac structures. Nevertheless, the magnitude of this increase and, thus, its clinical significance are unclear. Therefore, a cautious approach of using SSRI during pregnancy only in the case of major depressive episodes should be applied. However, this risk should be balanced against the risks associated with the worsening of depressive symptoms, and take into consideration the large number of studies that found no associations between transplacental SSRI exposure and cardiac anomalies. Prenatal ultrasonography and Doppler sonography to detect early cardiac defects are also advisable. Non-pharmacological approaches are preferred for less severe psychiatric disorders.

Association of 2 neurotrophic factor polymorphisms with efficacy of paroxetine in patients with major depressive disorder in a Chinese population

BACKGROUND

To evaluate the influence of the single nucleotide polymorphism (SNP) rs 6265 in the brain-derived neurotrophic factor (BDNF) gene and 21 SNPs of the glial cell line-derived neurotrophic factor (GDNF) gene on the efficacy of paroxetine in patients with major depressive disorder (MDD).

METHODS

Genotyping for BDNF and GDNF polymorphisms was performed in 298 patients with MDD who started 20 mg paroxetine per day and had their plasma concentrations measured after 6 weeks. The SNPs were selected from the HapMap Chinese ethnic group and literature reports. Changes in the severity of MDD were assessed with the Hamilton Depression Rating Scale (HAM-D) at baseline and at a 6-week follow-up. Paroxetine plasma concentration was measured using high-performance liquid chromatography with fluorescence detection. The Sequenom MassArray system was used for genotyping.

RESULTS

At the 6-week follow-up, 219 of the 298 patients (73.5%) were responders and 79 patients (26.5%) were nonresponders to paroxetine treatment. The lower threshold concentration of paroxetine for response was 50 ng/mL, and a linear relationship was found between paroxetine plasma concentration and clinical response. The allele types for the SNPs rs 6265 (P < 0.001), rs 2973049 (P = 0.005), and rs 2216711 (P = 0.006) demonstrated significant associations with paroxetine treatment remission at week 6.

CONCLUSIONS

Genetic variants in the BDNF and GDNF regions may be indicators of treatment response to paroxetine in patients with MDD.