Antiretroviral pharmacology: special issues regarding pregnant women and neonates

The importance of assessing and addressing mental health barriers to PrEP use during pregnancy and postpartum in sub-Saharan Africa: state of the science and research priorities

Introduction

Pregnant and postpartum women (PPW) in sub‐Saharan Africa are at disproportionately high risk of HIV infection compared to non‐pregnant women. When used consistently, pre‐exposure prophylaxis (PrEP) can prevent HIV acquisition and transmission to the foetus or infant during these critical periods. Recent studies have demonstrated associations between mental health challenges (e.g. depression and traumatic stress associated with intimate partner violence) and decreased PrEP adherence and persistence, particularly among adolescents, younger women and women in the postpartum period. However, mental health is not currently a major focus of PrEP implementation research and programme planning for PPW.

Discussion

PrEP implementation programmes for PPW need to assess and address mental health barriers to consistent PrEP use to ensure effectiveness and sustainability in routine care. We highlight three key research priorities that will support PrEP adherence and persistence: (1) include mental health screening tools in PrEP implementation research with PPW, both to assess the feasibility of integrating these tools into routine antenatal and postpartum care and to ensure that limited resources are directed towards women whose symptoms may interfere most with PrEP use; (2) identify cross‐cutting, transdiagnostic psychological mechanisms that affect consistent PrEP use during these periods and can realistically be targeted with intervention in resource‐limited settings; and (3) develop/adapt and test interventions that target those underlying mechanisms, leveraging strategies from existing interventions that have successfully mitigated mental health barriers to antiretroviral therapy use among people with HIV.

Conclusions

For PPW, implementation of PrEP should be guided by a robust understanding of the unique psychological difficulties that may act as barriers to uptake, adherence and persistence (i.e. sustained adherence over time). We strongly encourage PrEP implementation research in PPW to incorporate validated mental health screening tools and ultimately treatment in routine antenatal and postnatal care, and we stress the potential public health benefits of identifying women who face mental health barriers to PrEP use.

Ethical issues in therapeutic use and research in pregnant and breastfeeding women

Pregnant or potentially pregnant women have historically been excluded from clinical trials of new medications. However, it is increasingly recognised that it is imperative to generate evidence from the population in whom the drugs are likely to be used to inform safe, evidence-based shared clinical decision making. Reluctance by researchers and regulators to perform such studies often relates to concerns about risk, particularly to the foetus. However, this must be offset against the risk of untreated disease or using a drug in pregnancy where safety, efficacy and dosing information are not known. This review summarises the historical perspective, and the ethical and legal frameworks that inform the conduct of such research, then highlights examples of innovative practice that have enabled high quality, ethical research to proceed to inform the evidence-based use of medication in pregnancy.

Atovaquone-proguanil exposure in pregnancy and risk for adverse fetal and infant outcomes: A retrospective analysis

BACKGROUND

Malaria in pregnancy can cause severe maternal and fetal complications. Chloroquine (CQ) and mefloquine (MQ) are recommended for chemoprophylaxis in pregnancy, but are not always suitable. Atovaquone-proguanil (AP) might be a viable option for malaria prevention in pregnancy, but more safety data are needed.

METHODS

Data for pregnancies and live births among active duty military women, 2003-2014, from the Department of Defense Birth and Infant Health Research program were linked with pharmacy data to determine antimalarial exposure. Multivariable Cox and logistic regression models were used to assess the relationship of antimalarial exposure with fetal and infant outcomes, respectively.

RESULTS

Among 198,164 pregnancies, 50 were exposed to AP, 156 to MQ, and 131 to CQ. Overall, 17.6% of unexposed pregnancies and 28.0%, 16.0%, and 6.1% of pregnancies exposed to AP, MQ, and CQ, respectively, ended in fetal loss (spontaneous abortion or stillbirth) (adjusted hazard ratios [aHR] = 1.46, 95% confidence interval [CI] 0.87-2.46; aHR = 1.06, 95% CI 0.72-1.57; and aHR = 0.47, 95% CI 0.24-0.94, respectively).

CONCLUSIONS

The small number of AP exposed pregnancies highlights the difficulty in assessing safety. While definitive conclusions are not possible, these data suggest further research of AP exposure in pregnancy and fetal loss is warranted.

TWITTER LINE

More research on fetal loss following atovaquone-proguanil exposure in pregnancy is warranted.

Modelling the potential impact of providing preexposure prophylaxis in pregnant and breastfeeding women in South Africa

OBJECTIVE

HIV-uninfected pregnant and breastfeeding women are at high risk of HIV acquisition, contributing to vertical transmission of HIV. Preexposure prophylaxis (PrEP) is safe in pregnancy, but PrEP in pregnancy is not policy in many countries including South Africa. We evaluated the potential impact of providing PrEP for pregnant/breastfeeding women using a HIV model for South Africa.

METHODS

Our model considers two scenarios: a conservative scenario that matches the experience reported in the Kenyan PrEP programme for pregnant women (probability of uptake = 32% and 11% in high-risk and low-risk women, respectively); and an optimistic scenario with PrEP initiated by 80% of all pregnant women. We compared this with PrEP for female sex workers, MSM and adolescent girls/young women. Women are assumed to remain on PrEP throughout pregnancy and breastfeeding, and an equivalent average PrEP duration (2 years) is assumed in other scenarios.

RESULTS

Between 2020 and 2030, if PrEP is provided to pregnant/breastfeeding mothers, we project a 2.5% reduction in total HIV transmission [95% credibility interval (CI): 2.4-2.6%] in the conservative scenario and 7.2% (95% CI: 6.8-7.5%) in the optimistic scenario, which is similar to that in the female sex worker and MSM PrEP scenarios (1.9% and 3.0%, respectively). Without PrEP, 76 000 (95% CI: 64 000-90 000) new cases of vertical transmission are expected; PrEP provision may reduce these infections by 13% (95% CI: 13-14%) in the conservative scenario and 41% (95% CI: 39-44%) in the optimistic scenario.

CONCLUSION

High levels of uptake of and adherence to PrEP among pregnant/breastfeeding women could substantially reduce maternal and infant HIV acquisition in South Africa.

In Vitro Study on the Effect of Maraviroc or Dolutegravir on Bilirubin to Albumin Binding

We performed an in vitro evaluation of the effect of maraviroc or dolutegravir on bilirubin to albumin binding. At typical treatment and low albumin concentrations, maraviroc had no impact, while dolutegravir affected bilirubin to albumin binding to an equivalent extent as sulfisoxazole. However in vivo, neither is likely to significantly impact bilirubin to albumin binding because of their low concentrations relative to albumin.

Drug Dosing in Pregnant Women: Challenges and Opportunities in Using Physiologically Based Pharmacokinetic Modeling and Simulations

The unmet medical need of providing evidence‐based pharmacotherapy for pregnant women is recognized by the regulatory bodies. Physiologically based pharmacokinetic (PBPK) modeling offers an attractive platform to quantify anticipated changes in the pharmacokinetics (PKs) of drugs during pregnancy. Recent publications applying a pregnancy PBPK module to the prediction of maternal and fetal exposure of drugs are summarized. Future opportunities to use PBPK models to predict breast milk exposure and assess human fetotoxicity risks are presented.

Patterns of efavirenz use as first-line antiretroviral therapy in the United States: 1999-2015

BACKGROUND

Efavirenz has been a mainstay of antiretroviral therapy (ART) for over 15 years in the US. Its association with neuropsychiatric side effects may influence clinical prescribing and management.

METHODS

We included HIV-infected adults enrolled in care at seven sites across the US, who initiated combination ART between 1999 and 2015. We examined the proportion initiating and continuing on efavirenz, overall and by mental health status. Log binomial and Cox models were used to estimate associations between mental health, clinical and sociodemographic characteristics and initiating or switching from efavirenz as first-line ART.

RESULTS

Of the 8,230 participants included, 3,710 (45%) initiated efavirenz. In multivariable analyses, prior mono- or dual-ART, ART initiation after 2006, being female, intravenous drug use, antidepressant prescription, previous mental health diagnosis and baseline CD4+ T-cell count >350 cells/mm3 were inversely associated with initiating efavirenz. Participants initiating efavirenz had a faster time to a regimen switch, compared with those initiating an efavirenz-free regimen (P-value <0.01). Among efavirenz initiators, starting efavirenz in more recent time periods and a previous mental health diagnosis were associated with faster time to switching from efavirenz. Despite this, 40-50% of participants with a previous mental health diagnosis initiated and continued on efavirenz for much of the follow-up period.

CONCLUSIONS

Multiple clinical factors, including mental health diagnoses, appeared to influence efavirenz use. While mental health diagnosis status and more recent treatment starts were associated with shorter duration of efavirenz therapy, a previous mental health diagnosis did not preclude efavirenz initiation or continuation in many participants.

Delivering preexposure prophylaxis to pregnant and breastfeeding women in Sub-Saharan Africa: the implementation science frontier

HIV acquisition during pregnancy and postpartum periods remains high despite increased access to and initiation of antiretroviral therapy in sub-Saharan Africa. Moreover, maternal seroconversion during pregnancy and breastfeeding remains a source of significant paediatric HIV infection in the region. In order to curb vertical HIV transmission, HIV acquisition during pregnancy and lactation must significantly decline. Biological and behavioural factors contribute to high HIV incidence, including hormonal changes that alter genital mucosal surfaces, and frequent condomless sex with HIV-infected partners or partners of unknown serostatus. Pregnant and breastfeeding women who are at risk of HIV acquisition during pregnancy and lactation require female controlled interventions such as pre-exposure prophylaxis (PrEP) to prevent HIV acquisition during those particularly vulnerable periods. Before PrEP scale up for pregnant and lactating women, there is an urgent need for operations research to evaluate how best to provide PrEP to pregnant and breastfeeding women in settings of high HIV incidence. This should include how to: (1) integrate PrEP delivery and counselling into antenatal and postnatal care, (2) ensure optimal adherence during at-risk periods, and (3) target PrEP for maximum impact, including reaching pregnant and breastfeeding young women. In light of current knowledge on the safety of PrEP in pregnancy and breastfeeding, next steps are needed to ensure barriers to PrEP effectiveness are addressed.

Etravirine Pharmacokinetics in HIV-Infected Pregnant Women

Background: The study goal was to describe etravirine pharmacokinetics during pregnancy and postpartum in HIV-infected women.

Methods: IMPAACT P1026s and PANNA are on-going, non-randomized, open-label, parallel-group, multi-center phase-IV prospective studies in HIV-infected pregnant women. Intensive steady-state 12-h pharmacokinetic profiles were performed from 2nd trimester through postpartum. Etravirine was measured at two labs using validated ultra performance liquid chromatography (detection limits: 0.020 and 0.026 mcg/mL).

Results: Fifteen women took etravirine 200 mg twice-daily. Etravirine AUC_0–12 was higher in the 3rd trimester compared to paired postpartum data by 34% (median 8.3 vs. 5.3 mcg*h/mL, p = 0.068). Etravirine apparent oral clearance was significantly lower in the 3rd trimester of pregnancy compared to paired postpartum data by 52% (median 24 vs. 38 L/h, p = 0.025). The median ratio of cord blood to maternal plasma concentration at delivery was 0.52 (range: 0.19–4.25) and no perinatal transmission occurred.

Conclusion: Etravirine apparent oral clearance is reduced and exposure increased during the third trimester of pregnancy. Based on prior dose-ranging and safety data, no dose adjustment is necessary for maternal health but the effects of etravirine in utero are unknown. Maternal health and infant outcomes should be closely monitored until further infant safety data are available.

Clinical Trial registration: The IMPAACT protocol P1026s and PANNA study are registered at ClinicalTrials.gov under NCT00042289 and NCT00825929.

Meconium aspiration syndrome in infants of HIV-positive women: a case-control study

OBJECTIVE

Our aim was to determine whether maternal HIV infection in the current era is associated with an increased incidence of meconium aspiration syndrome (MAS) in their infants.

METHODS

Infants born to 149 HIV-positive women at our hospital over a 5-year period were compared with infants born to HIV-negative women in a retrospective case-control study. Charts of all 298 patients included in the study were reviewed for maternal and infant demographics, HIV treatment, vertical transmission and untoward events at delivery or during the hospital course.

RESULTS

When compared with HIV-negative women, a greater proportion of HIV-positive women had meconium-stained amniotic fluid (MSAF), 33% vs. 13%, P<0.001; and thick MSAF, 17% vs. 5%, P<0.001, respectively. Seven of 298 infants were admitted to the neonatal intensive care unit for MAS; all seven were born to HIV-positive women (P=0.015). Although in utero exposure to illicit drugs is a reported risk factor for meconium staining of the amniotic fluid and such drug exposure was more common among our HIV-positive sample, controlling for this and other possible covariates did not greatly reduce the association of HIV status with meconium-related complications of delivery.

CONCLUSIONS

Infants born to HIV-positive women had significantly more MSAF and MAS than infants born to non-infected women. It is unclear whether this association results from maternal HIV infection itself or from anti-retroviral therapy. Maternal and infant care providers should be prepared for this complication when attending to the deliveries of HIV-positive women.

Pharmacologic prevention of human immunodeficiency virus in women: practical approaches for the obstetrician and gynecologist

IMPORTANCE

Obstetricians and gynecologists (Ob-Gyns) play a crucial role in efforts to detect and prevent human immunodeficiency virus (HIV) infection in women. Multiple strategies can be implemented into general practice as part of a comprehensive primary women's health care agenda. Educational and behavioral strategies to reduce HIV acquisition in women can now be supplemented with pharmacologic measures.

OBJECTIVE

This article aimed to review the literature regarding preexposure prophylaxis (PrEP) for HIV prevention in women. After reading this article, readers should be able to describe available methods to prevent HIV acquisition in women, select appropriate candidates for PrEP, and outline the steps necessary for initiation of PrEP.

EVIDENCE ACQUISITION

A review of the available literature was obtained by a PubMed search of HIV prevention, women, preexposure prophylaxis, and PrEP. Additional information was obtained from the Centers for Disease Control and Prevention; the American Congress of Obstetricians and Gynecologists; and expert opinion in the fields of obstetrics and gynecology, infectious diseases, and reproductive infectious diseases.

RESULTS

This review of the literature summarizes the efficacy of PrEP in HIV prevention and identifies limitations and barriers of PrEP. Women who are at risk for HIV acquisition and candidates for PrEP are clearly defined. Certain populations face unique challenges in HIV prevention and the administration of PrEP, and clinical guidelines and references are provided. This article provides a practical guide for the initiation, maintenance, and discontinuation of PrEP for the general Ob-Gyn.

CONCLUSIONS

Preexposure prophylaxis is an effective measure to prevent HIV in women. The Ob-Gyn plays a key role in the identification of at-risk women and the initiation of HIV prevention.

RELEVANCE

This information is relevant to general Ob-Gyns and other women's health providers.

Pharmacokinetics of Once Versus Twice Daily Darunavir in Pregnant HIV-Infected Women

OBJECTIVE

To describe darunavir (DRV) pharmacokinetics with once-and twice-daily dosing during pregnancy and postpartum in HIV-infected women.

DESIGN

Women were enrolled in International Maternal Pediatric Adolescent AIDS Clinical Trials Network Protocol P1026s, a prospective nonblinded study of antiretroviral pharmacokinetics in HIV-infected pregnant women that included separate cohorts receiving DRV/ritonavir dosed at either 800 mg/100 mg once daily or 600 mg/100 mg twice daily.

METHODS

Intensive steady-state 12- or 24-hour pharmacokinetic profiles were performed during the second trimester, third trimester, and postpartum. DRV was measured using high-performance liquid chromatography (detection limit: 0.09 μg/mL).

RESULTS

Pharmacokinetic data were available for 64 women (30 once daily and 34 twice daily dosing). Median DRV area under the concentration-time curve (AUC) and maximum concentration were significantly reduced during pregnancy with both dosing regimens compared with postpartum, whereas the last measurable concentration (Clast) was also reduced during pregnancy with once daily DRV. DRV AUC with once daily dosing was reduced by 38% during the second trimester and by 39% during the third trimester. With twice daily dosing, DRV AUC was reduced by 26% in both trimesters. The median (range) ratio of cord blood/maternal delivery DRV concentration in 32 paired samples was 0.18 (range: 0-0.82).

CONCLUSIONS

DRV exposure is reduced by pregnancy. To achieve DRV plasma concentrations during pregnancy equivalent to those seen in nonpregnant adults, an increased twice daily dose may be necessary. This may be especially important for treatment-experienced women who may have developed antiretroviral resistance mutations.

Pharmacometrics in pregnancy: An unmet need

Pregnant women and their fetuses are orphan populations with respect to the safety and efficacy of drugs. Physiological and absorption, distribution, metabolism, and excretion (ADME) changes during pregnancy can significantly affect drug pharmacokinetics (PK) and may necessitate dose adjustment. Here, the specific aspects related to the design, execution, and analysis of clinical studies in pregnant women are discussed, underlining the unmet need for top-down pharmacometrics analyses and bottom-up modeling approaches. The modeling tools that support data analysis for the pregnancy population are reviewed, with a focus on physiologically based pharmacokinetics (PBPK) and population pharmacokinetics (POP-PK). By integrating physiological data, preclinical data, and clinical data (e.g., via POP-PK) to quantify anticipated changes in the PK of drugs during pregnancy, the PBPK approach allows extrapolation beyond the previously studied model drugs to other drugs with well-characterized ADME characteristics. Such a systems pharmacology approach can identify drugs whose PK may be altered during pregnancy, guide rational PK study design, and support dose adjustment for pregnant women.

Raltegravir in vitro effect on bilirubin binding

Drugs that displace bilirubin from albumin may increase the risk of kernicterus in neonates. We evaluated the effect of raltegravir on bilirubin-albumin binding in pooled neonatal serum using the peroxidase method. Raltegravir had minimal effect on bilirubin-albumin binding at concentrations of 5 and 10 µM, caused a small but statistically significant increase in unbound bilirubin at 100 µM and caused potentially harmful increases at 500 and 1000 µM. Our data suggest that the effect of raltegravir on neonatal bilirubin binding is unlikely to be clinically significant at typical peak concentrations reached with usual dosing.

Antiretroviral therapy, pregnancy, and birth defects: a discussion on the updated data

An increasing number of HIV-infected women of childbearing age are initiating antiretroviral therapy (ART) worldwide. This review aims to discuss updated data of the eligible ART regimens and their role in inducing birth defects in utero. Zidovudine and lamivudine plus a non-nucleoside reverse-transcriptase inhibitor or protease inhibitor (PI) is the first-line regimen applied. The role of zidovudine exposition monotherapy or associated with other ART in inducing birth defects remains inconclusive. The main organ systems involved are genitourinary and cardiovascular. For HIV-infected pregnant women, World Health Organization (WHO) guidelines up to 2010 recommend the same group of drugs that are prescribed to nonpregnant women. The exception is efavirenz, which has been associated with an increase in the risk of teratogenicity. Increased rates of birth defects were found in large cohorts and computational studies conducted recently in infants exposed to efavirenz-containing regimens. The combination of zidovudine and lamivudine and lopinavir/ritonavir is one of the most used ART regimens for prevention of mother-to-child-transmission. Conflicting data about the role of PI exposure in utero and birth defects have been reported. However, a reduced number of studies evaluating the role of PI in inducing birth defects in women are available. An association between prematurity and PI exposure in pregnancy was extensively described. Some questions arise due to the tendency of initiating ART early in the life of HIV-infected individuals or those at risk of infection. Longtime exposure to different ART regimens and the potential effect of birth-defect induction in pregnancy are not completely understood. Developing regions harbor the highest numbers of women of reproductive age exposed to ART. Most of the largest and expressive data come from developed countries, and could not be sufficiently representative of pregnant women living in developing countries.

Therapeutic drug monitoring in pregnancy

Therapeutic drug monitoring (TDM) is commonly recommended to optimize drug dosing regimens of various medications. It has been proposed to guide therapy in pregnant women, in whom physiological changes may lead to altered pharmacokinetics resulting in difficulty in predicting the appropriate drug dosage. Ideally, TDM may play a role in enhancing the effectiveness of treatment while minimizing toxicity of both the mother and fetus. Monitoring of drug levels may also be helpful in assessing adherence to prescribed therapy in selected cases. Limitations exist as therapeutic ranges have only been defined for a limited number of drugs and are based on data obtained in nonpregnant patients. TDM has been suggested for anticonvulsants, antidepressants, and antiretroviral drugs, based on pharmacokinetic studies that have shown reduced drug concentrations. However, there is only relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Further studies are required to determine whether implementation of TDM during pregnancy improves outcome and is associated with any benefit beyond that achieved by clinical judgment alone. The cost effectiveness of TDM programs during pregnancy also remains to be examined.

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.

Gynecologic and other infections in pregnancy

The treatment of gynecologic and other infections in obstetric patients involves consideration of the physiologic changes of pregnancy, the clinical implications of the infection for the patient as well as the fetus, and the safety of antimicrobials available for therapy. This article highlights the treatment of infections of the vagina, uterus, and urinary tract, with a focus on how therapy changes in obstetric patients. In addition, the emergency department management of other clinically important infections in pregnancy, such as those caused by the human immunodeficiency virus, influenza viruses, methicillin-resistant Staphylococcus aureus, Parvovirus, Listeria, and others is reviewed.

World Health Organization generic protocol to assess drug-resistant HIV among children <18 months of age and newly diagnosed with HIV in resource-limited countries

Increased use of nonnucleoside reverse transcriptase inhibitors (NNRTIs) in pregnant and breastfeeding women will result in fewer children infected with human immunodeficiency virus (HIV). However, among children infected despite prevention of mother-to-child transmission (PMTCT), a substantial proportion will acquire NNRTI-resistant HIV, potentially compromising response to NNRTI-based antiretroviral therapy (ART). In countries scaling up PMTCT and pediatric ART programs, it is crucial to assess the proportion of young children with drug-resistant HIV to improve health outcomes and support national and global decision making on optimal selection of pediatric first-line ART. This article summarizes a new World Health Organization surveillance protocol to assess resistance using remnant dried blood spot specimens from a representative sample of children aged <18 months being tested for early infant diagnosis.

Effect of pregnancy on emtricitabine pharmacokinetics

OBJECTIVES

The aim of the study was to describe emtricitabine pharmacokinetics during pregnancy and postpartum.

METHODS

The International Maternal Pediatric and Adolescent AIDS Clinical Trials (IMPAACT), formerly Pediatric AIDS Clinical Trials Group (PACTG), study P1026s is a prospective pharmacokinetic study of HIV-infected pregnant women taking antiretrovirals for clinical indications, including a cohort taking emtricitabine 200 mg once daily. Intensive steady-state 24-hour emtricitabine pharmacokinetic profiles were performed during the third trimester and 6-12 weeks postpartum, and on maternal and umbilical cord blood samples collected at delivery. Emtricitabine was measured by liquid chromatography-mass spectrometry with a quantification limit of 0.0118 mg/L. The target emtricitabine area under the concentration versus time curve, from time 0 to 24 hours post dose (AUC(0-24) ), was ≥7 mg h/L (≤30% reduction from the typical AUC of 10 mg h/L in nonpregnant historical controls). Third-trimester and postpartum pharmacokinetics were compared within subjects.

RESULTS

Twenty-six women had pharmacokinetics assessed during the third trimester (median 35 weeks of gestation) and 22 postpartum (median 8 weeks postpartum). Mean [90% confidence interval (CI)] emtricitabine pharmacokinetic parameters during the third trimester vs. postpartum were, respectively: AUC: 8.0 (7.1-8.9) vs. 9.7 (8.6-10.9) mg h/L (P = 0.072); apparent clearance (CL/F): 25.0 (22.6-28.3) vs. 20.6 (18.4-23.2) L/h (P = 0.025); 24 hour post dose concentration (C(24) ): 0.058 (0.037-0.063) vs. 0.085 (0.070-0.010) mg/L (P = 0.006). The mean cord:maternal ratio was 1.2 (90% CI 1.0-1.5). The viral load was <400 HIV-1 RNA copies/mL in 24 of 26 women in the third trimester, in 24 of 26 at delivery, and in 15 of 19 postpartum. Within-subject comparisons demonstrated significantly higher CL/F and significantly lower C(24) during pregnancy; however, the C(24) was well above the inhibitory concentration 50%, or drug concentration that suppresses viral replication by half (IC(50) ) in all subjects.

CONCLUSIONS

While we found higher emtricitabine CL/F and lower C(24) and AUC during pregnancy compared with postpartum, these changes were not sufficiently large to warrant dose adjustment during pregnancy. Umbilical cord blood concentrations were similar to maternal concentrations.