High Plasma Concentrations of Zidovudine (AZT) Do Not Parallel Intracellular Concentrations of AZT-Triphosphates in Infants During Prevention of Mother-to-Child HIV-1 Transmission

Influence of maternal use of tenofovir disoproxil fumarate or zidovudine in Vietnamese pregnant women with HIV on infant growth, renal function, and bone health

Tenofovir disoproxil fumarate (TDF) is still widely prescribed for human immunodeficiency virus (HIV)-infected pregnant women, despite its renal and bone toxicity. Although TDF-exposed infants often show transient growth impairment, it is not clear whether maternal TDF causes infantile rickets via maternal/fetal renal dysfunction in Asian populations. This prospective observational study was conducted in Vietnam and involved pregnant HIV-infected women treated with TDF-based regimen (TDF group) or zidovudine-based regimen (AZT-group). At birth, 3, 12, and 18 months of age, and included body length, weight, head circumference, serum alkaline phosphatase (ALP), creatinine, calcium, phosphorus, urine-β2-microglobulin (U-BMG), percentage of tubular reabsorption of phosphate (%TRP), and radiographic wrist score for rickets. Age-adjusted multivariate linear regression analysis evaluated the association of TDF/AZT use during pregnancy with fetal renal function and bone health. The study included 63 mother-infant pairs (TDF group = 53, AZT group = 10). In the mothers, detectable U-BMG (>252 μg/L) was observed more frequently in the TDF- than AZT group (89 vs 50%, p<0.001), but other renal/bone parameters were similar. In infants, maternal TDF use was not associated with growth impairment, renal dysfunction, or abnormal bone findings, but with a slightly higher ALP levels (p = 0.019). However, shorter length was associated with maternal AZT (p = 0.021), and worse radiographic scores were associated with LPV/r (p = 0.024). In Vietnamese population, TDF usage during pregnancy was not associated with infant transient rickets, growth impairment, or renal dysfunction, despite mild maternal tubular impairment. Maternal AZT and LPV/r influenced infant growth and bone health, though further studies are needed to confirm this finding.

Optimizing Pediatric Dosing Recommendations and Treatment Management of Antiretroviral Drugs Using Therapeutic Drug Monitoring Data in Children Living With HIV

INTRODUCTION

This review summarizes the current dosing recommendations for antiretroviral (ARV) drugs in the international pediatric guidelines of the World Health Organization (WHO), US Department of Health and Human Services (DHHS), and Pediatric European Network for Treatment of AIDS (PENTA), and evaluates the research that informed these approaches. We further explore the role of data generated through therapeutic drug monitoring in optimizing the dosing of ARVs in children.

METHODS

A PubMed search was conducted for the literature on ARV dosing published in English. In addition, the registration documentation of European Medicines Agency and the US Food and Drug Administration for currently used ARVs and studies referenced by the WHO, DHHS, and EMA guidelines were screened. Resulting publications were screened for papers containing data on the area under the concentration-time curve, trough concentration, and peak concentration. Studies with enrolled participants with a median or mean age of ≥18 years were excluded. No restriction on publishing date was applied.

DISCUSSION AND CONCLUSION

Pediatric ARV dosing is frequently based on data obtained from small studies and is often simplified to facilitate dosing in the context of a public health approach. Pharmacokinetic parameters of pediatric ARVs are subject to high interpatient variation and this leads to a potential risk of underdosing or overdosing when drugs are used in real life. To ensure optimal use of ARVs and validate dosing recommendations for children, it is essential to monitor ARV dosing more thoroughly with larger sample sizes and to include diverse subpopulations. Therapeutic drug monitoring data generated in children, where available and affordable, have the potential to enhance our understanding of the appropriateness of simplified pediatric dosing strategies recommended using a public health approach and to uncover suboptimal dosing or other unanticipated issues postmarketing, further facilitating the ultimate goal of optimizing pediatric ARV treatment.

Prevention and treatment of HIV infection in neonates: evidence base for existing WHO dosing recommendations and implementation considerations

INTRODUCTION

Antiretroviral drugs are used in neonates for prevention and treatment of HIV infection. Use of antiretrovirals to prevent perinatal HIV transmission is well established. Early identification of neonates infected with HIV and rapid initiation of combination antiretroviral treatment during the neonatal period is now recommended by WHO and DHHS. However, few antiretrovirals are available in formulations suitable for neonates and there are limited safety and pharmacokinetic data for most antiretrovirals in neonates. Areas covered: We summarize existing neonatal antiretroviral safety and pharmacokinetic information and discuss implementation considerations for programs providing antiretrovirals to neonates and young infants. Expert commentary: Antiretrovirals currently recommended by WHO for use in neonates are zidovudine, lamivudine, lopinavir/ritonavir, nevirapine, and raltegravir. Significant implementation challenges exist to the widespread use of these antiretrovirals in neonates. Optimal, feasible treatment of HIV-exposed and HIV-infected newborns will require development of practical neonatal dosage forms and their study in neonates for a wide range of antiretrovirals.