Oral zidovudine during labor to prevent perinatal HIV transmission, Bangkok: tolerance and zidovudine concentration in cord blood. Bangkok Collaborative Perinatal HIV Transmission Study Group

Antiretroviral Options and Treatment Decisions During Pregnancy

The majority of pediatric human immunodeficiency virus (HIV) infections are the result of vertical transmissions that occur during pregnancy, childbirth, and breastfeeding. The treatment of all pregnant persons living with HIV remains a global health initiative. Early and consistent use of antiretroviral therapy throughout pregnancy and childbirth drastically reduces the risk of perinatal transmission of HIV, resulting in fewer children living with the disease worldwide. Given that the maternal HIV viral load is the strongest predictor of perinatal transmission, suppressive antiretroviral treatment during pregnancy is the principal means to eliminate transmission of HIV from mother to child. With the use of combined antiretroviral therapy, typically with dual-nucleoside reverse transcriptase inhibitors plus an integrase strand transfer inhibitor or a ritonavir-boosted protease inhibitor, HIV-infected mothers can now achieve virologic suppression to undetectable levels and yield a perinatal transmission rate of less than 2%. Important considerations of HIV treatment in pregnancy include the safety and efficacy of antiretroviral drugs, altered pregnancy-related pharmacokinetics, potential for birth defects or adverse neonatal outcomes, and individualized delivery planning based on maternal viral load. This practical review article summarizes the options, considerations, and recommendations for antiretroviral treatment in pregnancy to reduce perinatal HIV transmission and optimize health outcomes for mothers and infants worldwide.

Protecting the fetus against HIV infection: a systematic review of placental transfer of antiretrovirals

BACKGROUND

Maternal-to-fetal transfer of antiretroviral drugs contributes to prevention of vertical transmission of HIV.

OBJECTIVE

This systematic review discusses published studies containing data pertaining to the pharmacokinetics of placental transfer of antiretrovirals in humans, including paired cord and maternal plasma samples collected at the time of delivery as well as ex vivo placental perfusion models.

METHODS

Articles pertaining to placental transfer of antiretrovirals were identified from PubMed, from references of included articles, and from US Department of Health and Human Services Panel on Treatment of HIV-infected Pregnant Women and Prevention of Perinatal Transmission guidelines. Articles from non-human animal models or that had no original maternal-to-fetal transfer data were excluded. PRISMA guidelines were followed.

RESULTS

A total of 103 published studies were identified. Data across studies appeared relatively consistent for the nucleoside reverse transcriptase inhibitors (NRTIs) and the non-nucleotide reverse transcriptase inhibitors (NNRTIs), with cord to maternal ratios approaching 1 for many of these agents. The protease inhibitors atazanavir and lopinavir exhibited consistent maternal-to-fetal transfer across studies, although the transfer may be influenced by variations in drug-binding proteins. The protease inhibitors indinavir, nelfinavir, and saquinavir exhibited unreliable placental transport, with cord blood concentrations that were frequently undetectable. Limited data, primarily from case reports, indicate that darunavir and raltegravir provide detectable placental transfer.

CONCLUSION

These findings appear consistent with current guidelines of using two NRTIs plus an NNRTI, atazanavir/ritonavir, or lopinavir/ritonavir to maximize placental transfer as well as to optimally suppress maternal viral load. Darunavir/ritonavir and raltegravir may reasonably serve as second-line agents.

Coverage of the prevention of mother-to-child transmission program in the Western Cape, South Africa using cord blood surveillance

BACKGROUND

The effectiveness of prevention of mother-to-child transmission of HIV (PMTCT) programs depends on the successful coverage of a series of interventions through pregnancy, intrapartum, and postpartum. Routine monitoring systems based on service data and limited to women on the PMTCT program may overestimate intervention coverage at multiple points along this cascade.

METHODS

Cord blood specimens with individually linked anonymous demographic and pregnancy data were collected from 3 delivery services in the Western Cape Province, South Africa, and screened for HIV. Seropositive specimens were tested for the presence of antiretrovirals. Comparisons were drawn between documented service data and cord blood findings for HIV seroprevalence and antenatal antiretroviral coverage.

RESULTS

A total of 3034 specimens were tested for HIV, 507 (16.7%) of which were HIV seropositive. Of these, 470 (92.7%) were tested for the presence of antiretrovirals, of whom 58.1% had evidence of a standard of care maternal antiretroviral regimen and 73.6% some form of antenatal antiretroviral prophylaxis. Cord blood antiretroviral coverage was lower than that reported by service data. Incomplete antenatal HIV testing accounted for an estimated 46.2% of missed opportunities for transmission reduction.

DISCUSSION

Even in this well-resourced setting, HIV screening and ensuring antenatal compliance with prescribed regimens were the most immediate priorities for reducing vertical transmission. Cord blood surveillance offers a unique opportunity to explore missed opportunities using methods not currently possible from routine antenatal and PMTCT program reporting.

Antiretrovirals for reducing the risk of mother-to-child transmission of HIV infection

BACKGROUND

Antiretroviral drugs reduce viral replication and can reduce mother-to-child transmission of HIV either by lowering plasma viral load in pregnant women or through post-exposure prophylaxis in their newborns. In rich countries, highly active antiretroviral therapy (HAART) which usually comprises three drugs, has reduced the mother-to-child transmission rates to around 1-2%, but HAART is not always available in low- and middle-income countries. In these countries, various simpler and less costly antiretroviral regimens have been offered to pregnant women or to their newborn babies, or to both.

OBJECTIVES

To determine whether, and to what extent, antiretroviral regimens aimed at decreasing the risk of mother-to-child transmission of HIV infection achieve a clinically useful decrease in transmission risk, and what effect these interventions have on maternal and infant mortality and morbidity.

SEARCH STRATEGY

We sought to identify all relevant studies regardless of language or publication status by searching the Cochrane HIV/AIDS Review Group Trials Register, The Cochrane Library, MEDLINE, EMBASE and AIDSearch and relevant conference abstracts. We also contacted research organizations and experts in the field for unpublished and ongoing studies. The original review search strategy was conducted in 2002 and updated in 2006 and again in 2009.

SELECTION CRITERIA

Randomised controlled trials of any antiretroviral regimen aimed at decreasing the risk of mother-to-child transmission of HIV infection compared with placebo or no treatment, or compared with another antiretroviral regimen.

DATA COLLECTION AND ANALYSIS

Two authors independently selected relevant studies, extracted data and assessed trial quality. For the primary outcomes, we used survival analysis to estimate the probability of infants being infected with HIV (the observed proportion) at various specific time-points and calculated efficacy at a specific time as the relative reduction in the proportion infected. Efficacy, at a specific time, is defined as the preventive fraction in the exposed group compared to the reference group, which is the relative reduction in the proportion infected: 1-(Re/Rf). For those studies where efficacy and hence confidence intervals were not calculated, we calculated the approximate confidence intervals for the efficacy using recommended methods. For analysis of results that are not based on survival analyses we present the relative risk for each trial outcome based on the number randomised. No meta-analysis was conducted as no trial assessed identical drug regimens.

MAIN RESULTS

Twenty-five trials including 18,901 participants with a median trial sample size of 627 ranging from 50 to 1,844 participants were included in this update. Twenty-two trials randomised mothers (18 pre-natally and four in labour) and followed up their infants, and three trials randomised infants. The first trial began in April 1991 and assessed zidovudine (ZDV) versus placebo and since then, the type, dosage and duration of drugs to be compared has been modified in each subsequent trial. We present the results stratified by regimen and type of feeding.Antiretrovirals versus placebo In breastfeeding populations, three trials found that:ZDV given to mothers from 36 to 38 weeks gestation, during labour and for 7 days after delivery significantly reduced HIV infection at 4-8 weeks (Efficacy 32.00%; 95% CI 1.50 to 62.50), 3 to 4 months (Efficacy 33.07%; 95% CI 5.57 to 60.57), 6 months (Efficacy 34.55%; 95% CI 9.05 to 60.05), 12 months (Efficacy 34.31%; 95% CI 9.30 to 59.32) and 18 months (Efficacy 29.74%; 95% CI 2.73 to 56.75).ZDV given to mothers from 36 weeks gestation and during labour significantly reduced HIV infection at 4 to 8 weeks (Efficacy 43.78%; 95% CI 8.78 to 78.78) and 3 to 4 months (Efficacy 36.95%; 95% CI 2.94 to 70.96) but not at birth.ZDV plus lamivudine (3TC) given to mothers from 36 weeks gestation, during labour and for 7 days after delivery and to babies for the first 7 days after birth (PETRA 'regimen A') significantly reduced HIV infection (Efficacy 62.75%; 95% CI 40.76 to 84.74) and a combined endpoint of HIV infection or death (Efficacy 62.75 [, ]61.00%; 95% CI 40.76 to 84.74) at 4 to 8 weeks but these effects were not sustained at 18 months.ZDV plus 3TC given to mothers from the start of labour until 7 days after delivery and to babies for the first 7 days after birth (PETRA 'regimen B') significantly reduced HIV infection (Efficacy 41.83%; 95% CI 12.82 to 70.84) and HIV infection or death at 4 to 8 weeks (Efficacy 35.91%; 95% CI 8.41 to 63.41) but the effects were not sustained at 18 months.ZDV plus 3TC given to mothers during labour only (PETRA 'regimen C') with no treatment to babies did not reduce the risk of HIV infection at either 4 to 8 weeks or 18 months.In non-breastfeeding populations, three trials found that:ZDV given to mothers from 14 to 34 weeks gestation and during labour and to babies for the first 6 weeks after birth significantly reduced HIV infection in babies at 18 months (Efficacy 66.22%; 95% CI 33.94 to 98.50).ZDV given to mothers from 36 weeks gestation and during labour with no treatment to babies ('Thai-CDC regimen') significantly reduced HIV infection at 4 to 8 weeks (Efficacy 50.26%; 95% CI 13.80 to 86.72) but not at birthZDV given to mothers from 38 weeks gestation and during labour with no treatment to babies did not influence HIV transmission at 6 months.Longer versus shorter regimens using the same antiretrovirals One trial in a breastfeeding population found that:ZDV given to mothers during labour and to their babies for the first 3 days after birth compared with ZDV given to mothers from 36 weeks and during labour (similar to 'Thai-CDC') resulted in HIV infection rates that were not significantly different at birth, 4-8 weeks, 3 to 4 months, 6 months and 12 months.Three trials in non-breastfeeding populations found that:ZDV given to mothers from 28 weeks gestation during labour and to infants for the first 3 days after birth compared with ZDV given to mothers from 35 weeks gestation through labour and to infants from birth to 6 weeks significantly reduced HIV infection rate at 6 months (Efficacy 45.35 %; 95% CI 1.39 to 89.31) but compared with the same regimen ZDV given to mothers from 28 weeks gestation through labour and to infants from birth to 6 weeks did not result in a statistically significant difference in HIV infection at 6 months. ZDV given to mothers from 35 weeks gestation during labour and to infants for the first 3 days after birth was considered ineffective for reducing transmission rates and this regimen was discontinued.An antenatal/intrapartum course of ZDV used for a median of 76 days compared with an antenatal/intrapartum ZDV regimen used for a median 28 days with no treatment to babies in either group did not result in HIV infection rates that were significantly different at birth and at 3 to 4 months.In a programme where mothers were routinely receiving ZDV in the third trimester of pregnancy and babies were receiving one week of ZDV therapy, a single dose of nevirapine (NVP) given to mothers in labour and to their babies soon after birth compared with a single dose of NVP given to mothers only resulted in HIV infection rates that were not significantly different at birth and 6 months. However the reduction in risk of HIV infection or death at 6 months was marginally significant (Efficacy 45.00%; 95% CI -4.00 to 94.00).Antiretroviral regimens using different drugs and durations of treatmentIn breastfeeding populations, three trials found that:A single dose of NVP given to mothers at the onset of labour plus a single dose of NVP given to their babies immediately after birth ('HIVNET 012 regimen') compared with ZDV given to mothers during labour and to their babies for a week after birth resulted in lower HIV infection rates at 4-8 weeks (Efficacy 41.00%; 95% CI 11.84 to 70.16), 3-4 months (Efficacy 38.91%; 95% CI 11.24 to 66.58), 12 months (Efficacy 35.98 [9.25, 62.71]36.00%; 95% CI 8.56 to 63.44) and 18 months (Efficacy 39.15%; 95% CI 13.81 to 64.49). In addition, the NVP regimen significantly reduced the risk of HIV infection or death at 4-8 weeks (Efficacy 41.74%; 95% CI 14.30 to 69.18), 3 to 4 months (Efficacy 40.00%; 95% CI 14.34 to 65.66), 12 months (Efficacy 32.17%; 95% CI 8.51 to 55.83) and 18 months (Efficacy 32.57 [9.93, 55.21]33.00%; 95% CI 9.93 to 55.21).The 'HIVNET 012 regimen' plus ZDV given to babies for 1 week after birth compared with the 'HIVNET 012 regimen' alone did not result in a statistically significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth plus ZDV given to babies for 1 week after birth compared with a single dose of NVP given to babies only significantly reduced the HIV infection rate at 4 to 8 weeks (Efficacy 36.79%; 95% CI 3.57 to 70.01).Five trials in non-breastfeeding populations found that:In a population in which mothers were receiving 'standard' antiretroviral for HIV infection a single dose of NVP given to mothers in labour plus a single dose of NVP given to babies immediately after birth ('HIVNET 012 regimen') compared with placebo did not result in a statistically significant difference in HIV infection rates at birth and at 4 to 8 weeks.The 'Thai CDC regimen' compared with the 'HIVNET 012 regimen' did not result in a significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth compared to ZDV given to babies for the first 6 weeks after birth did not result in a significant difference in HIV infection rates at 4-8 weeks and 3 to 4 months. (ABSTRACT TRUNCATED)

Genital tract, cord blood, and amniotic fluid exposures of seven antiretroviral drugs during and after pregnancy in human immunodeficiency virus type 1-infected women

The objective of the study was to measure antiretroviral exposures in four physiological compartments during pregnancy, delivery, and postpartum. This prospective, open-label, longitudinal study collected paired blood plasma (BP) and genital tract (GT) aspirates antepartum, at delivery, and up to 12 weeks postpartum. Antiretroviral cord BP and amniotic fluid concentrations were also measured. Drug concentrations were analyzed by validated high-performance liquid chromatography/UV and liquid chromatography/tandem mass spectrometry methods, with secondary compartment concentrations presented as the percentage of BP. Fourteen women taking lamivudine plus zidovudine and either lopinavir-ritonavir (n = 7), nelfinavir (n = 6), or nevirapine (n = 1) were enrolled; four also received tenofovir. GT penetration relative to BP was highest for the nucleoside reverse transcriptase inhibitors compared to the protease inhibitors and nevirapine. Only antepartum nelfinavir GT penetration was significantly higher than in the second trimester (geometric mean ratio [GMR], 179.3) or third trimester (GMR, 41.9). Compared to nonpregnant historical controls, antepartum GT penetration was significantly lower (P < 0.05) for zidovudine (GMR, 0.25) and lopinavir (GMR, 0.03); postpartum lopinavir GT penetration continued to be significantly lower (GMR, 0.27). Cord BP exposures were highest for lamivudine and tenofovir (> or = 100%), with cord BP levels of the remaining drugs ranging from 49 to 86% of that of the respective BP level. Amniotic exposures for lamivudine, zidovudine, tenofovir, and nelfinavir were > or = 100%, nevirapine exposure was 53%, and lopinavir and ritonavir exposures were < or = 6% that of BP. We conclude that GT, cord BP, and amniotic fluid exposures vary within and between antiretroviral drug classes and biologic sites. Measurement of antiretroviral exposure in maternal genital secretions, cord BP, and amniotic fluid may be needed to identify signals of subtherapeutic or supratherapeutic drug exposure.

Pharmacokinetics of oral zidovudine administered during labour: a preliminary study

OBJECTIVES

The aim of this study was to determine whether oral zidovudine (ZDV) given during labour would provide a similar systemic exposure to the established intravenous regimen used to prevent mother-to-child transmission in HIV-infected pregnant women.

METHODS

ZDV pharmacokinetic parameters following oral administration during labour were determined in 10 HIV-infected pregnant women in active labour. All subjects were converted to intravenous ZDV prior to delivery.

RESULTS

In cohort 1 (n=6), subjects received 300 mg oral ZDV every 3 h for three doses. Oral therapy was well tolerated but plasma ZDV concentrations were substantially lower than previously reported with continuous intravenous therapy. Based on the pharmacokinetic results from cohort 1, women in cohort 2 (n=4) received an initial 600 mg dose followed by two 400 mg doses every 3 h. ZDV area under the curve and concentrations in cohort 2 increased approximately in proportion to the increase in dose but varied 6-7-fold. In both cohorts, ZDV pharmacokinetic parameters suggested erratic absorption.

CONCLUSIONS

While ZDV exposure improved with the increased dosing regimen, our sample size was small and larger studies are needed to establish whether oral ZDV administration during labour can consistently provide equivalent exposure to intravenous administration.

Monitoring and evaluation of programmes to prevent mother to child transmission of HIV in Africa

Many countries are expanding the coverage of programmes to prevent mother to child transmission of HIV. Although the need is unquestionable, Richard Reithinger and colleagues are concerned that without true measures of effectiveness we may not be making the best use of resources

Antiretrovirals for reducing the risk of mother-to-child transmission of HIV infection

BACKGROUND

Antiretroviral drugs (ARV) reduce viral replication and can reduce mother-to-child transmission of HIV either by lowing plasma viral load in pregnant women or through post-exposure prophylaxis in their newborns. In rich countries, highly active antiretroviral therapy (HAART) has reduced the vertical transmission rates to around 1-2%, but HAART is not yet widely available in low and middle income countries. In these countries, various simpler and less costly antiretroviral regimens have been offered to pregnant women or to their newborn babies, or to both.

OBJECTIVES

To determine whether, and to what extent, antiretroviral regimens aimed at decreasing the risk of mother-to-child transmission of HIV infection achieve a clinically useful decrease in transmission risk, and what effect these interventions have on maternal and infant mortality and morbidity.

SEARCH STRATEGY

We sought to identify all relevant studies regardless of language or publication status by searching the Cochrane HIV/AIDS Review Group Trials Register, The Cochrane Library, Medline, EMBASE and AIDSearch and relevant conference abstracts. We also contacted research organizations and experts in the field for unpublished and ongoing studies. The original review search strategy was updated in 2006.

SELECTION CRITERIA

Randomised controlled trials of any antiretroviral regimen aimed at decreasing the risk of mother-to-child transmission of HIV infection compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected relevant studies, extracted data and assessed trial quality. For the primary outcomes, we used survival analysis to estimate the probability of infants being infected with HIV (the observed proportion) at various specific time-points and calculated efficacy at a specific time as the relative reduction in the proportion infected. Efficacy, at a specific time, is defined as the preventive fraction in the exposed group compared to the reference group, which is the relative reduction in the proportion infected: 1-(Re/Rf). For those studies where efficacy and hence confidence intervals were not calculated, we calculated the approximate confidence intervals for the efficacy using recommended methods. For analysis of results that are not based on survival analyses we present the relative risk for each trial outcome based on the number randomised. No meta-analysis was conducted as no trial assessed the identical drug regimens.

MAIN RESULTS

Eighteen trials including 14,398 participants conducted in 16 countries were eligible for inclusion in the review. The first trial began in April 1991 and assessed zidovudine (ZDV) versus placebo and since then, the type, dosage and duration of drugs to be compared has been modified in each subsequent trial. Antiretrovirals versus placebo In breastfeeding populations, three trials found that:ZDV given to mothers from 36 to 38 weeks gestation, during labour and for 7 days after delivery significantly reduced HIV infection at 4-8 weeks (Efficacy 32.00%; 95% CI 0.64 to 63.36), 3 to 4 months (Efficacy 34.00%; 95% CI 6.56 to 61.44), 6 months (Efficacy 35.00%; 95% CI 9.52 to 60.48), 12 months (Efficacy 34.00%; 95% CI 8.52 to 59.48) and 18 months (Efficacy 30.00%; 95% CI 2.56 to 57.44).ZDV given to mothers from 36 weeks gestation and during labour significantly reduced HIV infection at 4 to 8 weeks (Efficacy 44.00%; 95% CI 8.72 to 79.28) and 3 to 4 months (Efficacy 37.00%; 95% CI 3.68 to 70.32) but not at birth.ZDV plus lamivudine (3TC) given to mothers from 36 weeks gestation, during labour and for 7 days after delivery and to babies for the first 7 days of life (PETRA 'regimen A') significantly reduced HIV infection (Efficacy 63.00%; 95% CI 41.44 to 84.56) and a combined endpoint of HIV infection or death (Efficacy 61.00%; 95% CI 41.40 to 80.60) at 4 to 8 weeks but these effects were not sustained at 18 months.ZDV plus 3TC given to mothers from the start of labour until 7 days after delivery and to babies for the first 7 days of life (PETRA 'regimen B') significantly reduced HIV infection (Efficacy 42.00%; 95% CI 12.60 to 71.40) and HIV infection or death at 4 to 8 weeks (Efficacy 36.00%; 95% CI 8.56 to 63.44) but the effects were not sustained at 18 months.ZDV plus 3TC given to mothers during labour only (PETRA 'regimen C') with no treatment to babies did not reduce the risk of HIV infection at either 4 to 8 weeks or 18 months. In non-breastfeeding populations, three trials found that:ZDV given to mothers from 14 to 34 weeks gestation and during labour and to babies for the first 6 weeks of life significantly reduced HIV infection in babies at 18 months (Efficacy 66.00%; 95% CI 34.64 to 97.36).ZDV given to mothers from 36 weeks gestation and during labour with no treatment to babies ('Thai-CDC regimen') significantly reduced HIV infection at 4 to 8 weeks (Efficacy 50.00%; 95% CI 12.76 to 87.24) but not at birthZDV given to mothers from 38 weeks gestation and during labour with no treatment to babies did not influence HIV transmission at 6 months. Longer versus shorter regimens using the same antiretrovirals One trial in a breastfeeding population found that:ZDV given to mothers during labour and to their babies for the first 3 days of life compared with ZDV given to mothers from 36 weeks and during labour (similar to 'Thai-CDC') resulted in HIV infection rates that were not significantly different at birth, 4-8 weeks, 3 to 4 months, 6 months and 12 months. Three trials in non-breastfeeding populations found that:ZDV given to mothers from 28 weeks gestation during labour and to infants for the first 3 days after birth compared with ZDV given to mothers from 35 weeks gestation through labour and to infants from birth to 6 weeks significantly reduced HIV infection rate at 6 months (Efficacy 45.00%; 95% CI 1.88 to 88.12) but compared with the same regimen ZDV given to mothers from 28 weeks gestation through labour and to infants from birth to 6 weeks did not result in a statistically significant difference in HIV infection at 6 months. ZDV given to mothers from 35 weeks gestation during labour and to infants for the first 3 days after birth was considered ineffective for reducing transmission rates and this regimen was discontinued.An antenatal/intrapartum course of ZDV used for a median of 76 days compared with an antenatal/intrapartum ZDV regimen used for a median 28 days with no treatment to babies in either group did not result in HIV infection rates that were significantly different at birth and at 3 to 4 months. In a programme where mothers were routinely receiving ZDV in the third trimester of pregnancy and babies were receiving one week of ZDV therapy, a single dose of nevirapine (NVP) given to mothers in labour and to their babies soon after birth compared with a single dose of NVP given to mothers only resulted in HIV infection rates that were not significantly different at birth and 6 months. However the reduction in risk of HIV infection or death at 6 months was marginally significant (Efficacy 45.00%; 95% CI -4.00 to 94.00). Antiretroviral regimens using different drugs and durations of treatment In breastfeeding populations, three trials found that:A single dose of NVP given to mothers at the onset of labour plus a single dose of NVP given to their babies immediately after birth ('HIVNET 012 regimen') compared with ZDV given to mothers during labour and to their babies for a week after birth resulted in lower HIV infection rates at 4-8 weeks (Efficacy 41.00%; 95% CI 11.60 to 70.40), 3-4 months (Efficacy 39.00%; 95% CI 11.56 to 66.44), 12 months (Efficacy 36.00%; 95% CI 8.56 to 63.44) and 18 months (Efficacy 39.00%; 95% CI 13.52 to 64.48). In addition, the NVP regimen significantly reduced the risk of HIV infection or death at 4-8 weeks (Efficacy 42.00%; 95% CI 14.56 to 69.44), 3 to 4 months (Efficacy 40.00%; 95% CI 14.52 to 65.48), 12 months (Efficacy 32.00%; 95% CI 8.48 to 55.52) and 18 months (Efficacy 33.00%; 95% CI 9.48 to 56.52). The 'HIVNET 012 regimen' plus ZDV given to babies for 1 week after birth compared with the 'HIVNET 012 regimen' alone did not result in a statistically significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth plus ZDV given to babies for 1 week after birth compared with a single dose of NVP given to babies only significantly reduced the HIV infection rate at 4 to 8 weeks (Efficacy 37.00%; 95% CI 3.68 to 70.32). Five trials in non-breastfeeding populations found that:In a population in which mothers were receiving 'standard' ARV for HIV infection a single dose of NVP given to mothers in labour plus a single dose of NVP given to babies immediately after birth ('HIVNET 012 regimen') compared with placebo did not result in a statistically significant difference in HIV infection rates at birth and at 4 to 8 weeks. The 'Thai CDC regimen' compared with the 'HIVNET 012 regimen' did not result in a significant difference in HIV infection at 4 to 8 weeks.A single dose of NVP given to babies immediately after birth compared to ZDV given to babies for the first 6 weeks of life did not result in a significant difference in HIV infection rates at 4-8 weeks and 3 to 4 months.ZDV plus 3TC given to mothers in labour and for a week after delivery and to their infants for a week after birth (similar to 'PETRA regimen B') compared with NVP given to mothers in labour and immediately after delivery plus a single dose of NVP to their babies immediately after birth (similar to 'HIVNET 012 regimen') did not result in a significant difference in the HIV infection rate at 4 to 8 weeks. (ABSTRACT TRUNCATED)

Biological mechanisms of vertical human immunodeficiency virus (HIV-1) transmission

In the absence of interventions, 30-45% of exposed infants acquire human immunodeficiency virus type 1 (HIV-1) through mother-to-child transmission. It remains unclear why some infants become infected while others do not, despite significant exposure to HIV-1 in utero, during delivery and while breastfeeding. Here we discuss the correlates of vertical transmission with an emphasis on factors that increase maternal HIV-1 levels, either systemically or locally in genital secretions and breast milk. Immune responses may influence maternal viral load, and data suggest that maternal neutralising antibodies reduce infection rates. In addition, infants may be capable of mounting HIV-specific cellular immune responses. We propose that both humoral and cellular responses are necessary to reduce infection because cell-free as well as cell-associated virus appears to play a role in vertical transmission. These distinct forms of the virus may be targeted most effectively by different components of the immune system. We also discuss the use of antiretrovirals to reduce transmission, focusing on the mechanisms of action of regimens currently used in developing country settings. We conclude that prevention relies not only on reducing maternal HIV-1 levels within blood, genital tract and breast milk, but also on pre- and/or post-exposure prophylaxis to the infant. However, HIV-1 has the capacity to mutate under drug pressure and rapidly acquires mutations conferring antiretroviral resistance. This review concludes with data on persistence of low-level resistance after delivery as well as recent guidelines for maternal and infant regimens designed to limit resistance.

Transfer of antivirals across the human placenta

BACKGROUND

Viruses cross the placenta and infect the fetus. Antivirals are administered to pregnant women to protect them and the fetus against the viruses. It is necessary to know which antivirals cross the placenta and reach the fetal circulation in pharmacologically significant concentrations in order to plan antiviral therapy.

AIMS

This article reviews the literature on the placental transfer of antivirals against HIV. The review considers also the placental transfer of acyclovir and ganciclovir, which are used against the herpes simplex virus and the cytomegalovirus, respectively.

STUDY DESIGN

Firstly, a medline was performed with the following key words "placental transfer of antivirals". Secondly, a medline was performed with the key words "placenta transfer of..." followed by the name of a single antiviral and it was repeated for 20 antivirals. Thirdly, another medline was performed using the following key words "pharmacokinetics of antiviral in newborn" in order to collect those articles which describe in vivo transfer of antivirals. The literature was critically read and a written note was produced.

RESULTS

The literature on the placental transfer of antivirals includes studies in vitro perfusing the human placenta and studies performed in vivo in which the cord and maternal antiviral plasma concentrations are compared. Both the results obtained in vitro and in vivo show that the protease inhibitors poorly transfer the placenta because of their great molecular weight. With the exception of didanosine, the nucleoside reverse transcriptase inhibitors and nelfinavir, a non-nucleoside reverse transcriptase inhibitor, cross the placenta and the cord, and maternal plasma concentrations equilibrate.

CONCLUSIONS

In vitro and in vivo results are consistent with the view that the nucleoside reverse transcriptase inhibitors cross the human placenta and produce significant pharmacological concentrations in the fetal circulation. Nevirapine, the only studied non-nucleoside reverse transcriptase inhibitor, reach the equilibrium between the fetal and maternal concentration, whereas the protease inhibitors have a poor transfer across the human placenta.

Pharmacotherapy of perinatal HIV

Continued spread of HIV infection among women has led to the use of antiretrovirals in pregnant women and their newborns. Regional strategies to prevent mother-to-child transmission are evolving. Altered drug disposition during pregnancy may require altered dosing or 'boosted' therapies to avoid treatment failure. Maturing drug elimination pathways in newborns must also be considered for effective therapy. Potential teratogenic effects and increased sensitivity to antiretroviral toxicities might be encountered in this population. Use of highly active antiretroviral therapy (HAART) to suppress viral replication combined with formula feeding can reduce the rate of mother-to-child HIV transmission to less than 2%. In resource-limited settings, less intensive regimens including zidovudine, lamivudine and nevirapine still substantially reduce mother-to-child transmission. Although difficult to perform, clinical trials to determine the safety, pharmacokinetics and optimal dosing of antiretroviral in pregnant women and their newborns are urgently needed.

Pharmacokinetics of Antiretrovirals in Pregnant Women

Antiretroviral treatment of HIV-infected pregnant women is widely used to prevent mother-to-child HIV transmission and as primary therapy of maternal HIV infection. The physiological changes associated with pregnancy have a large impact on drug disposition, and changes in antiretroviral pharmacokinetics during pregnancy must be understood for these drugs to be used safely and effectively in pregnant women. Zidovudine and didanosine, two of the nucleoside reverse transcriptase inhibitors, demonstrate an increase in clearance and decrease in area under the concentration-time curve during pregnancy. The clinical significance of these changes is unknown due to the lack of a clear relationship between plasma concentrations of nucleoside reverse transcriptase inhibitors and clinical effects. Pharmacokinetic parameters of lamivudine, stavudine and abacavir are not significantly changed during pregnancy. There are no data describing the effect of pregnancy on the pharmacokinetics of the other nucleoside/nucleotide analogues (zalcitabine, emtricitabine and tenofovir). Pregnancy does not appear to have a significant effect on the pharmacokinetics of the non-nucleoside reverse transcriptase inhibitor nevirapine and there are no data describing the pharmacokinetics of the other non-nucleoside reverse transcriptase inhibitors (efavirenz and delavirdine) during pregnancy. Reduced plasma concentrations during pregnancy have been described for several of the protease inhibitors, including nelfinavir (with administration of 750 mg three times daily), indinavir, saquinavir and Kaletra (a co-formulation of lopinavir and ritonavir). Plasma concentrations equivalent to those in nonpregnant adults have been reported in pregnant women receiving nelfinavir at doses of 1250 mg twice daily, and the addition of ritonavir to saquinavir greatly increases saquinavir exposure to therapeutic concentrations in pregnant women. No pregnancy pharmacokinetic data are available for the newer protease inhibitors atazanavir and fosamprenavir, or with other dual protease inhibitor combinations that include low dose ritonavir to boost concentrations of the coadministered protease inhibitor. Further investigations of antiretroviral pharmacology during pregnancy, including protein binding studies, are urgently needed.

Zidovudine: a review of its use in the management of vertically-acquired pediatric HIV infection

Zidovudine is a thymidine analog that, after intracellular phosphorylation to zidovudine triphosphate metabolite, inhibits HIV-specific reverse transcriptase and terminates proviral DNA. Zidovudine administered to mildly symptomatic women with HIV infection in the antepartum (100mg orally 5 times/day), intrapartum (2 mg/kg intravenously over 1 hour then 1 mg/kg/h) and then to the neonate for 6 weeks (2 mg/kg), significantly reduced the rate of vertical HIV transmission by about two thirds, in the absence of breast-feeding (The Pediatric AIDS Clinical Trials Group 076 trial, standard protocol). Shorter zidovudine regimens, reduced the risk of transmission of HIV by 50% in a non-breast-feeding population and by about 37% in breast-feeding populations. Zidovudine (standard protocol) in combination with lamivudine was superior to zidovudine alone. A short oral zidovudine regimen was not as effective as a two-dose oral nevirapine regime, although the combination of short-course zidovudine plus lamivudine was as effective. Suppression of viral replication in neonates, infants and children has been achieved with zidovudine when used in triple-therapy regimens that include other antiviral drugs. Results from a trial of treatment-naive children indicate that the antiviral efficacy of combinations of zidovudine and lamivudine or abacavir, given with the protease inhibitor nelfinavir, is superior to treatment with this combination minus nelfinavir. When zidovudine was used in other highly active antiretroviral therapy regimens significant improvements in surrogate markers were consistently seen. Changing to ritonavir-containing regimens was superior to changing to treatment with two new nucleoside reverse transcriptase inhibitors. Short- and long-term (up to 5.6 years) outcomes from clinical trials showed that prenatal and neonatal exposure to zidovudine was generally well tolerated with the exception of mild anemia that resolved spontaneously after treatment cessation. Zidovudine was generally well tolerated as monotherapy in clinical trials of pediatric patients with HIV infection, and adverse events were similar to those reported in adults, with anemia and neutropenia being the most common.

CONCLUSION

Zidovudine, as monotherapy or in combination with other antiretroviral agents, remains a first-choice therapy for the prophylaxis of mother-to-child HIV transmission as shown by substantial reductions in transmission rates. Where feasible, the optimal strategy to prevent vertical transmission is to combine drug therapy with Cesarean section delivery and no breast-feeding. In addition, zidovudine in combination with another nucleoside analogue and a protease inhibitor is a first- or second-choice therapy for the treatment of pediatric HIV infection as significant and sustained reductions in viral load have been shown in both plasma and cerebrospinal fluid.

Antiretrovirals for reducing the risk of mother-to-child transmission of HIV infection

BACKGROUND

At the end of 2000 it was estimated that over 36 million people were living with the human immunodeficiency virus (HIV). This includes 1.4 million children less than 15 years of age. This is one of several reviews assessing the available evidence for preventing mother-to-child transmission of HIV infection. The other reviews will address other interventions, including Caesarean section, breast feeding, vaginal lavage and vitamin A supplementation.

OBJECTIVES

To assess which antiretroviral therapies may be effective in decreasing the risk of mother-to-child transmission of HIV infection as well as their effect on neonatal and maternal mortality and morbidity.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register. We also searched conference abstracts from the International AIDS Conferences and Conference on Retroviruses and Opportunistic Infections.

SELECTION CRITERIA

Randomised trials comparing any antiretroviral therapy aimed at decreasing the risk of mother-to-child transmission of HIV infection with placebo or no treatment, or any two or more antiretroviral therapies or regimens aimed at decreasing the risk of mother-to-child transmission of HIV infection.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality.

MAIN RESULTS

Zidovudine monotherapy Any zidovudine regimen versus placebo significantly reduces the risk of mother-to-child transmission (Peto odds ratio (OR) 0.46, 95% confidence interval (CI) 0.35 to 0.60). Zidovudine also appears to decrease the risk of infant death within the first year of birth (OR 0.57, 95% CI 0.38 to 0.85) and the risk of maternal death (OR 0.32, 95% CI 0.16 to 0.66). There is no evidence that zidovudine influences the incidence of premature delivery (OR 0.86, 95% CI 0.57 to 1.29) or low birth weight (OR 0.74, 95% CI 0.53 to 1.04). The risk of transmission using a 'short-short' course of zidovudine (from 35 weeks in pregnancy for the mother and for the baby until 3 days old) was higher than the risk using a 'long-long' course (from 28 weeks in pregnancy for the mother and for the baby until 6 weeks old), (OR 2.55, 95% CI 1.26 to 5.18). However, the effectiveness of the 'long-short' course (from 28 weeks in pregnancy for the mother and for the baby until 3 days old) and the 'short-long' course (from 35 weeks in pregnancy for the mother and for the baby until 6 weeks old) did not differ from that of the 'long-long' course. Nevirapine One large randomised controlled trial demonstrates that nevirapine given to mothers as a single dose at the onset of labour and to babies as a single dose within 72 hours of birth is more effective than an intrapartum and post-partum regimen of zidovudine (OR 0.51, 95% CI 0.33 to 0.79). When nevirapine is given to mothers already receiving standard antiretroviral therapy, however, there appears to be no additional advantage (OR 1.10, 95% CI 0.42 to 2.86). Combination Therapy Preliminary findings of the effect of combination therapy using zidovudine and lamivudine (3TC) suggest a decrease in the risk of transmission when the combination is given during the antenatal and intrapartum period or during the intrapartum and postpartum period compared with placebo. There is no evidence that intrapartum zidovudine and lamivudine alone are sufficient to decrease the risk of transmission compared with placebo.

REVIEWER'S CONCLUSIONS

Implications for practice The randomised trials included in this review provide evidence that short course zidovudine and single-dose nevirapine are effective therapies for reducing mother-to-child transmission of HIV. The challenge for low and middle income countries will be to institute this therapy in practice. In industrialised countries practice has already moved on from the current evidence and combination antiretroviral therapy aimed primarily at preventing disease progression in the mother is the standard of care. Implications for research The potential value of nevirapine used for longer durations in breastfeeding populations should be considered as it may further reduce the risk of mother-to-child transmission, particularly if combined with early weaning. On-going evaluation of combination antiretroviral therapy is essential and will have an immediate benefit for countries with the resources to adopt such treatment. The search for effective, affordable, safe and acceptable alternatives to antiretroviral therapy for reducing mother-to-child transmission in resource poor countries should remain on the research agenda.

Design of antiretroviral clinical trials for HIV-1 infected pregnant women and their newborn infants

Antiretroviral therapy has been highly successful in reducing mother to child transmission of human immunodeficiency virus-1 infection in pregnant women. However, the treatment regimens are intensive, difficult to deliver in less developed countries, and there are limited pharmacology studies addressing critical questions regarding maternal safety and fetal risk. There are currently 3 pharmacologically diverse classes of antiretroviral agents with inadequate information available to define drug disposition necessary to determine appropriate dose regimens and limited data on long-term adverse events. This article summarizes representative clinical studies for selected antiretrovirals that provide a framework for continuing the necessary clinical research to extend successful outcomes in developed countries to human immunodeficiency virus-1 infected pregnant women and infants world-wide and minimize the risk of long-term adverse effects.