Pharmacokinetics of nevirapine in HIV-infected children receiving an adult fixed-dose combination of stavudine, lamivudine and nevirapine

An analysis of volumes, prices and pricing trends of the pediatric antiretroviral market in developing countries from 2004 to 2012

BACKGROUND

The pediatric antiretroviral (ARV) market is poorly described in the literature, resulting in gaps in understanding treatment access. We analyzed the pediatric ARV market from 2004 to 2012 and assessed pricing trends and associated factors.

METHODS

Data on donor funded procurements of pediatric ARV formulations reported to the Global Price Reporting Mechanism database from 2004 to 2012 were analyzed. Outcomes of interest were the volume and mean price per patient-year ARV formulation based on WHO ARV dosing recommendations for a 10 kg child. Factors associated with the price of formulations were assessed using linear regression; potential predictors included: country income classification, geographical region, market segment (originator versus generic ARVs), and number of manufacturers per formulation. All analyses were adjusted for type of formulations (single, dual or triple fixed-dose combinations (FDCs))

RESULTS

Data from 111 countries from 2004 to 2012 were included, with procurement of 33 formulations at a total value of USD 204 million. Use of dual and triple FDC formulations increased substantially over time, but with limited changes in price. Upon multivariate analysis, prices of originator formulations were found to be on average 72 % higher than generics (p < 0.001). A 10 % increase in procurement volume was associated with a 1 % decrease (p < 0.001) in both originator and generic prices. The entry of one additional manufacturer producing a formulation was associated with a decrease in prices of 2 % (p < 0.001) and 8 % (p < 0.001) for originator and generic formulations, respectively. The mean generic ARV price did not differ by country income level. Prices of originator ARVs were 48 % (p < 0.001) and 14 % (p < 0.001) higher in upper-middle income and lower-middle income countries compared to low income countries respectively, with the exception of South Africa, which had lower prices despite being an upper-middle income country.

CONCLUSIONS

The donor funded pediatric ARV market as represented by the GPRM database is small, and lacks price competition. It is dominated by generic drugs due to the lower prices offered and the practicality of FDC formulations. This market requires continued donor support and the current initiatives to protect it are important to ensure market viability, especially if new formulations are to be introduced in the future.

Pharmacokinetics of nevirapine, stavudine and lamivudine in Indian HIV-infected children receiving generic fixed dose combinations

OBJECTIVE

To determine the trough and two hour plasma levels of nevirapine, stavudine, and lamivudine when administered in fixed dose combinations (FDC).

DESIGN

Cross sectional.

SETTING

Tertiary care hospital in Northern India.

PARTICIPANTS

79 HIV-infected children receiving antiretroviral therapy with FDCs for more than month.

INTERVENTION

Two-point sampling (0 and 2 hours after the morning dose).

OUTCOME MEASURES

Plasma concentrations of all three drugs were simultaneously assayed by liquid chromatography/mass spectroscopy.

RESULTS

Majority (77%) of children were receiving fixed dose combination of stavudine, lamivudine, nevirapine in the ratio of 6:30:50 mg. The median (IQR) trough and 2-hour plasma levels (µg/mL) of nevirapine, stavudine and lamivudine were 5.2 (4.0, 6.3) and 7.9 (6.0, 9.7); 0.1 (0.06, 0.16) and 1.1 (0.59, 1.6); 0.1 (0.02, 0.2) and 2.5 (1.4, 3.1), respectively. Very few children had sub-therapeutic plasma drug levels of stavudine (2.5%), lamivudine (7.6%) and nevirapine (10%). Inadequate viral suppression at 6 months follow up was significantly associated with initial high viral load, low CD4 percentage at the time of enrolment in study, and lower doses of lamivudine and stavudine.

CONCLUSIONS

The currently available generic pediatric fixed dose antiretroviral combinations in India provide adequate drug exposure in majority of children.

Impact of adherence and anthropometric characteristics on nevirapine pharmacokinetics and exposure among HIV-infected Kenyan children

BACKGROUND

There are insufficient data on pediatric antiretroviral therapy (ART) pharmacokinetics (PK), particularly for children in low- and middle-income countries.

METHODS

We conducted a prospective nevirapine (NVP) PK study among HIV-infected Kenyan children aged 3-13 years initiating an NVP-based ART regimen. NVP dose timing was measured through medication event monitors. Participants underwent 2 inpatient assessments: 1 at 4-8 weeks after ART initiation and 1 at 3-4 months after ART initiation. Allometric scaling of oral clearance (CL)/bioavailability (F) and volume of distribution (Vd)/F values were computed. Nonlinear mixed-effects modeling using the first-order conditional estimation with interaction method was performed with covariates. The impact of adherence on time below minimum effective concentration was assessed in the final PK model using medication event monitors data and model-estimated individual parameters.

RESULTS

Among 21 children enrolled, mean age was 5.4 years and 57% were female. CL/F was 1.67 L/h and Vd/F was 3.8 L for a median child weighing 15 kg. Participants' age had a significant impact on CL/F (P < 0.05), with an estimated decrease in CL of 6.2% for each 1-year increase in age. Total body water percentage was significantly associated with Vd/F (P < 0.001). No children had >10% of time below minimum effective concentration when the PK model assumed perfect adherence compared with 10 children when adherence data were used.

CONCLUSIONS

Age and body composition were significantly associated with children's NVP PK parameters. ART adherence significantly impacted drug exposure over time, revealing subtherapeutic windows that may lead to viral resistance.

Evaluation of nevirapine dosing recommendations in HIV-infected children

AIMS

Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor used for chronic human immunodeficiency virus infections in adults and children. The aims of this study were to investigate the population pharmacokinetics of NVP in children, establish factors that influence NVP pharmacokinetics and evaluate the current dosing recommendations.

METHODS

Concentrations were measured on a routine basis in 94 children aged from 2 months to 17 years. A total of 390 NVP plasma concentrations were retrospectively collected, and a population pharmacokinetic model was developed with Monolix 4.0.

RESULTS

Nevirapine pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. After standardization to a 70 kg adult using allometry, postmenstrual age had a significant effect on the bioavailability. Estimates of apparent clearance and volume of distribution were 3.9 l h(-1) (70 kg)(-1) and 140 l (70 kg)(-1) , respectively. Based on simulations of European Medicines Agency (EMA) and World Health Organization (WHO) dosing recommendations, the probability of observing minimal concentrations below the efficacy target of 3 mg l(-1) is higher following the EMA recommendations than the WHO recommendations. However, NVP underdosing persists for the 3-6 and 6-10 kg weight ranges following the WHO recommendations.

CONCLUSIONS

It is suggested to increase doses to 75 and 100 mg twice daily for the 3-6 and 6-10 kg weight ranges, respectively, in order to obtain more than 95% of children with concentrations above 3 mg l(-1) .

Five-year trends in antiretroviral usage and drug costs in HIV-infected children in Thailand

BACKGROUND

As antiretroviral treatment (ART) programs mature, data on drug utilization and costs are needed to assess durability of treatments and inform program planning.

METHODS

Children initiating ART were followed up in an observational cohort in Thailand. Treatment histories from 1999 to 2009 were reviewed. Treatment changes were categorized as: drug substitution (within class), switch across drug class (non nucleoside reverse-transcriptase inhibitors (NNRTI) to/from protease inhibitor (PI)), and to salvage therapy (dual PI or PI and NNRTI). Antiretroviral drug costs were calculated in 6-month cycles (US$ 2009 prices). Predictors of high drug cost including characteristics at start of ART (baseline), initial regimen, treatment change, and duration on ART were assessed using mixed-effects regression models.

RESULTS

Five hundred seven children initiated ART with a median 54 (interquartile range, 36-72) months of follow-up. Fifty-two percent had a drug substitution, 21% switched across class, and 2% to salvage therapy. When allowing for drug substitution, 78% remained on their initial regimen. Mean drug cost increased from $251 to $428 per child per year in the first and fifth year of therapy, respectively. PI-based and salvage regimens accounted for 16% and 2% of treatments prescribed and 33% and 5% of total costs, respectively. Predictors of high cost include baseline age ≥ 8 years, non nevirapine-based initial regimen, switch across drug class, and to salvage regimen (P < 0.005).

CONCLUSIONS

At 5 years, 21% of children switched across drug class and 2% received salvage therapy. The mean drug cost increased by 70%. Access to affordable second- and third-line drugs is essential for the sustainability of treatment programs.

Antiretroviral therapy for children: challenges and opportunities

Currently, <10% of all HIV-infected children who need anti-retroviral therapy in sub-Saharan Africa are actually receiving therapy. Many constraints prevent these children from gaining access to appropriate care, including the magnitude of the paediatric epidemic, competing interests of adult care, health system inadequacies, technical challenges and patient-related factors. These issues form the basis of this paper which discusses the practical challenges of extending optimal care to all deserving children. Besides the need for major human, infrastructural, technical and logistic investments to overcome existing constraints, more clinical research is required before treatment guidelines can be refined in resource-constrained settings. In this regard, the paper lists some important research questions that should be addressed.

Paediatric HIV infection in Western Africa: the long way to the standard of care

In sub-Saharan Africa, newborns and children continue to suffer from insufficient access to early diagnosis and antiretroviral (ARV) treatments. A survey had been conducted in Burkina Faso, Ghana and Ivory Coast, from January 2010 to February 2011 to identify the major challenges regarding HIV prophylaxis and treatment of children in western Africa. The results of this survey highlight that only a small proportion of HIV-exposed newborns receive ARV prophylaxis. However, this problem is often not perceived at the national level. The problem could be faced by improving the communication process between the peripheral health services and the national procurement system. Moreover, supporting the development of local pharmaceutical industries could facilitate the availability of child-sized drugs, contextualized to the socio-cultural needs of such area, adequate not only in terms of efficacy, safety and tolerability, but also in terms of palatability, storage, distribution and cost.

How can we simplify antiretroviral therapy in children?

PURPOSE OF REVIEW

The aim of this article is to present approaches towards simplifying pediatric antiretroviral therapy in order to improve access to care, coverage of HIV-positive children, and support adherence to treatment.

RECENT FINDINGS

Barriers to rapid and effective global scale-up of pediatric antiretroviral therapy include the narrow range of available pediatric antiretrovirals, complicated dosing schedules, and social and economic instability of the family caused by poverty, stigma, and death. Healthcare providers can simplify antiretroviral therapy delivery by promoting the development and use of pediatric fixed dose combinations and scored adult antiretrovirals, using weight-band dosing tables to prescribe antiretrovirals, and identifying less complex regimens. Caretakers would benefit from active counseling to facilitate more open communication with their children about adherence and disclosure. Children can develop long-term coping strategies through learning life skills that build confidence and improve decision-making. Whenever possible, antiretroviral therapy programs should provide access to free antiretrovirals, identify funds to cover transportation costs, and refer families to available community support programs.

SUMMARY

Interventions to simplify the administration of antiretroviral therapy need to address not only how antiretrovirals are prescribed and formulated, but the relationships of HIV-positive children with their families and communities as well.

The long-term effectiveness of generic adult fixed-dose combination antiretroviral therapy for HIV-infected Ugandan children

BACKGROUND

Access to pediatric antiretroviral formulations is increasing in resource-limited countries, however adult FDCs are still commonly used by antiretroviral therapy (ART) programs.

OBJECTIVE

To describe long-term effectiveness of using adult FDC of d4T+3TC+NVP (Triomune) in children for HIV treatment.

METHODS

Clinical, immunologic, and virologic outcomes of HIV-infected ART-naïve children aged six months to 12 years, were evaluated up to 96 weeks post-ART initiation.

RESULTS

From March 2004 to June 2006, 104 children were followed with a median age of 5.4 years, median CD4 cell percent and HIV-1 RNA were 11.0% (IQR 6.7-13.9) and 348,846copies/mL (IQR 160,941-681,313) respectively at baseline. Using Kaplan-Meir estimates, 75% of children had undetectable viral loads (<400copies/mL) at 96 weeks of ART. Children with a baseline CD4 cell percent >15% were 3 times more likely to achieve viral load <400copies/mL than those with baseline CD4 cell percent <5% after adjusting for baseline age {aHR = 3.03 (1.10-8.32), p=0.03}; no difference was found among those with CD4 cell percent >5-14.9% and <5%.

CONCLUSION

Treatment with generic adult FDC for HIV-infected Ugandan children led to sustained clinical, immunologic and virologic response during 96 weeks of ART. Early initiation of ART is key to achieving virological success.

Treatment outcomes among HIV-1 and HIV-2 infected children initiating antiretroviral therapy in a concentrated low prevalence setting in West Africa

Background

There is little data on responses to combination antiretroviral therapy (cART) among HIV-infected children in the West African region. We describe treatment outcomes among HIV-1 and HIV-2 infected children initiating cART in a research clinic in The Gambia, West Africa.

Methods

All treatment naive HIV-infected children who initiated cART according to the WHO ART guidelines for children between October 2004 and December 2009 were included in the analysis. Kaplan-Meir estimates and sign-rank test were used to investigate the responses to treatment.

Results

65 HIV-1 and five HIV-2 infected children aged < 15 years were initiated on cART over this time period. HIV-1 infected children were treated with a combination of Zidovudine or Stavudine + Lamivudine + Nevirapine or Efavirenz while children with HIV-2 were treated with Zidovudine + Lamivudine + ritonavir-boosted Lopinavir. HIV-1 infected children were followed-up for a median (IQR) duration of 20.1 months (6.9 – 34.3), with their median (IQR) age at treatment initiation, CD4% and plasma viral load at baseline found to be 4.9 years (2.1 – 9.1), 13.0% (7.0 – 16.0) and 5.4 log₁₀ copies/ml (4.4 – 6.0) respectively. The median age at treatment initiation of the five HIV-2 infected children was 12 years (range: 4.6 – 14.0) while their median baseline CD4⁺ T cell count and HIV-2 viral load were 140 cells/mm³ (Range: 40 – 570 cells/mm³) and 4.5 log₁₀copies/mL (Range: 3.1 - 4.9 log₁₀copies/mL) respectively.

Among HIV-1 infected children <5 years of age at ART initiation, the median (IQR) increases in CD4% from baseline to 12, 24 and 36 months were 14% (8 – 19; P = 0.0004), 21% (15 – 22; P = 0.005) and 15% (15 – 25; P = 0.0422) respectively, while the median (IQR) increase in absolute CD4 T cell count from baseline to 12, 24 and 36 months for those ≥5 years at ART initiation were 470 cells/mm³ (270 – 650; P = 0.0005), 230 cells/mm³ (30 – 610; P = 0.0196) and 615 cells/mm³ (250 – 1060; P = 0.0180) respectively. The proportions of children achieving undetectable HIV-1 viral load at 6-, 12-, 24- and 36 months of treatment were 24/38 (63.2%), 20/36 (55.6%), 8/22 (36.4%) and 7/12 (58.3%) respectively. The probability of survival among HIV-1 infected children after 12 months on ART was 89.9% (95% CI 78.8 – 95.3). CD4 T cell recovery was sub-optimal in all the HIV-2 infected children and none achieved virologic suppression. Two of the HIV-2 infected children died within 6 months of starting treatment while the remaining three were lost to follow-up.

Conclusions

The beneficial effects of cART among HIV-1 infected children in our setting are sustained in the first 24 months of treatment with a significant improvement in survival experience up to 36 months; however the outcome was poor in the few HIV-2 infected children initiated on cART.

Young HIV-infected children and their adult caregivers prefer tablets to syrup antiretroviral medications in Africa

Background

Provision of anti-retroviral therapy (ART) for HIV-infected children is complicated using syrup formulations, which are costlier than tablets, harder to transport and store and difficult for health-workers to prescribe and caregivers to administer. Dispersible/crushable tablets may be more appropriate. We studied the acceptability of syrups and scored tablets among young children who used both in the AntiRetroviral Research fOr Watoto (ARROW) trial.

Methods

ARROW is an ongoing randomized trial of paediatric ART monitoring and treatment strategies in 1206 children in Uganda and Zimbabwe. 405 children initially received syrups of combination ART including Nevirapine, Zidovudine, Abacavir and Lamivudine before changing, when reaching the 12-<15 kg weightband, to scored adult-dose tablets prescribed according to WHO weightband tables. Caregiver expectations and experiences were collected in questionnaires at their last visit on syrups and after 8 and 24 weeks on tablets.

Results

Questionnaires were completed by caregivers of 267 children (median age 2.9 years (IQR 2.5, 3.4)). At last visit on syrups, 79% caregivers reported problems with syrups, mostly related to number, weight, transportation and conspicuousness of bottles. Difficulties taking tablets were expected by 127(48%) caregivers; however, after 8 and 24 weeks, only 26% and 18% reported their children had problems with tablets and no problems were reported with transportation/conspicuousness. Taste, swallowing or vomiting were reported as problems ‘sometimes/often’ for 14%, 9%, 22% children on syrups and 16%, 9%, 8% on tablets. At last visit on syrups, 74% caregivers expected to prefer tablets but only 27% thought their child would. After 8/24 weeks, 94%/97% caregivers preferred tablets and 57%/59% reported their child did.

Conclusions

Most children at about 3 years can take tablets; caregivers and children themselves generally prefer tablets to liquid formulations of HIV medications above this age. Preferences of caregivers and children should be considered when designing and licensing paediatric drug formulations.

Pharmacokinetics and safety of a new paediatric fixed-dose combination of zidovudine/lamivudine/nevirapine in HIV-infected children

BACKGROUND

Alternatives to the available stavudine-containing paediatric fixed-dose combination (FDC) tablets are rapidly needed due to concerns regarding the cumulative toxicity of long-term stavudine exposure. We report the bioavailability and short-term safety of a novel paediatric FDC tablet of zidovudine (ZDV)/lamivudine (3TC)/nevirapine (NVP; 30/15/28 mg) in HIV-infected children.

METHODS

In this Phase I/II open-label pharmacokinetic study, 42 children weighing 6-30 kg treated with NVP-based HAART for ≥4 weeks were randomized to receive the FDC tablets (GPO-VIR Z30) or the liquid formulations. Dosing was weight-based. Intensive 12-h blood sampling was performed after 2 weeks; subjects then crossed-over to the alternate formulation at equal doses and sampling repeated 2 weeks later. Pharmacokinetic parameters were determined by non-compartmental analysis. Buccal-swab samples were collected for cytochrome P450 (CYP)2B6 polymorphism analysis.

RESULTS

With the FDC tablet, the geometric mean (90% CI) area under the curve (AUC) for ZDV, 3TC and NVP was 1.58 (1.49-1.68), 7.78 (7.38-8.19) and 68.88 (62.13-76.36) μg•h/ml, respectively. Rules for NVP therapeutic inadequacy were defined a priori, and despite lower NVP exposure with the tablet (P<0.001), the levels remained therapeutically adequate. ZDV AUC was similar between formulations. 3TC exposure was significantly higher with the tablet but comparable to historical data in adults and children taking branded tablets. While receiving the tablet, NVP AUC in children with CYP2B 516 GG (45%), GT (45%) and TT (10%) genotypes were 67.0, 74.5 and 106.4 μg•h/ml, respectively (P=0.04).

CONCLUSIONS

Disparities in drug exposure between formulations were observed; however, the FDC tablet delivered therapeutically adequate exposures of each drug and could well play an important role in simplifying antiretroviral treatment for children.

Factors influencing plasma nevirapine levels: a study in HIV-infected children on generic antiretroviral treatment in India

BACKGROUND

Nevirapine is an important component of paediatric combination HIV therapy. Adequate drug exposure is necessary in order to achieve long-lasting viral suppression.

OBJECTIVES

To study the influence of age, drug dose and formulation type, nutritional status and CYP2B6 516G>T polymorphism on blood concentrations of nevirapine in children treated with generic antiretroviral drugs.

METHODS

A multicentre study was conducted at four sites in India. HIV-infected children receiving generic nevirapine-based fixed-dose combinations were recruited. Trough and 2 h nevirapine plasma concentrations were determined by HPLC. Characterization of the CYP2B6 gene polymorphism was performed using direct sequencing. Clinical and nutritional status was recorded. Groups were compared using the Mann-Whitney U-test and multivariable logistic regression analysis was performed to identify factors contributing to low drug levels.

RESULTS

Ninety-four children of median age 78 months were studied; 60% were undernourished or stunted. Stunted children had a significantly lower 2 h nevirapine concentration compared with non-stunted children (P < 0.05); there were no significant differences in trough concentrations between different nutritional groups. Nevirapine levels were significantly higher in children with TT compared with GG and GT CYP2B6 genotypes (P < 0.01). Children ≤ 3 years had a 3.2 (95% confidence interval 1.07-9.45) times higher risk of having sub-therapeutic nevirapine concentrations.

CONCLUSIONS

Nevirapine blood concentrations are affected by many factors, most notably age ≤ 3 years; a combination of young age, stunting and CYP2B6 GG or GT genotype could potentially result in sub-therapeutic nevirapine concentrations. Dosing recommendations for children should be reviewed in the light of these findings.

Long-term survival of HIV-infected children receiving antiretroviral therapy in Thailand: a 5-year observational cohort study

BACKGROUND

There are scarce data on the long-term survival of human immunodeficiency virus (HIV)-infected children receiving antiretroviral therapy (ART) in lower-middle income countries beyond 2 years of follow-up.

METHODS

Previously untreated children who initiated ART on meeting immunological and/or clinical criteria were followed in a prospective cohort in Thailand. The probability of survival up to 5 years from initiation was estimated using Kaplan-Meier methods, and factors associated with mortality were assessed using Cox regression analyses.

RESULTS

Five hundred seventy-eight children received ART; of these, 111 (19.2%) were followed since birth. At start of ART (baseline), the median age was 6.7 years, 128 children (22%) were aged <2 years, and the median CD4 cell percentage was 7%. Median duration of follow-up was 53 months; 42 children (7%) died, and 38 (7%) were lost to follow-up. Age <12 months, low CD4 cell percentage, and low weight-for-height z score at ART initiation were independently associated with mortality (P < .001). The probability of survival among infants aged <12 months at baseline was 84.3% at 1 year and 76.7% at 5 years of ART, compared with 95.7% and 94.8%, respectively, among children aged ≥1 year. Low CD4 cell percentage and wasting at baseline had a strong association with mortality among older children but weak or no association among infants.

CONCLUSIONS

Children who initiated ART as infants after meeting immunological and/or clinical criteria had a high risk of mortality which persisted beyond the first year of therapy. Among older children, those with severe wasting or low CD4 cell percentage at treatment initiation were at high risk of mortality during the first 6 months of therapy. These findings support the scale-up of early HIV diagnosis and immediate treatment in infants, before advanced disease progression in older children.

A chewable pediatric fixed-dose combination tablet of stavudine, lamivudine, and nevirapine: pharmacokinetics and safety compared with the individual liquid formulations in human immunodeficiency virus-infected children in Thailand

BACKGROUND

Pediatric fixed-dose combinations (FDCs) are needed to facilitate antiretroviral therapy in children. We evaluated the relative bioavailability, safety, and therapeutic adequacy of a novel chewable pediatric FDC tablet of stavudine (7 mg), lamivudine (30 mg), and nevirapine (50 mg), referred to as GPO-VIR S7, and compared it with the individual original brand-name liquid formulations in human immunodeficiency virus-infected Thai children.

METHODS

The International Maternal Pediatric Adolescent AIDS Clinical Trials group (IMPAACT) P1056 study was a phase I/II, 2-arm, randomized, open-label, multidose pharmacokinetic cross-over study. Children ≥6 to ≤30 kg receiving nevirapine-based HAART for at least 4 weeks were randomized to receive GPO-VIR S7 chewable tablets or the equivalent liquid formulations. Children were stratified by weight and dosing was weight-based. Intensive 12-hour blood sampling was performed on day 28, and subjects then crossed-over to the alternate formulation at equal doses with identical 12-hour sampling on day 56. Pharmacokinetic indices were determined by noncompartmental analysis.

RESULTS

Thirty-four children completed the study. While taking Government Pharmaceutical Organization (GPO)-VIR S7 the geometric mean (90% CI) area under the curve was 1.54 μg·hr/mL (1.42-1.67) for stavudine, 6.39 (5.82-7.00) for lamivudine, and 74.06 (65.62-83.60) for nevirapine. Nevirapine drug exposure for GPO-VIR S7 was therapeutically adequate. Geometric mean area under the curve ratios (90% CI) of GPO-VIR S7/liquid formulation for stavudine, lamivudine, and nevirapine were 0.97 (0.92-1.02), 1.41 (1.30-1.53), and 1.08 (1.04-1.13), respectively. No serious drug-related toxicity was reported.

CONCLUSIONS

The chewable FDC was safe and provided therapeutically adequate plasma drug exposures in human immunodeficiency virus-infected children. Substituting the FDC for liquid formulations can simplify antiretroviral therapy.

Discontinuation of standard first-line antiretroviral therapy in a cohort of 1434 Malawian children

The standard first-line antiretroviral (ART) regimen in Malawi for both adults and children is a fixed-dose combination tablet containing stavudine (d4T), lamivudine (3TC) and nevirapine (NVP). This regimen has been shown to yield satisfactory virologic and immunologic outcomes in children. Published studies have described insights into discontinuation of first-line regimen and toxicities of ART in adults, but similar studies in paediatric populations are lacking.

A retrospective cohort study was undertaken to assess reasons for discontinuation of the standard first-line ART regimen (d4T/3TC/NVP) in a paediatric population. In total, 1434 patients met eligibility criteria and were included. The cohort had mean and median age at ART initiation of 4.7 years and 2.9 years, respectively (range: 0.1 months-18.7 years). The gender distribution was 47% female and 53% male. Median follow-up time on ART was 1.8 years (range: 2 weeks-3.9 years). A majority (96.2%) of patients were on the standard first-line ART regimen, while 3.8% (54) were on a different regimen. Twenty-eight patients (2.0%) were on an alternative first-line regimen due to toxicities, 22 patients (1.5%) were on a second-line regimen due to ART failure, and four patients (0.3%) were on a non-standard regimen for other clinical reasons.

Of the 28 patients who experienced toxicities requiring ART regimen change, 60.7% (17) were caused by NVP, 39.3% (11) by d4T, and none by 3TC. The median time from first-line ART initiation to alternative first-line ART was two months (range: 10 days-28.1 months); 60.7% of patients on alternative first-line ART were male. Average time on ART until switch to second-line ART regimen was 16.3 months (SD: 9.3 months). The probability of failure after one year on first-line regimen was 1.6% (95% CI: 0.9-2.6).

There was no compelling evidence in this cohort, representing approximately 10% of all children on ART in Malawi, to support changing the standard paediatric first-line regimen based on early toxicities or failure. However, experience from the national adult cohort, longer term follow up of the paediatric cohort in this study, emerging data on resistance after single-dose NVP containing mother to child transmission antiretroviral prophylaxis, and new 2009 World Health Organization ART recommendations may influence national policy change to a different first-line regimen.

Pharmacokinetics of generic and trade formulations of lamivudine, stavudine and nevirapine in HIV-infected Malawian children

BACKGROUND

The aim of this study was to evaluate the pharmacokinetics of lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in HIV-infected Malawian children receiving quartered tablet multiples of Triomune 40 (generic tablet [GT]) compared with individual generic liquid (GL) and trade liquid (TL).

METHODS

This was a prospective randomized three-way crossover study. Patients (8-<12 kg, 18-<22 kg or 28-<32 kg body weight) taking Triomune 40 were recruited and randomized to receive GT twice daily (one-quarter, one-half or three-quarter tablets using Malawi treatment guidelines), GL twice daily (in the equivalent dose of GT) or TL twice daily (dosed using weight and age from US Department of Health and Human Services paediatric treatment guidelines). After 10 days of one formulation, 6-h pharmacokinetic sampling was performed, and patients were crossed over to subsequent formulations. Baseline concentration (C(0 h)), area under the curve (AUC)(0-6 h), maximum plasma concentration (C(max)) and time to C(max) were generated for each antiretroviral treatment.

RESULTS

A total of 7 males and 11 females (6 in each GT dosing group) with a median (range) age of 7.2 years (1.3-13.6), weight of 19 kg (9.0-30.5) and height of 109 cm (75-132) were recruited. Combining all patients, no difference in pharmacokinetics was noted among the formulations for all drugs. However, patients in the one-quarter GT dosing group (8-<12 kg) had lower 3TC exposures than with the GL or TL (3TC AUC(0-6 h) 1,102, 1,720 and 2,060 h*ng/ml, respectively; P<0.005) and had more subtherapeutic NVP C(0 h) (10 of 13 occasions versus the one-half and three-quarter tablet groups). Compared with Western paediatric cohorts, Malawians had concentrations 30-40% lower for 3TC and d4T and 50% higher for NVP.

CONCLUSIONS

Quartered multiples of Triomune 40 are appropriate for children 18-<22 kg and 28-<32 kg in weight; however, alternative formulations are suggested in children weighing 8-<12 kg.

Dose adjustment of the non-nucleoside reverse transcriptase inhibitors during concurrent rifampicin-containing tuberculosis therapy: one size does not fit all

IMPORTANCE OF THE FIELD

HIV/tuberculosis (TB) co-infection is common and associated with high mortality. Simultaneous highly active antiretroviral therapy during TB treatment is associated with substantial survival benefit but drug-drug interactions complicate NNRTI dosing.

AREAS COVERED IN THIS REVIEW

We reviewed the impact of rifampicin-containing TB therapy on the NNRTIs pharmacokinetics and clinical outcome. PubMed database was searched from 1966 to July 2009 using the terms efavirenz, rifampicin, nevirapine, pharmacokinetics, pharmacogenetics, HIV, TB, CYP2B6, CYP3A4 and metabolism. References from identified articles and abstracts from meetings were also reviewed.

WHAT THE READER WILL GAIN

A comprehensive review of the literature on this subject including pharmacokinetic and clinical studies. Most studies were small, observational or underpowered to detect the true effect of rifampicin on NNRTI-based therapy. None of the studies were controlled for genetic factors and there were limited data on children.

TAKE HOME MESSAGE

There were insufficient data to make definitive recommendations about dose adjustment of the NNRTIs during rifampin-containing therapy. Current data suggest that the standard dose of efavirenz or nevirapine is adequate in most HIV/TB co-infected adults. However, more research is needed in pediatric populations as well as to define role of drug-gene interactions.

Steady-state nevirapine, lamivudine and stavudine levels in Malawian HIV-infected children on antiretroviral therapy using split Triomune 30 tablets

BACKGROUND

Children remain under-represented in national antiretroviral treatment (ART) programmes in settings with limited resources and high HIV prevalence. In Malawi, an increasing number of HIV-infected children have been started on ART with split tablets of an adult fixed-dose combination drug in the past few years. In 2006, the national paediatric ART regime was changed from Triomune 40 (T40) to Triomune 30 (T30).

METHODS

This was a cross-sectional study conducted at the paediatric ART clinic in Blantyre (Malawi) from September 2006 to July 2007. Children taking T30 for > 6 weeks from each dosing weight band (<5, 5-<8, 8-<12, 12-<14, 14-<19, 19-<26, 26-<30 and > or = 30 kg) were recruited. Plasma drug concentration, CD4+ T-cell count and HIV viral load were measured.

RESULTS

A total of 74 children were analysed. The median nevirapine (NVP) concentration was 7.35 mg/l. A therapeutic NVP plasma level > 3 mg/l was found in 62 (87.8%) children. A subtherapeutic NVP level (< 3 mg/l) occurred significantly more often in children treated with T30 doses between one-quarter tablet once daily and one-half tablet twice daily (P=0.035). Median prescribed NVP dose was 342 mg/m(2)/day, but 13 (17.6%) children received a dose below the recommended dose of 300 mg/m(2)/day. Compared with a historical control, the median prescribed NVP dose was increased (from 243 to 342 mg/m(2)/day).

CONCLUSIONS

Our findings indicate that with the Malawian T30-based ART regime, the majority (87.8%) of children in the study group achieved a therapeutic NVP level. However, treatment remains suboptimal especially for young children receiving T30 dosages less than or equal to one-half tablets twice daily and child appropriate formulations are warranted.

Therapeutic drug monitoring of lopinavir in human immunodeficiency virus-infected children receiving adult tablets

Because of the lack of a lopinavir/ritonavir (LPV/r) pediatric formulation, 54 HIV-infected children were given generic LPV/r adult tablets. Of 54 children, 21 took cut pills to get the appropriate dose. The median (interquartile range) LPV trough serum concentration (C trough) was 6.7 (5.0-9.9) mg/L. All the children had C trough >1.0 mg/L and 96% had values >4.0 mg/L. LPV/r adult tablets can be used in children when it is necessary.

Pharmacokinetics of nevirapine in HIV-infected children with and without malnutrition receiving divided adult fixed-dose combination tablets

OBJECTIVES

To determine the relationship between nutritional status and nevirapine exposure by comparing the pharmacokinetics of nevirapine in HIV-infected children of different ages with and without malnutrition receiving divided tablets of Triomune 30 (stavudine + lamivudine + nevirapine) in accordance with Malawi National Guidelines.

METHODS

Children were recruited in weight-based dosage bands and nutritional status classified according to weight for height. Total and unbound plasma nevirapine concentrations were measured over a full dosing interval. Multivariate linear and logistic regression analyses were performed to determine the effects of malnutrition, age, dose and other factors on nevirapine exposure and likelihood of achieving therapeutic nevirapine trough concentrations.

RESULTS

Forty-three children were recruited (37 included for analysis). Mild to moderate malnutrition was present in 12 (32%) children; 25 (68%) were of normal nutritional status. There was no effect of malnutrition on any measure of total drug exposure or on the unbound fraction of nevirapine. Nevirapine exposure was strongly related to dose administered (P = 0.039) and to age (for every yearly increase in age there was an approximately 88% increase in the odds of achieving a therapeutic nevirapine concentration; P = 0.056, 95% confidence interval 0.983-3.585).

CONCLUSIONS

Use of divided adult Triomune 30 tablets in treating young children results in significant underdosing. No independent effect of malnutrition on total and unbound nevirapine exposures was observed. These data support the use of bespoke paediatric antiretroviral formulations.

Pediatric HIV: new opportunities to treat children

BACKGROUND

Treating HIV-infected children remains a challenge due to a lack of treatment options, appropriate drug formulations and, in countries with limited resources, insufficient access to diagnostic tests and treatment.

OBJECTIVE

To summarize current data concerning new opportunities to improve the treatment of HIV-infected children.

METHODS

This review includes data from the most recently published peer-reviewed publications, guidelines or presentations at international meetings concerning new ways to treat HIV-infected children.

RESULTS/CONCLUSIONS

New WHO guidelines recommend starting combination antiretroviral treatment in all infants aged < 1 year. Although this is common practice in some high-income countries, implementation of these recommendations in countries with limited resources is still a challenge. There is still an important gap between the availability of licensed drugs in children compared with adults. There remains a need for further pharmacokinetic studies, and for more pediatric formulations of antiretroviral drugs with improved palatability.

Predictors of virologic failure and genotypic resistance mutation patterns in thai children receiving non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy

BACKGROUND

Nonnucleoside reverse transcription inhibitor (NNRTI)-based antiretroviral therapy (ART) has been widely used as a first-line regimen for the treatment of HIV. This study aimed to determine the rate and predictors of virologic failure and describe patterns of resistance mutation.

METHODS

The inclusion criteria were children who were <18 years and receiving NNRTI-based ART. Plasma HIV-1 RNA and CD4 were monitored every 6 months. Virologic failure was defined as plasma HIVRNA >1000 copies/mL.

RESULTS

Forty (20%) of 202 children had virologic failure, of whom 33 (16%) failed in the first year of therapy. By multivariate analysis, the children who received nevirapine were 3.7 times more likely to develop virologic failure than those receiving efavirenz (P = 0.006). The prevalence's of patients with >or=1 major mutations conferring drug resistance to nucleoside reverse transcription inhibitors (NRTIs) and NNRTIs were 89% and 97%, respectively. The common NNRTI mutations were Y181C/I (58%) and K103N (34%). The NRTI mutations were M184V/I (84%), K65R (11%), Q151M (5%), and >or=3 TAMs (3%).

CONCLUSIONS

The virologic failure rate in children was high and mostly occurred in the first year of treatment. The most common resistance mutations were those conferring resistance to NNRTIs and lamivudine. There were few instances of multiNRTI resistance. Early detection of virologic failure might allow more options for second-line regimens.

Routine offering of HIV testing to hospitalized pediatric patients at university teaching hospital, Lusaka, Zambia: acceptability and feasibility

OBJECTIVES

The difficulties diagnosing infants and children with HIV infection have been cited as barriers to increasing the number of children receiving antiretroviral therapy worldwide.

DESIGN

We implemented routine HIV antibody counseling and testing for pediatric patients hospitalized at the University Teaching Hospital, a national reference center, in Lusaka, Zambia. We also introduced HIV DNA polymerase chain reaction (PCR) testing for early infant diagnosis.

METHODS

Caregivers/parents of children admitted to the hospital wards were routinely offered HIV counseling and testing for their children. HIV antibody positive (HIV+) children <18 months of age were tested with PCR for HIV DNA.

RESULTS

From January 1, 2006, to June 30, 2007, among 15,670 children with unknown HIV status, 13,239 (84.5%) received counseling and 11,571 (87.4%) of those counseled were tested. Overall, 3373 (29.2%) of those tested were seropositive. Seropositivity was associated with younger age: 69.6% of those testing HIV antibody positive were <18 months of age. The proportion of counseled children who were tested increased each quarter from 76.0% in January to March 2006 to 88.2% in April to June 2007 (P < 0.001). From April 2006 to June 2007, 1276 PCR tests were done; 806 (63.2%) were positive. The rate of PCR positivity increased with age from 22% in children <6 weeks of age to 61% at 3-6 months and to 85% at 12-18 months (P < 0.001).

CONCLUSIONS

Routine counseling and antibody testing of pediatric inpatients can identify large numbers of HIV-seropositive children in high prevalence settings. The high rate of HIV infection in hospitalized infants and young children also underscores the urgent need for early infant diagnostic capacity in high prevalence settings.

Success with antiretroviral treatment for children in Kigali, Rwanda: experience with health center/nurse-based care

BACKGROUND

Although a number of studies have shown good results in treating children with antiretroviral drugs (ARVs) in hospital settings, there is limited published information on results in pediatric programs that are nurse-centered and based in health centers, in particular on the psychosocial aspects of care.

METHODS

Program treatment and outcome data were reported from two government-run health centers that were supported by Médecins Sans Frontières (MSF) in Kigali, Rwanda between October 2003 and June 2007. Interviews were held with health center staff and MSF program records were reviewed to describe the organization of the program. Important aspects included adequate training and supervision of nurses to manage ARV treatment. The program also emphasized family-centered care addressing the psychosocial needs of both caregivers and children to encourage early diagnosis, good adherence and follow-up.

RESULTS

A total of 315 children (< 15 years) were started on ARVs, at a median age of 7.2 years (range: 0.7-14.9). Sixty percent were in WHO clinical stage I/II, with a median CD4% of 14%. Eighty-nine percent (n = 281) started a stavudine-containing regimen, mainly using the adult fixed-dose combination. The median follow-up time after ARV initiation was 2 years (interquartile range 1.2-2.6). Eighty-four percent (n = 265) of children were still on treatment in the program. Thirty (9.5%) were transferred out, eight (2.6%) died and 12 (3.8%) were lost to follow-up. An important feature of the study was that viral loads were done at a median time period of 18 months after starting ARVs and were available for 87% of the children. Of the 174 samples, VL was < 400 copies/ml in 82.8% (n = 144). Two children were started on second-line ARVs. Treatment was changed due to toxicity for 26 children (8.3%), mainly related to nevirapine.

CONCLUSION

This report suggests that providing ARVs to children in a health center/nurse-based program is both feasible and very effective. Adequate numbers and training of nursing staff and an emphasis on the psychosocial needs of caregivers and children have been key elements for the successful scaling-up of ARVs at this level of the health system.

Global challenges in the development and delivery of paediatric antiretrovirals

By the end of 2006, compared with 28% coverage for adults, only 15% of children with HIV that needed antiretroviral treatment were receiving it. Major challenges in delivering treatment include the lack of paediatric antiretrovirals that can be dosed in small children and limited studies examining safety and efficacy for existing antiretroviral formulations. The high costs of treatment have been reduced through the use of generic, fixed-dose combination drugs. Evidence-based strategies for managing resistance and the scale-up of pharmacological trials for children in low- and middle-income countries are crucial to the success and future development of paediatric antiretrovirals.

Nevirapine, stavudine and lamivudine pharmacokinetics in African children on paediatric fixed-dose combination tablets

OBJECTIVE

Triomune Baby and Junior have been developed in response to the urgent need for appropriate paediatric fixed-dose combination antiretroviral tablets, with higher nevirapine to stavudine and lamivudine ratios than adult tablets, in accordance with paediatric recommendations. We determined whether this ratio results in optimal exposure in the target population.

METHODS

Seventy-one Zambian children were treated with Triomune Baby or Junior dosed according to weight bands. After 4 weeks or more, a 12-h pharmacokinetic curve was recorded. Antiretroviral plasma concentrations were assayed by high-performance liquid chromatography.

RESULTS

Six children were excluded because of poor adherence. Of the remaining 65, 24 (37%) were female, 24 (37%) weighed less than 15 kg and most were malnourished. Mean (range) nevirapine C12h, Cmax and AUC12h of 6.0 (1.4, 16.9) mg/l, 10.0 (3.8, 22.5) mg/l and 94.4 (32.1, 232) mg/l per hour were higher than those reported in adults. Nevirapine C12h was subtherapeutic (< 3.0 mg/l) in four children (6%). Mean stavudine and lamivudine C12h, Cmax, AUC12h (< 0.015 mg/l, 0.45 mg/l, 1.05 mg/l per hour and 0.09 mg/l, 1.33 mg/l, 5.42 mg/l per hour) were comparable to adults. There was no evidence of a difference in nevirapine AUC12h across weight bands (P = 0.2), whereas the difference in stavudine (P = 0.0003) and lamivudine AUC12h (P = 0.01) was driven by the single weight band with unequal dosing.

CONCLUSION

Nevirapine concentrations were higher but more variable than in adults; the pharmacokinetic parameters of stavudine and lamivudine were comparable to adults. As nevirapine underdosing is of greater concern than overdosing, the Triomune Baby and Junior ratio appears to be appropriate for children weighing 6 kg and over. Further research is required for children under 6 kg.

Rapid CD4 decline after interruption of non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy in a resource-limited setting

Background

Non-nucleoside reverse transcriptase inhibitor (NNRTI) with stavudine and lamivudine is widely used as the first-line antiretroviral therapy (ART) in resource-limited settings. Lipodystrophy is common and options for switching ART regimen are limited; this situation can lead to patients' poor adherence and antiretroviral resistance. Treatment interruption (TI) in patients with high CD4 cell counts, lipodystrophy, and limited options may be an alternative in resource-limited settings. This study aimed to determine time to resume ART after TI and predictors for early resumption of ART in a resource-limited setting.

Methods

A prospective study was conducted in January 2005 to December 2006 and enrolled HIV-infected patients with HIV-1 RNA <50 copies/mL, CD4 > 350 cells/mm³, and willing to interrupt ART. CD4 cell count, HIV-1 RNA, lipid profile, and lipodystrophy were assessed at baseline and every 3 months. ART was resumed when CD4 declined to <250 cells/mm³ or developed HIV-related symptoms. Patients were grouped based on ART regimens [NNRTI or protease inhibitor (PI)] prior to TI.

Results

There were 99 patients, 85 in NNRTI group and 14 in PI group. Mean age was 40.6 years; 46% were males. Median duration of ART was 47 months. Median nadir CD4 and baseline CD4 were 151 and 535 cells/mm³, respectively. Median CD4 change at 3 months after TI were -259 (NNRTI) and -105 (PI) cells/mm³ (p = 0.038). At 13-month median follow-up, there was no AIDS-defining illness; 38% (NNRTI) and 29% (PI) of patients developed HIV-related symptoms. ART was resumed in 51% (NNRTI) and 36% (PI) of patients (p = 0.022). By Kaplan-Meier analysis, median time to resume ART was 5.5 (NNRTI) and 14.2 (PI) months (log rank test, p = 0.026). By Cox's regression analysis, NNRTI-based ART (HR 4.9; 95%CI, 1.5–16.3), nadir CD4 <100 cells/mm³ (HR 2.7; 95%CI 1.4–5.3) and baseline CD4 <500 cells/mm³ (HR 1.6; 95%CI, 1.2–3.1) were predictors for early ART resumption.

Conclusion

TI of NNRTI-based ART leads to rapid CD4 decline and high probability of early ART resumption and should be avoided. It is necessary to scale-up the options for HIV-infected patients with lipodystrophy in resource-limited settings.

Effectiveness of highly active antiretroviral therapy in HIV-positive children: evaluation at 12 months in a routine program in Cambodia

OBJECTIVE

Increasing access to highly active antiretroviral therapy to reach all those in need in developing countries (scale up) is slowly expanding to HIV-positive children, but documented experience remains limited. We aimed to describe the clinical, immunologic, and virologic outcomes of pediatric patients with >12 months of highly active antiretroviral therapy in 2 routine programs in Cambodia.

METHODS

Between June 2003 and March 2005, 212 children who were younger than 13 years started highly active antiretroviral therapy. Most patients started a standard first-line regimen of lamivudine, stavudine, and nevirapine, using split adult fixed-dosage combinations. CD4 percentage and body weight were monitored routinely. A cross-sectional virologic analysis was conducted in January 2006; genotype resistance testing was performed for patients with a detectable viral load.

RESULTS

Mean age of the subjects was 6 years. Median CD4 percentage at baseline was 6. Survival was 92% at 12 months and 91% at 24 months; 13 patients died, and 4 were lost to follow-up. A total of 81% of all patients had an undetectable viral load. Among the patients with a detectable viral load, most mutations were associated with resistance to lamivudine and non-nucleoside reverse-transcriptase inhibitor drugs. Five patients had developed extensive antiretroviral resistance. Being an orphan was found to be a predictor of virologic failure.

CONCLUSIONS

This study provides additional evidence of the effectiveness of integrating HIV/AIDS care with highly active antiretroviral therapy for children in a routine setting, with good virologic suppression and immunologic recovery achieved by using split adult fixed-dosage combinations. Viral load monitoring and HIV genotyping are valuable tools for the clinical follow-up of the patients. Orphans should receive careful follow-up and extra support.

Risk factors for early mortality in children on adult fixed-dose combination antiretroviral treatment in a central hospital in Malawi

OBJECTIVES

In children aged less than 15 years, to determine the cumulative proportion of deaths occurring within 3 and 6 months of starting split-tablet adult fixed-dose combination antiretroviral therapy (ART) and to identify risk factors associated with early deaths.

DESIGN

A retrospective cohort analysis.

METHODS

Data were collected and analysed from ART patient master cards and the ART register of all children registered for treatment between July 2004 and September 2006 in the ART clinic at Mzuzu Central Hospital, northern Malawi.

RESULTS

A total of 439 children started on ART, of whom 220 (50%) were male; 37 (8%) were aged less than 18 months, 172 (39%) 18 months to 5 years, and 230 (52%) were 6-14 years. By September 2006, 49 children (11%) had died, of whom 35 (71%) died by 3 months and 44 (89%) by 6 months. The cumulative incidence of death at 3, 6, 12 and 24 months after ART was 8, 12, 13 and 15%, respectively. After multivariate analysis, being in World Health Organization clinical stage 4, having severe wasting and severe immunodeficiency were factors significantly associated with 3-month mortality and 6-month mortality, respectively.

CONCLUSION

Although children do well on ART, there is high early mortality. Scaling up HIV testing and simple diagnostic tests for infants and children, expanding routine provision of cotrimoxazole prophylaxis, and investigating the role of nutritional interventions are three measures that, if implemented and expanded countrywide, may improve ART outcomes.

Nevirapine concentration in nonstimulated saliva: an alternative to plasma sampling in children with human immunodeficiency virus infection

BACKGROUND

The monitoring of nevirapine (NVP) concentrations in pediatric patients has gained interest since the introduction of NVP as part of the preferred first-line antiretroviral regimen for human immunodeficiency virus (HIV)-infected children in resource-limited settings. Adequate trough concentrations of NVP predict successful therapy, whereas subtherapeutic levels are correlated with virologic failure and development of resistance. The aim of this study was to determine the extent of agreement between total and free plasma NVP concentrations and nonstimulated saliva NVP concentrations and to evaluate the feasibility of saliva sampling as an alternative tool for therapeutic drug monitoring of NVP in children.

DESIGN AND METHODS

The study was designed as an observational cohort analysis. NVP concentrations were obtained in paired plasma and saliva samples of pediatric patients receiving antiretroviral therapy, including NVP. NVP plasma and saliva concentrations were determined by a tandem-mass spectrometric method. The intraclass correlation coefficient and Bland-Altman analysis were used to evaluate agreement and to assess pattern in any discrepancies between measurements.

RESULTS

For the random paired plasma and saliva NVP sampling, 19 African-American children (8 boys, 11 girls) with a median age of 8.0 years were enrolled. Two male subjects were recruited for the 12 hour NVP plasma and saliva pharmacokinetics study. The intraclass correlations between saliva and serum measurements of NVP concentrations indicated >90% agreement between these two modes of measurement. The saliva concentrations reflected the free concentrations very closely but were on average 34% higher. The Bland-Altman plots indicated that the discrepancy between saliva and plasma measures is consistent across the range of average NVP concentrations.

CONCLUSIONS

Our study results strongly indicate agreement between saliva and plasma NVP concentrations in pediatric patients with HIV infection, on the basis of Bland-Altman analysis. Nonstimulated NVP saliva concentrations can be used as an alternative noninvasive, reliable, cost-effective method for direct measurement of adherence and application of therapeutic drug monitoring in NVP therapy.

International perspectives, progress, and future challenges of paediatric HIV infection

Paediatric HIV infection is a growing health challenge worldwide, with an estimated 1500 new infections every day. In developed countries, well established prevention programmes keep mother-to-child transmission rates at less than 2%. However, in developing countries, where transmission rates are 25-40%, interventions are available to only 5-10% of women. Children with untreated natural infection progress rapidly to disease, especially in resource-poor settings where mortality is greater than 50% by 2 years of age. As in adult infection, antiretroviral therapy has the potential to rewrite the natural history of HIV, but is accessible only to a small number of children needing therapy. We focus on the clinical and immunological features of HIV that are specific to paediatric infection, and the formidable challenges ahead to ensure that all children worldwide have access to interventions that have proved successful in developed countries.

Antiretroviral therapy for children in the routine setting in Malawi

Malawi is scaling up antiretroviral therapy (ART) for HIV-infected patients. Using a fixed-dose combination of stavudine+lamivudine+nevirapine ('Triomune') as the first-line regimen, split tablets are given to children with doses according to body weight. By March 2006, a total of 46 702 patients had been started on ART, of whom 2718 (5.8%) were children aged <15 years. In a subset of 935 children, comprising 486 boys and 449 girls, 1.5% were aged <1 year, 26% were aged 1-4 years, 39% were aged 5-9 years and 33% were aged 10-14 years. Between July and September 2005, 7905 patients started ART, comprising 7469 adults and 436 children. Six-month cohort outcomes censored on 31 March 2006 showed significantly more children alive and significantly fewer children dead or defaulted compared with adults. Between January and March 2005, 4580 patients started ART, comprising 4347 adults and 233 children. Twelve-month cohort outcomes censored on 31 March 2006 showed significantly more children alive compared with adults. The results of this national study should encourage other programmes to invest in ART for children and particularly to monitor their treatment outcomes.

Increasing antiretroviral drug access for children with HIV infection

Although there have been great gains in the prevention of pediatric HIV infection and provision of antiretroviral therapy for children with HIV infection in resource-rich countries, many barriers remain to scaling up HIV prevention and treatment for children in resource-limited areas of the world. Appropriate testing technologies need to be made more widely available to identify HIV infection in infants. Training of practitioners in the skills required to care for children with HIV infection is required to increase the number of children receiving antiretroviral therapy. Lack of availability of appropriate antiretroviral drug formulations that are easily usable and inexpensive is a major impediment to optimal care for children with HIV. The time and energy spent trying to develop liquid antiretroviral formulations might be better used in the manufacture of smaller pill sizes or crushable tablets, which are easier to dispense, transport, store, and administer to children.

Plasma nevirapine levels, adverse events and efficacy of antiretroviral therapy among HIV-infected patients concurrently receiving nevirapine-based antiretroviral therapy and fluconazole

Background

The clinical data of plasma NVP level, safety and efficacy of antiretroviral therapy (ART) for the concurrent use of nevirapine (NVP)-based ART and fluconazole (FLU) is scanty.

Methods

A retrospective study was conducted in patients who were initiated NVP-based ART between October 2004 and November 2005. The objectives were to compare NVP levels, adverse events, and 36-week efficacy of NVP-based ART between patients who did not receive FLU (group A) and those who received FLU 200 mg/day or 400 mg/day (group B).

Results

There were 122 patients with mean ± SD age of 36 ± 9 years; 81 in group A and 41 in group B. Median (IQR) baseline CD4 cell count was 29 (8–79) cell/mm³ in group A and 19 (8–33) cell/mm³ in group B (P = 0.102). Baseline characteristics between the two groups were similar. Mean ± SD NVP levels were 6.5 ± 3.0 mg/L in group A and 11.4 ± 6.1 mg/L in group B(P < 0.001). One (2.4%) patient in group B developed clinical hepatitis (P = 0.336). Six (7.4%) patients in group A developed NVP-related skin rashes (P = 0.096). There were no differences in term of 36-week antiviral efficacy between the two groups (P > 0.05).

Conclusion

Co-administration of NVP and daily dosage of FLU (200 mg/day and 400 mg/day) results in markedly increased trough plasma NVP level when compared to the administration of NVP alone. The concurrent use of NVP and FLU in very advanced HIV-infected patients is well-tolerated. The immunological and virological responses are favorable.

Nevirapine Concentrations in HIV-Infected Children treated with Divided Fixed-Dose Combination Antiretroviral Tablets in Malawi and Zambia

Objective

To investigate nevirapine concentrations in African HIV-infected children receiving divided Triomune tablets (stavudine+lamivudine+nevirapine).

Design

Cross-sectional study.

Methods

Steady-state plasma nevirapine concentrations were determined in Malawian and Zambian children aged 8 months to 18 years receiving Triomune in routine outpatient settings. Predictors from height-for-age, body mass index (BMI)-for-age, age, sex, post-dose sampling time and dose/m2/day were investigated using centre-stratified regression with backwards elimination ( P<0.1).

Results

Of the 71 Malawian and 56 Zambian children (median age 8.4 vs 8.5 years, height-for-age -3.15 vs -1.84, respectively), only 1 (3%) of those prescribed ≥300 mg/m2/day nevirapine had subtherapeutic concentrations (<3mg/l) compared with 22 (23%) of those prescribed <300 mg/m2/day; most children with subtherapeutic nevirapine concentrations were taking half or quarter Triomune tablets. Lower nevirapine concentrations were independently associated with lower height-for-age (indicating stunting) (0.37 mg/l per unit higher [95% confidence interval (CI): -0.003, +0.74]; P=0.05), lower prescribed dose/m2 (+0.89 mg/l per 50mg/m2 higher [95% CI: 0.32, 1.46]; P=0.002) and higher BMI-for-age (indicating lack of wasting) (-0.42mg/l per unit higher [95% CI: -0.80, -0.04]; P=0.03).

Conclusions

Currently available adult fixed-dose combination tablets are not well suited to children, particularly at younger ages: Triomune 30 is preferable to Triomune 40 because of the higher dose of nevirapine relative to stavudine. Further research is required to confirm that concentrations are reduced in stunted children but increased in wasted children. Development of appropriate paediatric fixed-dose combination tablets is essential if antiretroviral therapy is to be made widely available to children in resource-limited settings.

In resource-limited settings good early outcomes can be achieved in children using adult fixed-dose combination antiretroviral therapy

OBJECTIVES

To (a) determine early treatment outcomes and (b) assess safety in children treated with adult fixed-dose combination (FDC) antiretroviral tablets.

SETTING

Sixteen Medecins Sans Frontieres (MSF) HIV programs in eight countries in resource-limited settings (RLS).

METHODS

Analysis of routine program data gathered June 2001 to March 2005.

RESULTS

A total of 1184 children [median age, 7 years; inter-quartile range (IQR), 4.6-9.3] were treated with antiretroviral therapy (ART) of whom 616(52%) were male. At ART initiation, Centres for Disease Control stages N, A, B and C were 9, 14, 38 and 39%, respectively. Children were followed up for a median period of 6 months (IQR, 2-12 months). At 12 months the median CD4 percentage gain in children aged 18-59 months was 15% (IQR, 6-18%), and the percentage with CD4 gain < 15% was reduced from 85% at baseline to 11%. In those aged 60-156 months, median CD4 cell count gain was 275 cells/microl (IQR, 84-518 cells/microl), and the percentage with CD4 < 200 cells/mul reduced from 51% at baseline to 11%. Treatment outcomes included; 1012 (85%) alive and on ART, 36 (3%) deaths, 15 (1%) stopped ART, 89 (8%) lost to follow-up, and 31 (3%) with unknown outcomes. Overall probability of survival at 12 months was 0.87 (0.84-0.89). Side effects caused a change to alternative antiretroviral drugs in 26 (2%) but no deaths.

CONCLUSIONS

Very satisfactory early outcomes can be achieved in children in RLS using generic adult FDC antiretroviral tablets. These findings strongly favour their use as an "interim solution" for scaling-up ART in children; however, more appropriate pediatric antiretroviral drugs remain urgently needed.