Efficacy and plasma concentrations of indinavir when boosted with ritonavir in human immunodeficiency virus-infected Thai children

Thai national guidelines for the use of antiretroviral therapy in pediatric HIV infection in 2010

With better knowledge and availability of antiretroviral treatments, the Thai National HIV Guidelines Working Group has issued treatment guidelines for children in Thailand in March 2010. The most important aspects of these new guidelines are detailed below. ART should be initiated in infants less than 12 months of age at any CD4 level regardless of symptoms and in all children at CDC clinical stage B and C or WHO clinical stages 3 and 4. For children with no or mild symptoms consider CD4-guided thresholds of CD4 <25% (children aged one to five years) or CD4 <350 cells/mm3 (children 5 years or older). The preferred first-line regimen in children aged < 3 years is AZT+3TC+NVP. For children >3 years of age the preferred regimen is AZT+3TC+EFV. If an infant has previously been exposed to NVP perinatally, use AZT+3TC+LPV/r as empirical first regimen. In adolescents, consider TDF+3TC+EFV. The preferred ARV treatment in children who failed first line regimens of 2NRTI+NNRTI (Salvage treatment) comprises 2NRTI (guided by genotype) +LPV/r, and an alternative regimen is 2NRTI (guided by genotype) +ATV/ r (use in cases with dyslipidemia who are six years or older). In cases with extensive NRTI resistance with no effective NRTI option available, double boosted PI with LPV/r+SQV or LPV/r+IDV can be considered. Consultation with an expert is recommended. Laboratory monitoring is recommended for CD4 and every six months. Viral load at least at 6 and 12 months after initiation or change of regimen, then yearly thereafter. More frequent viral load monitoring is advised for cases with unsuccessful virologic response, infants, children with imperfect adherence, or those using of third line regimens. Toxicity monitoring depends on the drug received, at least every six months, and more often as clinically indicated. These include, but are not limited to, complete blood count, renal function tests, liver function tests, urinanalysis, and lipid profiles. Therapeutic drug monitoring is recommended in cases that have ARV-related toxicity, receiving non-standard dosing or regimens, using double boosted PI, and in those with renal or hepatic impairment.

Children with HIV are not small adults: what is different in pharmacology?

PURPOSE OF REVIEW

The pharmacokinetics of antiretroviral drugs are highly variable among HIV-infected children. This review describes pharmacokinetic processes in children and recent pharmacokinetic data in children with HIV. The general lack of pharmacokinetic data and the potential role of therapeutic drug monitoring are discussed.

RECENT FINDINGS

It was found unexpectedly that exposure to lopinavir is decreased in the first 6 months of life. Recent findings of subtherapeutic efavirenz concentrations in children suggest that pediatric dose recommendations should be re-evaluated. In addition, recommended dosing of lamivudine leads to lower exposure in children younger than 6 years of age. Preliminary results of pediatric fixed-dose combination tablets for HIV-infected children with a higher nevirapine to stavudine and lamivudine ratio than adult fixed-dose combinations suggest adequate drug exposure. As an alternative to plasma sampling, concentrations of nevirapine can be determined in saliva.

SUMMARY

There is a shortage of pharmacokinetic data in the highly variable population of HIV-infected children. Selected pharmacology studies should be undertaken to improve pediatric dose guidance of existing antiretroviral drugs. Therapeutic drug monitoring is a useful tool to optimize treatment in HIV-infected children. More data are needed, however, to establish child-specific reference values.

Pharmacokinetics of darunavir/ritonavir in Asian HIV-1-infected children aged ≥7 years

BACKGROUND

The Asian population, in general, has higher antiretroviral concentrations than those who are not Asian, but there are limited pharmacokinetic data for darunavir/ritonavir in Asian children.

METHODS

Thai children aged ≥7 years and with body weight (BW)≥20 kg who were on darunavir/ritonavir for ≥2 weeks underwent 12-h pharmacokinetics with blood sampling before and at 1, 2, 4, 6, 8, 10 and 12 h post-dosing. Darunavir/ritonavir doses were 375/100 mg twice daily (BW 20 to <30 kg, n=12), 450/100 mg twice daily (BW 30 to <40 kg, n=2) or 600/100 mg twice daily (BW ≥40 kg, n=5). Ritonavir 100 mg soft gel capsules were used instead of solution.

RESULTS

Of the 19 children, 8 were female, median age was 13 years (range 7-16) and median BW was 29.4 kg. The median duration of darunavir/ritonavir treatment was 11 months. The geometric mean values for darunavir were 60.3 h×mg/l for the area under the concentration-time curve at 0-12 h (AUC(0-12)), 8.3 mg/l for the maximum concentration (C(max)) and 3.1 for the concentration prior to the next dose (C(12)) with no differences between dosing groups. All had C(12) above the protein binding adjusted 50% effective concentration (EC(50)) of protease inhibitor-resistant virus (0.55 mg/l). The darunavir pharmacokinetic parameters were similar to those in non-Asian individuals from the DELPHI study, in which 13 of 20 with BW<40 kg used 50 or 60 mg ritonavir boosting.

CONCLUSIONS

Thai children aged ≥7 years who were on standard darunavir dosing with 100 mg ritonavir boosting had adequate and comparable darunavir AUC(0-12), C(max) and C(12) to non-Asian children who mainly used lower doses of ritonavir boosting. A ritonavir boosting dose of 100 mg can be used for children weighing ≥20 kg, particularly when lower dose formulations are unavailable or if intolerant to the solution.

Post-HAART outcomes in pediatric populations: comparison of resource-limited and developed countries

CONTEXT

No formal comparison has been made between the pediatric post-highly active antiretroviral therapy (HAART) outcomes of resource-limited and developed countries.

OBJECTIVE

To systematically quantify and compare major baseline characteristics and clinical end points after HAART between resource-limited and developed settings.

METHODS

Published articles and abstracts (International AIDS Society 2009, Conference on Retroviruses and Opportunistic Infections 2010) were examined from inception (first available publication for each search engine) to March 2010. Publications that contained data on post-HAART mortality, weight-for-age z score (WAZ), CD4 count, or viral load (VL) changes in pediatric populations were reviewed. Selected studies met the following criteria: (1) patients were younger than 21 years; (2) HAART was given (≥ 3 antiretroviral medications); and (3) there were >20 patients. Data were extracted for baseline age, CD4 count, VL, WAZ, and mortality, CD4 and virologic suppression over time. Studies were categorized as having been performed in a resource-limited country (RLC) or developed country (DC) on the basis of the United Nations designation. Mean percentage of deaths per cohort and deaths per 100 child-years, baseline CD4 count, VL, WAZ, and age were calculated for RLCs and DCs and compared by using independent samples t tests.

RESULTS

Forty RLC and 28 DC publications were selected (N = 17 875 RLCs; N = 1835 DC). Mean percentage of deaths per cohort and mean deaths per 100 child-years after HAART were significantly higher in RLCs than DCs (7.6 vs 1.6, P < .001, and 8.0 vs 0.9, P < .001, respectively). Mean baseline CD4% was 12% in RLCs and 23% in DCs (P = .01). Mean baseline VLs were 5.5 vs 4.7 log(10) copies per mL in RLCs versus DCs (P < .001).

CONCLUSIONS

Baseline CD4% and VL differ markedly between DCs and RLCs, as does mortality after pediatric HAART. Earlier diagnosis and treatment of pediatric HIV in RLCs would be expected to result in better HAART outcomes.

Boosted protease inhibitors as a therapeutic option in the treatment of HIV-infected children

OBJECTIVE

Paediatric HIV treatment must address various special considerations. Administration of pharmacokinetically enhanced protease inhibitors (PIs) can improve paediatric therapeutic outcomes. The objective of this study was to review the use of boosted PI regimens in children.

METHODS

Systematic literature searches of published manuscripts and conference databases using generic drug names and specific keywords were performed to ensure thorough and balanced reporting of available data.

RESULTS

Boosted PI regimens offer multiple options across a range of ages and are efficacious in naïve and experienced children; safety and tolerability are similar to those observed in adults. Novel boosted PI simplification approaches may foster adherence and diminish resistance.

CONCLUSIONS

Boosted PIs are key components of first- and second-line treatments in children. Identifying factors associated with the response to highly active antiretroviral therapy in children may ultimately permit individualized therapies.

Generic and low dose antiretroviral therapy in adults and children: implication for scaling up treatment in resource limited settings

Although access to antiretroviral therapy (ART) for the treatment of HIV has increased during the last decade, many patients are still in need of treatment. With limited funds to provide ART to millions of patients worldwide, there is a need for alternative ways to scale up ART in resource limited settings. This review provides an overview of pharmacokinetic, safety and efficacy studies of generic and reduced dose ART. The production of generic ART has greatly influenced the decline in drug prices and the increased in ART access. Generic ART has good pharmacokinetic profile, safety and efficacy. Toxicity is however the main cause for ART discontinuation. Several dose reduction studies have shown adequate pharmacokinetic parameters and short term efficacy with reduced dose ART. Ethnicity may affect drug metabolism; several pharmacokinetic studies have confirmed higher plasma ART concentration in Asians. Randomized efficacy trial of reduced versus standard ART is warranted.

HAART for children with treatment failure

Even as pediatric rollout programs are struggling to meet global need, increasing numbers of children are failing first-line antiretroviral therapy in low- and middle-income countries. Without better access to viral load monitoring, second-line antiretrovirals and research to guide optimal regimen selection, it will be difficult to ensure that HIV-infected children will survive into adulthood. Data available on pediatric drug resistance demonstrate that failure occurs early in childhood. Studies of salvage drug options have been promising, but are primarily conducted in adults. Evidence-based approaches to regimen selection, pediatric antiretroviral formulations and expanded access to novel drugs are now required to prepare for the future.

Indinavir/ritonavir remains an important component of HAART for the treatment of HIV/AIDS, particularly in resource-limited settings

For over a decade, indinavir has been approved for the treatment of HIV/AIDS; however, following the introduction of new protease inhibitors (PIs) with improved safety and pharmacologic profiles, its use in developed countries has become almost obsolete. In contrast, in resource-limited settings where the majority of people living with HIV/AIDS reside, indinavir is part of the most affordable PI-based highly active antiretroviral treatment regimen. A major drawback of indinavir use is renal toxicity, but low-dose indinavir plus ritonavir (400/100 mg) twice daily is both efficacious and tolerable. Similar low dosing levels in children have also proven successful, but data in pregnant women remains limited. Due to its low cost and proven efficacy indinavir remains a key component of HIV/AIDS treatment in resource-limited settings.