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

Abacavir versus Zidovudine-based regimens for treatment of HIV-infected children in resource limited settings: a retrospective cohort study

BACKGROUND

Abacavir (ABC) and Zidovudine (AZT) based regimens are the preferred first line nucleoside reverse transcriptase (NRTIs) backbones being widely utilized for managing HIV infection in children. However, there is a dearth of data regarding the clinical outcomes and associated risk factors in Ethiopia. We compared the proportion of mortality and the rate of occurrence of Opportunistic Infections (OIs) with ABC versus AZT -based regimens in a cohort of HIV-infected children.

METHODS

A 42 months retrospective cohort study was conducted. A total of 179 records were reviewed by including data from October 2014 to April 2017. Data were collected on socio-demographic, clinical characteristics of patients and drug related variables. Data were analyzed using STATA13.1. Kaplan-Meier and Cox regression were used to compare survival experience and identify independent predictors. Propensity score matching analysis was conducted to elucidate the average treatment effects of each regimen over OIs.

RESULT

Of 179 patients, 98 (54.7%) were females. The mean (+SD) age of the study subjects was 6.53 ± 2.83 years. Through 42 months analysis, a total of 4 patients (1 (1.14%) from ABC group and 3 (3.3%) from AZT group (p = 0.339)) were died. The incidence of opportunistic infections attributed to ABC group was 8.77/100,000 person years (py) and that of AZT was 6.9/100,000py. The incidence rate ratio (IRR) for OIs was (IRR = 0.87, 95% CI [0.49-1.53] (p = 0.304). Baseline CD4 count (AHR = 0.99, 95% CI [0.98-0.99]), Severe acute malnutrition (AHR = 15.92, 95% CI [5.34-47.50]), and exposure to tuberculosis treatment (AHR = 2.93, 95% CI [1.39-6.17]) were the independent predictors for the development of OIs.

CONCLUSION

ABC and AZT based ART regimens seem to have comparable survival benefit among HIV-infected children in Ethiopia. Therefore, both regimens might be used as an alternative in resource limited settings.

Effect of First-Line Antituberculosis Therapy on Nevirapine Pharmacokinetics in Children Younger than Three Years Old

Nevirapine-based antiretroviral therapy (ART) is one of the limited options in HIV-infected children younger than 3 years old (young children) with tuberculosis (TB) coinfection. To date, there are insufficient data to recommend nevirapine-based therapy during first-line antituberculosis (anti-TB) therapy in young children. We compared nevirapine pharmacokinetics (PK) in HIV-infected young children with and without TB coinfection. In the coinfected group, nevirapine PK was evaluated while on anti-TB therapy and after completing an anti-TB therapy regimen. Of 53 participants, 23 (43%) had TB-HIV coinfection. While the mean difference in nevirapine PK parameters between the two groups was not significant (P > 0.05), 14/23 (61%) of the children with TB-HIV coinfection and 9/30 (30%) with HIV infection had a nevirapine minimum concentration (Cmin) below the proposed target of 3.0 mg/liter (P = 0.03). In multivariate analysis, anti-TB therapy and the CYP2B6 516G>T genotype were joint predictors of nevirapine PK parameters. Differences in nevirapine PK parameters between the two groups were significant in children with CYP2B6 516GG but not the GT or TT genotype. Among 14 TB-HIV-coinfected participants with paired data, the geometric mean Cmin and area under the drug concentration-time curve from time zero to 12 h (AUC0-12) were about 34% lower when patients were taking anti-TB therapy, while the nevirapine apparent oral clearance (CL/F) was about 45% higher. While the induction effect of anti-TB therapy on nevirapine PK in our study was modest, the CYP2B6 genotype-dependent variability in the TB drug regimen effect would complicate any dose adjustment strategy in young children with TB-HIV coinfection. Alternate ART regimens that are more compatible with TB treatment in this age group are needed. (This study has been registered at ClinicalTrials.gov under identifier NCT01699633.).

Determinants of virological outcome and adverse events in African children treated with paediatric nevirapine fixed-dose-combination tablets

BACKGROUND

Nevirapine is the only nonnucleoside reverse transcriptase inhibitor currently available as a paediatric fixed-dose-combination tablet and is widely used in African children. Nonetheless, the number of investigations into pharmacokinetic determinants of virological suppression in African children is limited, and the predictive power of the current therapeutic range was never evaluated in this population, thereby limiting treatment optimization.

METHODS

We analysed data from 322 African children (aged 0.3-13 years) treated with nevirapine, lamivudine, and either abacavir, stavudine, or zidovudine, and followed up to 144 weeks. Nevirapine trough concentration (Cmin) and other factors were tested for associations with viral load more than 100 copies/ml and transaminase increases more than grade 1 using proportional hazard and logistic models in 219 initially antiretroviral treatment (ART)-naive children.

RESULTS

Pre-ART viral load, adherence, and nevirapine Cmin were associated with viral load nonsuppression [hazard ratio = 2.08 (95% confidence interval (CI): 1.50-2.90, P < 0.001) for 10-fold higher pre-ART viral load, hazard ratio = 0.78 (95% CI: 0.68-0.90, P < 0.001) for 10% improvement in adherence, and hazard ratio = 0.94 (95% CI: 0.90-0.99, P = 0.014) for a 1 mg/l increase in nevirapine Cmin]. There were additional effects of pre-ART CD4 cell percentage and clinical site. The risk of virological nonsuppression decreased with increasing nevirapine Cmin, and there was no clear Cmin threshold predictive of virological nonsuppression. Transient transaminase elevations more than grade 1 were associated with high Cmin (>12.4 mg/l), hazard ratio = 5.18 (95% CI 1.95-13.80, P < 0.001).

CONCLUSION

Treatment initiation at lower pre-ART viral load and higher pre-ART CD4 cell percentage, increased adherence, and maintaining average Cmin higher than current target could improve virological suppression of African children treated with nevirapine without increasing toxicity.

Dose evaluation of lamivudine in human immunodeficiency virus-infected children aged 5 months to 18 years based on a population pharmacokinetic analysis

AIM

The objectives of this study were to characterize age-related changes in lamivudine pharmacokinetics in children and evaluate lamivudine exposure, followed by dose recommendations for subgroups in which target steady state area under the daily plasma concentration-time curve (AUC_0-24h ) is not reached.

METHODS

Population pharmacokinetic modelling was performed in NONMEM using data from two model-building datasets and two external datasets [n = 180 (age 0.4-18 years, body weight 3.4-60.5 kg); 2061 samples (median 12 per child); daily oral dose 60-300 mg (3.9-17.6 mg kg^-1 )]. Steady state AUC_0-24h was calculated per individual (adult target 8.9 mg·h l^-1 ).

RESULTS

A two-compartment model with sequential zero order and first order absorption best described the data. Apparent clearance and central volume of distribution (% RSE) were 13.2 l h^-1 (4.2%) and 38.9 l (7.0%) for a median individual of 16.6 kg, respectively. Bodyweight was identified as covariate on apparent clearance and volume of distribution using power functions (exponents 0.506 (20.2%) and 0.489 (32.3%), respectively). The external evaluation supported the predictive ability of the final model. In 94.5% and 35.8% of the children with a body weight >14 kg and <14 kg, respectively, the target AUC_0-24h was reached.

CONCLUSION

Bodyweight best predicted the developmental changes in apparent lamivudine clearance and volume of distribution. For children aged 5 months-18 years with a body weight <14 kg, the dose should be increased from 8 to 10 mg kg^-1  day^-1 if the adult target for AUC_0-24h is aimed for. In order to identify whether bodyweight influences bioavailability, clearance and/or volume of distribution, future analysis including data on intravenously administered lamivudine is needed.

Effect of diurnal variation, CYP2B6 genotype and age on the pharmacokinetics of nevirapine in African children

OBJECTIVES

To characterize the effects of CYP2B6 polymorphisms, diurnal variation and demographic factors on nevirapine pharmacokinetics in African children.

METHODS

Non-linear mixed-effects modelling conducted in NONMEM 7.3 described nevirapine plasma concentration-time data from 414 children aged 0.3-15 years.

RESULTS

Nevirapine pharmacokinetics was best described using a one-compartment disposition model with elimination through a well-stirred liver model accounting for a first-pass effect and transit-compartment absorption. Intrinsic clearance was affected by diurnal variation (characterized using a cosine function with peak amplitude 29% at 12 noon) and CYP2B6 metabolizer status [extensive metabolizer (EM) 516GG|983TT, reference; intermediate metabolizer (IM) 516GT|983TT or 516GG|983TC, 17% lower; slow metabolizer (SM) 516TT|983TT or 516GT|983TC, 50% lower; ultra-slow metabolizer (USM) 516GG|983CC, 68% lower]. Age was found to affect pre-hepatic bioavailability: 31.7% lower at birth and increasing exponentially. Median (90% CI) evening Cmin values in the different metabolizer groups were 5.01 (3.01-7.47), 6.55 (3.65-13.32), 11.59 (5.44-22.71) and 12.32 (12.32-27.25) mg/L, respectively. Evening Cmin values were <3 mg/L in 43% of EM weighing <6 kg and 26% of IM weighing <6 kg, while 73% of SM and 88% of USM in all weight-bands had evening Cmin values >8 mg/L. Cmin was not markedly affected by administration time, but was altered by unequal splitting of the daily dose.

CONCLUSIONS

Diurnal variation does not greatly affect nevirapine exposure. However, when daily doses cannot be split equally, the larger dose should be given in the morning. To achieve homogeneous exposures, nevirapine doses for SM and USM should be reduced by 50%, and children weighing <6 kg with EM or IM metabolizer status should receive the same dose as children weighing 6-10 kg.

Abacavir, zidovudine, or stavudine as paediatric tablets for African HIV-infected children (CHAPAS-3): an open-label, parallel-group, randomised controlled trial

Background

WHO 2013 guidelines recommend universal treatment for HIV-infected children younger than 5 years. No paediatric trials have compared nucleoside reverse-transcriptase inhibitors (NRTIs) in first-line antiretroviral therapy (ART) in Africa, where most HIV-infected children live. We aimed to compare stavudine, zidovudine, or abacavir as dual or triple fixed-dose-combination paediatric tablets with lamivudine and nevirapine or efavirenz.

Methods

In this open-label, parallel-group, randomised trial (CHAPAS-3), we enrolled children from one centre in Zambia and three in Uganda who were previously untreated (ART naive) or on stavudine for more than 2 years with viral load less than 50 copies per mL (ART experienced). Computer-generated randomisation tables were incorporated securely within the database. The primary endpoint was grade 2–4 clinical or grade 3/4 laboratory adverse events. Analysis was intention to treat. This trial is registered with the ISRCTN Registry number, 69078957.

Findings

Between Nov 8, 2010, and Dec 28, 2011, 480 children were randomised: 156 to stavudine, 159 to zidovudine, and 165 to abacavir. After two were excluded due to randomisation error, 156 children were analysed in the stavudine group, 158 in the zidovudine group, and 164 in the abacavir group, and followed for median 2·3 years (5% lost to follow-up). 365 (76%) were ART naive (median age 2·6 years vs 6·2 years in ART experienced). 917 grade 2–4 clinical or grade 3/4 laboratory adverse events (835 clinical [634 grade 2]; 40 laboratory) occurred in 104 (67%) children on stavudine, 103 (65%) on zidovudine, and 105 (64%), on abacavir (p=0·63; zidovudine vs stavudine: hazard ratio [HR] 0·99 [95% CI 0·75–1·29]; abacavir vs stavudine: HR 0·88 [0·67–1·15]). At 48 weeks, 98 (85%), 81 (80%) and 95 (81%) ART-naive children in the stavudine, zidovudine, and abacavir groups, respectively, had viral load less than 400 copies per mL (p=0·58); most ART-experienced children maintained suppression (p=1·00).

Interpretation

All NRTIs had low toxicity and good clinical, immunological, and virological responses. Clinical and subclinical lipodystrophy was not noted in those younger than 5 years and anaemia was no more frequent with zidovudine than with the other drugs. Absence of hypersensitivity reactions, superior resistance profile and once-daily dosing favours abacavir for African children, supporting WHO 2013 guidelines.

Funding

European Developing Countries Clinical Trials Partnership.

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.

The effect of malnutrition on the pharmacokinetics and virologic outcomes of lopinavir, efavirenz and nevirapine in food insecure HIV-infected children in Tororo, Uganda

BACKGROUND

Malnutrition may impact the pharmacokinetics (PKs) of antiretroviral medications and virologic responses in HIV-infected children. The authors therefore evaluated the PK of nevirapine (NVP), efavirenz (EFV) and lopinavir (LPV) in associations with nutritional status in a cohort of HIV-infected Ugandan children.

METHODS

Sparse dried blood spot samples from Ugandan children were used to estimate plasma concentrations. Historical PK data from children from 3 resource-rich countries (RRC) were utilized to develop the PK models.

RESULTS

Concentrations in 330 dried blood spot from 163 Ugandan children aged 0.7-7 years were analyzed in reference to plasma PK data (1189 samples) from 204 children from RRC aged 0.5-12 years. Among Ugandan children, 48% was malnourished (underweight, thin or stunted). Compared to RRC, Ugandan children exhibited reduced bioavailability of EFV and LPV; 11% (P=0.045) and 18% (P=0.008), respectively. In contrast, NVP bioavailability was 46% higher in Ugandan children (P<0.001) with a trend toward greater bioavailability when malnourished. Children receiving LPV, EFV or NVP had comparable risk of virologic failure. Among children on NVP, low height and weight for age Z scores were associated with reduced risk of virologic failure (P=0.034, P=0.068, respectively).

CONCLUSIONS

Ugandan children demonstrated lower EFV and LPV and higher NVP exposure compared to children in RRC, perhaps reflecting the consequence of malnutrition on bioavailability. In children receiving NVP, the relation between exposure, malnutrition and outcome turned out to be marginally significant. Further investigations are warranted using more intensive PK measurements and adequate adherence assessments, to further assess causes of virologic failure in Ugandan 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) .

Chronic ethanol use in alcoholic beverages by HIV-infected patients affects the therapeutic window of stavudine, lamivudine and nevirapine during the 9-month follow-up period: using chronic alcohol-use biomarkers

Abstract Background: Chronic ethanol use is a global problem including among HIV-infected patients on stavudine/lamivudine/nevirapine (d4T/3TC/NVP) regimen. The study determined the effect of chronic ethanol use on the therapeutic window of d4T, 3TC and NVP in HIV-infected patients using alcohol-use biomarkers to screen patients for chronic ethanol use. Methods: A case-control study using repeated measures design with serial measurements was used to quantify drugs in plasma. The WHO alcohol use disorder identification test (AUDIT) tool was initially used to screen patients for chronic alcohol use, and then they were further sorted using alcohol-use bioamarkers (γ-glutamyl transferase ≥55.0 IU; mean corpuscular volume, ≥96 fl, aspartate amino transferase/alanine aminotransferase ratio ≥2.0 value). A total of 41 patients (26 in the alcohol group and 15 in the control group) were followed up for 9 months with blood sampling done at 3-month intervals. Plasma drug concentrations were quantified using a Shimadzu Class-VP™ HPLC data system version 6.1. Data was analyzed using SAS 2003 version 9.1 statistical package with repeated measures fixed model. Means were compared using Student's t-test. Results: The mean steady-state plasma drug concentrations of d4T and 3TC in the alcohol group were lower than that in the control group during the 9-month period of follow-up. For 3TC, there was a statistical difference in the mean steady-state plasma drug concentrations between the alcohol group and the control group (p≤0.05) in the 6- and 9-month period of follow-up. For NVP, in both groups they were within the reference ranges, although the drug plasma concentrations were higher in the alcohol group compared to the control group and were statistically significant (p<0.05) in 0, 3 and 6 months of follow-up. Conclusions: Chronic ethanol use by HIV-infected patients reduced the therapeutic steady-state plasma drug concentrations of d4T and 3TC and increased the NVP drug concentrations in the HIV-infected patients.

Prevalence and determinants of virological failure in HIV-infected children on antiretroviral therapy in rural Cameroon: a cross-sectional study

BACKGROUND

In Africa, success of antiretroviral treatment (ART) seems to lag behind in children compared with adults, and high therapeutic failure rates have been reported. We aimed to identify prevalence and determinants of virological failure in HIV-infected children treated under programmatic conditions.

METHODS

All patients <18 years on ART presenting to the HIV clinic at the Bamenda Regional Hospital, a secondary referral hospital in rural Cameroon, from September 2010 to August 2011, were enrolled in this cross-sectional study. Clinical data, self-reported adherence, CD4(+) T-cell counts and viral load were recorded. Therapeutic drug monitoring was performed on stored plasma samples. Determinants of virological failure were identified using descriptive statistics and logistic regression.

RESULTS

A total of 230 children with a mean age of 8.9 years (sd 3.7) were included. At the time of analysis, the mean duration of HAART was 3.5 years (sd 1.7) and 12% had a CD4(+) T-cell count <200 cells/µl. In total, 53% of children experienced virological failure (>200 copies/ml). Among children on nevirapine (NVP), plasma levels were subtherapeutic in 14.2% and supratherapeutic in 42.2%. Determinants of virological failure included male sex, lower CD4(+) T-cell counts, subtherapeutic drug levels, longer time on ART and a deceased mother. Poor adherence was associated with subtherapeutic NVP plasma levels and advanced disease stages (WHO stage 3/4).

CONCLUSIONS

This study demonstrates high virological failure rates and a high variability of NVP plasma levels among HIV-infected children in a routine ART programme in rural Cameroon. Strategies to improve adherence to ART in HIV-infected children are urgently needed.

The needs for HIV treatment and care of children, adolescents, pregnant women and older people in low-income and middle-income countries

OBJECTIVE

Success in diagnosing and treating HIV-infected adults has, where HIV care and treatment is available, turned HIV into a chronic, rather than life-limiting disease. Progress meeting the needs of HIV-infected children, perinatally and horizontally infected adolescents, pregnant women and older people has lagged behind. We review the special needs and barriers to scaling up care and antiretroviral therapy (ART) coverage in these populations.

DESIGN AND METHODS

A literature review combined with personal views and operational experience specifically from countries covered by the Evidence for Action programme.

RESULTS

Challenges include logistics of diagnosis and treatment in pregnancy, difficulties in early infant diagnosis, availability of appropriate paediatric formulations, management of adolescents, and comorbidities in older people.

CONCLUSION

Priorities for development need to focus upon the simplification of HIV care to allow provision for all ages at the primary healthcare level. Specific priorities include focused use of virological testing in infants, ongoing development of dispersible and scored fixed-dose ART combinations suitable for use across ages, development of 'adolescent-friendly' HIV services catering for perinatally and horizontally infected adolescents to improve adherence and reduce onward transmissions, simplification of referral pathways to ensure all pregnant women are tested for HIV and commenced on ART, and education of healthcare workers on the specific needs of HIV care in older patients. Each priority will be reviewed and potential solutions discussed.

Pharmacokinetics of nevirapine in HIV-infected infants weighing 3 kg to less than 6 kg taking paediatric fixed dose combination tablets

OBJECTIVES

To evaluate pharmacokinetics of nevirapine, lamivudine and stavudine in HIV-infected Zambian infants receiving fixed dose combination (FDC) antiretroviral tablets (Triomune Baby).

DESIGN

Phase I/II study.

METHODS

Sixteen HIV-infected children at least 1 month, weighing 3 kg to less than 6 kg were enrolled. Blood was sampled at t = 0, 2, 6 and 12 h after observed intake of one FDC tablet (50 mg nevirapine, 6 mg stavudine, 30 mg lamivudine) 4 weeks after starting treatment. Safety and viral load response over 48 weeks were determined.

RESULTS

The median [interquartile range (IQR)] age, body weight and daily nevirapine dose in 15 included children (eight girls) were 4.8 (4.2, 8.4) months, 5.3 (4.3, 5.5) kg and 348 (326 385) mg/m, respectively. The median (IQR) nevirapine area under the concentration-time curve (AUC0-12 h), Cmax and C12 h were 70 (56, 104) h mg/l, 7.5 (6.2, 10) mg/l, and 4.3 (2.9, 6.9) mg/l, respectively. Values were on average higher than reported in adults, but approximately 20% lower than previously reported in children weighing at least 6 kg. Four of 15 (27%) children had a subtherapeutic nevirapine C12 h (defined as <3.0 mg/l) compared to only three of 63 (5%) children weighing at least 6 kg (P = 0.02), whereas children aged less than 5 months [three of six (50%)] may have the highest risk for subtherapeutic nevirapine C12 h (P = 0.24). No association was found between viral load values and nevirapine plasma pharmacokinetic parameters (P > 0.3). Stavudine-lamivudine pharmacokinetic parameters were broadly comparable to heavier children.

CONCLUSION

Exposure to nevirapine in African, HIV-infected infants with low body weight taking FDC tablets appears on average to be adequate, but due to large intersubject variability a relatively high proportion had subtherapeutic nevirapine C12 h levels, particularly those aged less than 5 months.

Nevirapine exposure with WHO pediatric weight band dosing: enhanced therapeutic concentrations predicted based on extensive international pharmacokinetic experience

Nevirapine (NVP) is a nonnucleoside reverse transcriptase inhibitor (NNRTI) used worldwide as part of combination antiretroviral therapy in infants and children to treat HIV infection. Dosing based on either weight or body surface area has been approved by the U.S. Food and Drug Administration (FDA) but can be difficult to implement in resource-limited settings. The World Health Organization (WHO) has developed simplified weight band dosing for NVP, but it has not been critically evaluated. NVP pharmacokinetic data were combined from eight pediatric clinical trials (Pediatric AIDS Clinical Trials Group [PACTG] studies 245, 356, 366, 377, 403, 1056, and 1069 and Children with HIV in Africa Pharmacokinetics and Adherence of Simple Antiretroviral Regimens [CHAPAS]) representing subjects from multiple continents and across the pediatric age continuum. A population pharmacokinetic model was developed to characterize developmental changes in NVP disposition, identify potential sources of NVP pharmacokinetic variability, and assess various pediatric dosing strategies and their impact on NVP exposure. Age, CYP2B6 genotype, and ritonavir were independent predictors of oral NVP clearance. The Triomune fixed-dose tablet was an independent predictor of bioavailability compared to the liquid and other tablet formulations. Monte Carlo simulations of the final model were used to assess WHO weight band dosing recommendations. The final pharmacokinetic model indicated that WHO weight band dosing is likely to result in a percentage of children with NVP exposure within the target range similar to that obtained with FDA dosing. Weight band dosing of NVP proposed by the WHO has the potential to provide a simple and effective dosing strategy for resource limited settings.

Pharmacokinetics of nevirapine in HIV-infected children under 3 years on rifampicin-based antituberculosis treatment

OBJECTIVE

There is an urgent need to optimize cotreatment for children with tuberculosis and HIV infection. We described nevirapine pharmacokinetics in Zambian children aged less than 3 years, cotreated with nevirapine, lamivudine and stavudine in fixed-dose combination (using WHO weight bands) and rifampicin-based antituberculosis treatment.

DESIGN

Twenty-two children received antituberculosis and antiretroviral therapy (ART) concurrently for 4 weeks before pharmacokinetic sampling. Plasma nevirapine concentrations were determined in samples taken immediately before, and 1, 2 and 6 h after an observed dose. Nevirapine pharmacokinetics were compared with those in 16 children aged less than 3 years without tuberculosis.

RESULTS

Twenty-two children were treated for HIV/TB coinfection, 10 of whom were girls. One boy was excluded from analysis for nonadherence. The median age was 1.6 years (range: 0.7-3.2). Median weight was 8.0 kg (range: 5.1-10.5). The baseline CD4% was 13.1 (range: 3.9-43.6). Median predose concentration of nevirapine was 2.93 mg/l (range: 1.06-11.4), and peak concentration was 6.33 mg/l (range: 2.61-14.5). The nevirapine AUC up to 12 h was estimated as 52.0 mg.h/l (range: 22.6-159.7) compared with 90.9 mg.h/l (range: 40.4-232.1) in children without tuberculosis (P < 0.001). Predose concentrations of nevirapine were less than 3.0 mg/l in 11 children on tuberculosis treatment versus none of the 16 children without tuberculosis treatment (P = 0.001). AUC was 41% (95% CI: 23-54%) lower in children with tuberculosis than without tuberculosis (P < 0.001) after adjusting for dose per square meter.

CONCLUSION

: We found substantial reductions in nevirapine concentrations in young children receiving rifampicin. Further studies are needed to define the pharmacokinetics, safety and efficacy of adjusted doses of nevirapine-based ART in young children with tuberculosis.

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.

Involvement of consumers in studies run by the Medical Research Council Clinical Trials Unit: results of a survey

BACKGROUND

We aimed to establish levels of consumer involvement in randomised controlled trials (RCTs), meta-analyses and other studies carried out by the UK Medical Research Council (MRC) Clinical Trials Unit across the range of research programs, predominantly in cancer and HIV.

METHODS

Staff responsible for studies that were included in a Unit Progress Report (MRC CTU, April 2009) were asked to complete a semi-structured questionnaire survey regarding consumer involvement. This was defined as active involvement of consumers as partners in the research process and not as subjects of that research. The electronic questionnaires combined open and closed questions, intended to capture quantitative and qualitative information on whether studies had involved consumers; types of activities undertaken; recruitment and support; advantages and disadvantages of involvement and its perceived impact on aspects of the research.

RESULTS

Between October 2009 and April 2010, 138 completed questionnaires (86%) were returned. Studies had been conducted over a 20 year period from 1989, and around half were in cancer; 30% in HIV and 20% were in other disease areas including arthritis, tuberculosis and blood transfusion medicine. Forty-three studies (31%) had some consumer involvement, most commonly as members of trial management groups (TMG) [88%]. A number of positive impacts on both the research and the researcher were identified. Researchers generally felt involvement was worthwhile and some felt that consumer involvement had improved the credibility of the research. Benefits in design and quality, trial recruitment, dissemination and decision making were also perceived. Researchers felt they learned from consumer involvement, albeit that there were some barriers.

CONCLUSIONS

Whilst most researchers identified benefits of involving consumers, most of studies included in the survey had no involvement. Information from this survey will inform the development of a unit policy on consumer involvement, to guide future research conducted within the MRC Clinical Trials Unit and beyond.

Antiretroviral therapy for children in resource-limited settings: current regimens and the role of newer agents

WHO antiretroviral treatment guidelines for HIV-infected children have influenced the design of treatment programmes in resource-limited settings. This review analyses the latest WHO first- and second-line regimen recommendations. The recommendation to use lopinavir/ritonavir-containing first-line regimens in young children with prior non-nucleoside reverse transcriptase inhibitor (NNRTI) exposure is based on good quality evidence. Recent research suggests that lopinavir/ritonavir-containing first-line regimens should be extended to all young children, irrespective of prior NNRTI exposure. Strategies for overcoming the adverse metabolic effects of rifampicin-containing anti-tuberculosis therapy on antiretroviral therapy regimens have been under-researched in HIV-infected children, creating uncertainty about global recommendations. Preferred second-line recommendations are largely predictable. The exception is that NNRTI-containing second-line regimens are recommended for children previously exposed to NNRTIs and who subsequently did not respond to lopinavir/ritonavir-containing first-line therapy. In these patients, second-line regimens containing newer protease inhibitors (PIs) such as darunavir and tipranavir, or integrase inhibitors such as raltegravir, should be evaluated. Newer antiretroviral agents including second-generation NNRTIs and PIs, C-C chemokine receptor type 5 inhibitors, and integrase inhibitors may assist in further refinement of existing regimen options.

Palatability, adherence and prescribing patterns of antiretroviral drugs for children with human immunodeficiency virus infection in Canada

PURPOSE

To assess the impact of perceived palatability of antiretroviral drugs on adherence to therapy of children infected by human immunodeficiency virus and on prescribing patterns by their caring physicians.

METHODS

DESIGN

Two arms--retrospective chart review and a cross-sectional survey.

SETTING

Tertiary-care pediatric human immunodeficiency virus clinic during a 17-year period.

PARTICIPANTS

Children with human immunodeficiency virus infection and physicians actively caring for children with human immunodeficiency virus infection in seven provinces in Canada were surveyed regarding their perception of the palatability of 8-liquid and 15 non-liquid antiretroviral medications and its effect on drug selection.

MAIN OUTCOME MEASURE

Effect of taste preferences of antiretroviral drugs on adherence to treatment by infected children and on drug selection by their caring physicians.

RESULTS

Forty of 119 children (34%) refused at least once to an antiretroviral medication. In 5%, treatment was discontinued because of poor palatability. Ritonavir was the least palatable drug (50% of children; p = 0.01). Ritonavir use (OR 4.80 [95%CI 1.34-17.20]) and male gender (OR 7.25 [95%CI 2.30-22.90]) were independent predictors of drug discontinuation because of poor taste. Physicians also perceived liquid ritonavir as the least palatable (p = 0.01) and the most likely to be discontinued (p = 0.01). However, they commonly prescribed it as first-line therapy (p = 0.06).

CONCLUSIONS

A third of children infected with human immunodeficiency virus fail to adhere to their treatment because of poor drug taste. Physicians are aware of that, but this does not prevent them from selecting the least palatable drugs as first-line therapy.

Pharmacogenetics of toxicity, plasma trough concentration and treatment outcome with nevirapine-containing regimen in anti-retroviral-naïve HIV-infected adults: an exploratory study of the TRIANON ANRS 081 trial

The aim of this exploratory study was to investigate in a homogeneous population of anti-retroviral naïve HIV-1-infected adults, the relationships between genetic polymorphisms involved in nevirapine metabolism [CYP2B6 516G>T, 785A>G and 1459C>T; CYP3A5 6986A>G (CYP3A5*3)], transport (ABCB1 2677G>T/A and 3435C>T), and antigen recognition (HLA-DRB1*0101), and the hepatic and/or cutaneous toxicity occurring within the first 8 or 72 weeks of treatment, plasma trough concentrations (C(trough) ) at week 8 and immuno-virological response to nevirapine at week 24. Associations between genetic polymorphisms and toxicity, C(trough) and response to nevirapine were performed in a population of 72 HIV-1 positive and nevirapine-treated patients followed during 72 weeks, as part of the previous study called: ANRS081 'Trianon' trial. Among the 18 patients who developed toxicity events during the 72 weeks of the study, 12 patients exhibited early toxicity before week 8. No significant association could be evidenced between any of the analysed single nucleotide polymorphisms (SNPs) and nevirapine early or global toxicity, pharmacokinetics and immuno-virological responses even though a possible association between CYP2B6 516G>T and 1459C>T and the trough level of nevirapine was suggested.

Antiretroviral drugs in pediatric HIV-infected patients: pharmacokinetic and practical challenges

Antiretroviral (ARV) therapy has been shown to achieve high therapeutic efficacy in treating pediatric HIV disease. The delivery of affordable, child friendly, and easy to store and administer ARV drugs is key to the successful management of HIV in children. In recent years, significant progress has been made in scaling up the access to pediatric ARV therapy among children worldwide. Despite the improved ARV drug access, multiple challenges remain concerning palatability and efficient delivery of ARV drugs to children from infancy into adolescence. Data are limited regarding developmental changes in pharmacokinetics of individual ARV drugs, and pediatric and adult fixed-dose combinations. This review provides a practical discussion regarding the pharmacokinetics of ARV agents in pediatric HIV-infected patients, as well as the practical challenges of currently available formulations, such as palatability of liquid formulations, challenges of crushing tablets, and using adult and pediatric fixed-dose combinations.

Pharmacology and immuno-virologic efficacy of once-a-day HAART in African HIV-infected children: ANRS 12103 phase II trial

OBJECTIVE

To assess 12-month survival, pharmacokinetics, immunologic and virologic efficacy, tolerance, compliance and drug resistance in HIV-infected children in Bobo-Dioulasso, Burkina Faso, receiving once-daily highly-active antiretroviral therapy as a combination of didanosine (DDI), lamivudine (3TC) and efavirenz (EFV).

METHODS

In the ANRS 12103 open phase II trial, HIV-infected children were examined at inclusion and monthly thereafter. CD4+ T-lymphocyte (CD4) count, plasma concentration of ribonucleic acid (RNA) of human immunodeficiency virus type 1 (HIV-1) and haematologic and biochemical parameters were measured at baseline and every trimester. HIV-1 resistance testing was performed in case of viral escape. Drug plasma concentrations were determined with high-performance liquid chromatography.

FINDINGS

From February 2006 to November 2007, 51 children (39% girls) with a mean age of 6.8 years were enrolled and treated for 12 months. At baseline, Z scores for mean weight-for-age and mean height-for-age were -2.01 and -2.12, respectively. Mean CD4% was 9.0. Median plasma HIV-1 RNA viral load was 5.51 log(10) copies per millilitre (cp/ml). Two children (3.9%) died and another 11 (22%) suffered 13 severe clinical events. At month 12, mean WAZ had improved by 0.63 (P < 0.001) and mean HAZ by 0.57 (P < 0.001). Mean CD4% had risen to 24 (P < 0.001). Viral load was below 300 RNA cp/ml in 81% of the children; HIV resistance mutations were detected in 11 (21.6%).

CONCLUSION

The once-a-day combination of DDI + 3TC + EFV is an alternative first-line treatment for HIV-1-infected children. Dose adjustment should further improve efficacy.

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.

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.

Limited sampling models to predict the pharmacokinetics of nevirapine, stavudine, and lamivudine in HIV-infected children treated with pediatric fixed-dose combination tablets

Full 12-hour pharmacokinetic profiles of nevirapine, stavudine, and lamivudine in HIV-infected children taking fixed-dose combination antiretroviral tablets have been reported previously by us. Further studies with these formulations could benefit from less-intensive pharmacokinetic sampling. Data from 65 African children were used to relate area under the plasma concentration versus time curve over 12 hours (AUC) to plasma concentrations of nevirapine, stavudine, or lamivudine at times t = 0, 1, 2, 4, 6, 8, and 12 hours after intake using linear regression. Limited sampling models were developed using leave-one-out crossvalidation. The predictive performance of each model was evaluated using the mean relative prediction error (mpe%) as an indicator of bias and the root mean squared relative prediction error (rmse%) as a measure of precision. A priori set criteria to accept a limited sampling model were: 95% confidence limit of the mpe% should include 0, rmse% less than 10%, a high correlation coefficient, and as few (convenient) samples as possible. Using only one sample did not lead to acceptable AUC predictions for stavudine or lamivudine, although the 6-hour sample was acceptable for nevirapine (mpe%: -0.8%, 95% confidence interval: -2.2 to +0.6); rmse%: 5.8%; r: 0.98). Using two samples, AUC predictions for stavudine and lamivudine improved considerably but did not meet the predefined acceptance criteria. Using three samples (1, 2, 6 hours), an accurate and precise limited sampling model for stavudine AUC (mpe%: -0.6%, 95% confidence interval: -2.2 to +1.0; rmse%: 6.5%; r: 0.98) and lamivudine AUC (mpe%: -0.3%, 95% confidence interval: -1.7 to +1.1; rmse%: 5.6%; r: 0.99) was found; this model was also highly accurate and precise for nevirapine AUC (mpe%: -0.2%, 95% confidence interval: -1.0 to +0.7; rmse%: 3.4%; r: 0.99). A limited sampling model using three time points (1, 2, 6 hours) can be used to predict nevirapine, stavudine, and lamivudine AUC accurately and precisely in HIV-infected African children.

Is the recommended once-daily dose of lamivudine optimal in West African HIV-infected children?

We aimed in this study to describe lamivudine concentration-time courses in treatment-naïve children after once-daily administration, to study the effects of body weight and age on lamivudine pharmacokinetics, and to simulate an optimized administration scheme. For this purpose, lamivudine concentrations were measured in 49 children after at least 2 weeks of didanosine-lamivudine-efavirenz treatment. A total of 148 plasma lamivudine concentrations were measured, and a population pharmacokinetic model was developed with NONMEM. The influence of individual characteristics was tested using a likelihood ratio test. Children were divided into two groups, according to their pharmacokinetic parameters, thanks to tree regression analysis. For each patient, the area under the curve was derived from estimated individual pharmacokinetic parameters. Different once-daily doses were simulated in each group, to obtain the same exposure in children as the mean effective exposure in adults (8.9 mg/liter.h). A two-compartment model in which the slope of distribution is assumed to be equal to the absorption rate constant adequately described the data. Parameter estimates were standardized for a mean standard body weight using an allometric model. Children were then divided into 2 groups according to body weight: CL/F was significantly higher in children weighing less than 17 kg (1.12 liters/h/kg) than in children over 17 kg (0.95 liters/h/kg; P=0.01). The target mean AUC of 8.9 mg/liters.h was obtained with a 10-mg/kg once-daily lamivudine (3TC) dose for children below 17 kg; the recommended dose of 8 mg/kg seems to be sufficient in children weighing more than 17 kg. These assumptions should be prospectively confirmed.

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.

Antiretroviral therapy outcomes in resource-limited settings for HIV-infected children <5 years of age

OBJECTIVE

We describe medium-term outcomes for young children receiving antiretroviral therapy (ART) in resource-limited countries.

METHODS

Analyses were conducted on surveillance data for children <5 years of age receiving ART (initiated April 2002 to January 2008) in 48 HIV/AIDS treatment programs in Africa and Asia. Primary outcome measures were probability of remaining in care, probability of developing World Health Organization stage 4 clinical events, rate of switching to second-line ART, and drug toxicity, compared at 6, 12, 24, and 36 months of ART.

RESULTS

Of 3936 children (90% in Africa) initiating ART, 9% were <12 months, 50% were 12 to 35 months, and 41% were 36 to 59 months of age. The median time of ART was 10.5 months. Probabilities of remaining in care after 12, 24, and 36 months of ART were 0.85, 0.80, and 0.75, respectively. Compared with children 36 to 59 months of age at ART initiation, probabilities of remaining in care were significantly lower for children <12 months of age. Overall, 55% and 69% of deaths and losses to follow-up occurred in the first 3 and 6 months of ART, respectively. Probabilities of developing stage 4 clinical events after 12, 24, and 36 months of ART were 0.03, 0.06, and 0.09, respectively. Only 33 subjects (0.8%) switched to second-line regimens, and 151 (3.8%) experienced severe drug toxicities.

CONCLUSIONS

Large-scale ART for children <5 years of age in resource-limited settings is feasible, with encouraging clinical outcomes, but efforts should be increased to improve early HIV diagnosis and treatment.

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.

Response to antiretroviral therapy in HIV-infected Ugandan children exposed and not exposed to single-dose nevirapine at birth

OBJECTIVE

To compare the response to a nevirapine (NVP)-based highly active antiretroviral therapy (HAART) in HIV-infected Ugandan children, exposed and nonexposed to single-dose NVP (sd NVP) at birth.

METHODS

HIV-infected study children were initiated on stavudine/lamivudine/NVP as a fixed dose combination. CD4 cell percent and HIV-1 RNA were documented at baseline, 12, 24, 36, and 48 weeks post-initiation of HAART.

RESULTS

Ninety-two children were enrolled in the study, 44 in the sd NVP-exposed and 48 in the nonexposed cohort. The median age at enrollment was 1.7 years [interquartile range (IQR) 1.2-2.4] and 7.8 years (IQR 5.9-9.2) in the sd NVP-exposed and nonexposed cohorts,respectively (P < 0.001). At baseline and week 48 post-HAART, the median CD4 cell percentages were 14% and 33% for the NVP-exposed group and 8% and 22.5% in the nonexposed group (P < 0.0001). The median (IQR) viral load at baseline was 650,568 (359,979-2,086,613) RNA copies/mL and 239,027 (105,904-494,813) RNA copies/mL in the NVP-exposed and nonexposed cohorts, respectively. After 48 weeks of HAART, 76% of the NVP-exposed and 80% of the nonexposed children had a median viral load of < 400 copies/mL (P = 0.74).

CONCLUSIONS

Both HIV-infected Ugandan older infants and children that were exposed and not exposed to sd NVP at birth had favorable treatment outcomes on NVP-containing HAART.

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.

The future of HIV microbicides: challenges and opportunities

HIV microbicides are topical, self-administered products aimed at preventing or reducing HIV infection in women and may represent the most promising strategy for combating the HIV/AIDS epidemic at the present time. Although a safe and effective microbicide has yet to be identified, all products tested in Phase III trials to date have been vaginal gels containing non-specific compounds with modest potency that had to be applied close to the time of sexual intercourse. Issues regarding these early generation products were further complicated by widely publicized cases of halted efficacy trials. However, as a result of each of these challenges, new information and essential lessons have emerged for the field. These lessons have resulted in a meaningful increase in microbicide development efforts focusing on compounds with highly potent and HIV-specific mechanisms of action, combination products, novel formulations, and carefully designed pharmacokinetic and pharmacodynamic evaluations, all of which are reasons for renewed confidence that a safe and effective microbicide is achievable.

Efficacy of non-nucleoside reverse transcriptase inhibitor-based highly active antiretroviral therapy in Thai HIV-infected children aged two years or less

Twenty-six Thai HIV-infected children, aged 2 years or less were prospectively enrolled to receive non-nucleoside reverse transcription inhibitor-based highly active antiretroviral therapy (HAART). Twenty-two children (85%) had World Health Organization clinical stage 3 or 4. The median baseline CD4 cell percentage and plasma HIV RNA were 17% and 5.9 log 10 copies/mL, respectively. The median age at HAART initiation was 9.8 months (range, 1.5-24.0). One child died. The mean CD4 cell percentages at 24, 48, and 96 weeks of treatment were 26%, 31%, and 37%, respectively. The proportions of children with virologic suppression (<400 copies/mL) at week 24 and 48 were 14/26 (54%) and 19/26 (73%), respectively. Non-nucleoside reverse transcription inhibitor-based HAART is safe and effective in HIV-infected young children in a resource-limited setting.

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.