Pharmacokinetics of anti-TB drugs in Malawian children: reconsidering the role of ethambutol

Background Current guidelines for dosing of anti-TB drugs in children advocate higher doses for rifampicin and isoniazid despite limited availability of paediatric data on the pharmacokinetics of these drugs, especially from Africa, where the burden of childhood disease remains high. Methods Thirty children aged 6 months to 15 years underwent intensive pharmacokinetic sampling for first-line anti-TB drugs at Queen Elizabeth Central Hospital, Blantyre, Malawi. Rifampicin, isoniazid, pyrazinamide and ethambutol were dosed at 10, 5, 25 and 20 mg/kg, respectively. Plasma drug concentrations were determined using sensitive, validated bioanalytical methods and summary pharmacokinetic parameters were estimated using non-compartmental analysis. Results The median (IQR) Cmax was 2.90 (2.08–3.43), 3.37 (2.55–4.59), 34.60 (32.30–40.90) and 1.20 (0.85–1.68) mg/L while the median (IQR) AUC0–∞ was 16.92 (11.10–22.74), 11.48 (7.35–18.93), 333.50 (279.50–487.2) and 8.65 (5.96–11.47) mg·h/L for rifampicin, isoniazid, pyrazinamide and ethambutol, respectively. For all drugs, pharmacokinetic parameters relating to drug absorption and exposure were lower than those published for adults, though similar to existing paediatric data from sub-Saharan Africa. Weight and/or dose predicted at least one measure of exposure for all drugs. Age-related decreases in CL/F for rifampicin and pyrazinamide and a biphasic elimination pattern of isoniazid were observed. Predicted AUC0–∞ for rifampicin dosed at 15 mg/kg was comparable to that of adults while the dose required to achieve ethambutol exposure similar to that in adults was 55 mg/kg or higher. Conclusions These data support recently revised WHO recommendations for dosing of anti-TB drugs in children, but dosing of ethambutol in children also appears inadequate by comparison with adult pharmacokinetic data

Seasonal Intermittent Preventive Treatment for the Prevention of Anaemia and Malaria in Ghanaian Children: A Randomized, Placebo Controlled Trial

BACKGROUND: Malaria and anaemia are the leading causes of morbidity and mortality in children in sub-Saharan Africa. We have investigated the effect of intermittent preventive treatment with sulphadoxine-pyrimethamine or artesunate plus amodiaquine on anaemia and malaria in children in an area of intense, prolonged, seasonal malaria transmission in Ghana. METHODS: 2451 children aged 3-59 months from 30 villages were individually randomised to receive placebo or artesunate plus amodiaquine (AS+AQ) monthly or bimonthly, or sulphadoxine-pyrimethamine (SP) bimonthly over a period of six months. The primary outcome measures were episodes of anaemia (Hb1 year old when they received IPTc compared to the placebo group. However the incidence of malaria in the post intervention period was higher in children who were <1 year old when they received AS+AQ monthly compared to the placebo group. INTERPRETATION: IPTc is safe and efficacious in reducing the burden of malaria in an area of Ghana with a prolonged, intense malaria transmission season. TRIAL REGISTRATION: ClinicalTrials.gov NCT00119132

Plasmodium falciparum: PCR detection and genotyping of isolates from peripheral, placental, and cord blood of pregnant Malawian women and their infants

Polymerase chain reaction (PCR) is both a sensitive means of detecting malaria parasitaemia, and a simple tool for identifying genetic differences in parasites infecting human subjects. We compared PCR to microscopy in detection of Plasmodium falciparum infection in peripheral, placental and cord blood samples collected from 131 pregnant Malawian women and their infants in 1997-99. Infections detected by species-specific PCR were genotyped at the merozoite surface protein I and 2 loci, and minimum numbers of infecting genotypes determined. PCR was of similar sensitivity to microscopy in detecting peripheral and placental infection, and placental blood PCR was 100% specific compared to placental histology. Cord blood parasitaemia was more frequently detected by PCR than microscopy, 20% versus 6%. Genotype numbers in peripheral blood (mean 2-36; range 1-5), placental blood (mean 2-41; range 1-6) and cord (mean 2.14; range 1-4) were similar. The frequency of detection of each allelic family did not differ between sites. Genotypes from different sites in each patient were compared. In 69% of women, genotypes were detected in peripheral blood and not placenta, or vice versa, suggesting possible differential sequestration of different parasite populations. Cord blood genotypes were usually a subset of those in peripheral and placental blood, but, in some cases, genotypes were found in cord blood that were absent from the mother. Transplacental infection before term, and clearance of maternal infection, is postulated

Pharmacokinetics of piperaquine and safety profile of dihydroartemisinin-piperaquine co-administered with antiretroviral therapy in malaria-uninfected HIV-positive Malawian adults

There are limited data on the pharmacokinetic and safety profiles of dihydroartemisinin-piperaquine (DHA-PQ) among human immunodeficiency virus infected (HIV+) individuals taking antiretroviral therapy (ART). In a two step (parallel-group) pharmacokinetic trial with intensive blood sampling, we compared area under the concentration-time curve (AUC0-28 days) and safety outcomes of piperaquine among malaria-uninfected HIV+ adults. In step 1, half the adult dose of DHA-PQ was administered for three days as an intitial safety check in four groups (n=6/group) of HIV+ adults (age≥18 years): (i) antiretroviral-naïve, (ii) on nevirapine-based ART, (iii) on efavirenz-based ART, and (iv) on ritonavir-boosted lopinavir-based ART. In step 2, a full adult treatment course of DHA-PQ was administered to a different cohort of participants in three groups: (i) antiretroviral naïve, (ii) on efavirenz-based ART and (iii) on nevirapine-based ART (n=10-15/group). Ritonavir-boosted lopinavir-based ART group was dropped in step 2 due to limited number of participants who were on this second line ART and were eligible for recruitment. Piperaquine's AUC0-28 days in both steps was 43% lower among participants on efavirenz-based ART compared to ART naïve participants. There were no significant differences in AUC0-28 days between the other ART groups and the ART naïve group in each of the two steps. Furthermore, no differences in treatment-emergent clinical and laboratory adverse events were observed across the groups in steps 1 and 2. Although well tolerated at half and full standard adult treatment courses, efavirenz based antiretroviral regimen was associated with reduced piperaquine exposure which may compromise dihydroartemisinin-piperaquine's effectiveness in programmatic settings

Impact of efavirenz, ritonavir-boosted lopinavir and nevirapine based antiretroviral regimens on the pharmacokinetics of lumefantrine and safety of artemether-lumefantrine in falciparum-negative HIV-infected Malawian adults stabilized on antiretroviral therapy

There is conflicting evidence of the impact of commonly used antiretroviral therapies (ARTs) on the pharmacokinetics of lumefantrine and safety profile of artemether-lumefantrine. We compared the area under the concentration-time curve (AUC0-14 days) of lumefantrine and safety profile of artemether-lumefantrine in malaria-negative human immunodeficiency virus (HIV) infected adults in two steps. In step 1, a half-dose adult course of artemether-lumefantrine was administered as a safety check in four groups (n=6/group): (i) antiretroviral-naïve, (ii) on nevirapine-based ART, (iii) on efavirenz-based ART and (iv) on ritonavir-boosted lopinavir-based ART. In step 2, a standard-dose adult course of artemether-lumefantrine was administered to a different cohort in three groups (n=10-15/group): (i) antiretroviral-naïve, (ii) on efavirenz-based ART and (iii) on ritonavir-boosted lopinavir-based ART. In step 1, lumefantrine's AUC0-14 days was 53% [95% CI: 0.27-0.82] lower in the efavirenz-based ART group than the ART-naïve group and was 2.4 [95% CI: 1.58-3.62] and 2.9 [95% CI: 1.75-4.72] times higher in the nevirapine and ritonavir-boosted lopinavir groups, respectively. In step 2, lumefantrine's AUC0-14 days was 1.9 [95% CI: 1.26-3.00] times higher in the ritonavir-boosted lopinavir group and not significantly different between the efavirenz- and ART-naïve groups (0.99 [95% CI: 0.63-1.57]). Frequent cases of haematological abnormalities (thrombocytopenia and neutropenia) were observed in the nevirapine group in step 1, leading to a recommendation from the data and safety monitoring board not to include a nevirapine group in step 2. Artemether-lumefantrine was well tolerated in the other groups. The therapeutic implications of these findings need to be evaluated among HIV-malaria co-infected adults

Pharmacokinetics and safety profile of artesunate-amodiaquine co-administered with antiretroviral therapy in malaria uninfected HIV-positive Malawian adults

There are limited data on the pharmacokinetic and safety profiles of artesunate-amodiaquine in human immnunodeficiency virus infected (HIV+) individuals receiving antiretroviral therapy. In a two-step intensive sampling pharmacokinetic trial, we compared area under the concentration-time curve from 0 to 28 days (AUC0-28 days) of an active metabolite of amodiaquine, desethylamodiaquine, and treatment-emergent adverse events between antiretroviral therapy-naive HIV+ adults and those taking nevirapine and ritonavir-boosted lopinavir-based antiretroviral therapy. In step 1, malaria uninfected adults (n=6/arm) received half the standard adult treatment regimen of artesunate-amodiaquine. In step 2, another cohort (n=25/arm) received the full regimen. In step 1, there were no safety signals and significant differences in desethylamodiaquine AUC0-28 days among participants in the ritonavir-boosted lopinavir, nevirapine and antiretroviral therapy-naive arms. In step 2, compared with the antiretroviral therapy-naive arm, participants in the ritonavir-boosted lopinavir arm had 51% lower desethylamodiaquine AUC0-28 days, (geometric mean [95% CI]; 23,822 [17,458-32506] vs 48,617 [40,787-57,950] ng.hr/mL, p &lt; 0.001). No significant differences in AUC0-28 days were observed between nevirapine and antiretroviral therapy-naïve arms. Treatment-emergent transaminitis was higher in the nevirapine (20% [5/25]) than the antiretroviral therapy naïve (0.0% [0/25]) arm (risk difference 20% [95% CI:4.3-35.7] p=0.018). Ritonavir-boosted lopinavir antiretroviral regimen was associated with reduced desethylamodiaquine exposure which may compromise artesunate-amodiaquine's efficacy. Co-administration of nevirapine and artesunate-amodiaquine may be associated with hepatoxicity

Molecular markers for failure of sulfadoxine-pyrimethamine and chlorproguanil-dapsone treatment of Plasmodium falciparum malaria

Molecular assays for monitoring sulfadoxine-pyrimethamine-resistant Plasmodium falciparum have not been implemented because of the genetic and statistical complexity of the parasite mutations that confer resistance and their relation to treatment outcomes. This study analyzed pretreatment dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) genotypes and treatment outcomes in a double-blind, placebo-controlled trial of sulfadoxine-pyrimethamine and chlorproguanildapsone treatment for uncomplicated P. falciparum malaria. Multiple logistic regression was used to identify mutations that were predictive of treatment failure and to identify interactions and confounding factors. Infections caused by parasites with 3 DHFR mutations and 2 DHPS mutations (the "quintuple mutant") were associated with sulfadoxine-pyrimethamine treatment failure but not with chlorproguanil-dapsone treatment failure. The presence of a single DHFR mutation (Arg-59) with a single DHPS mutation (Glu-540) accurately predicted the presence of the quintuple mutant. If this model is validated in other populations, it will finally be possible to use molecular markers for surveillance of antifolate-resistant P. falciparum malaria in Africa