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

Mlotha, R, Waterhouse, David, Dzinjalamala, F, Ardrey, Alison, Molyneux, E, Davies, G R and Ward, S (2015) 'Pharmacokinetics of anti-TB drugs in Malawian children: reconsidering the role of ethambutol'. Journal of Antimicrobial Chemotherapy, Vol 70, Issue 6, pp. 1798-1803.

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Abstract

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.

Item Type: Article
Subjects: QV Pharmacology > Anti-Inflammatory Agents. Anti-Infective Agents. Antineoplastic Agents > QV 268 Antitubercular agents. Antitubercular antibiotics
QV Pharmacology > QV 38 Drug action.
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WF Respiratory System > Tuberculosis > WF 415 Tuberculosis in childhood
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Digital Object Identifer (DOI): https://doi.org/10.1093/jac/dkv039
Depositing User: Jessica Jones
Date Deposited: 27 Jan 2016 11:23
Last Modified: 06 Feb 2018 13:11
URI: http://archive.lstmed.ac.uk/id/eprint/5541

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