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Home >> Publications >> Effects of rifampin-based antituberculosis therapy on plasma efavirenz concentrations in children vary by CYP2B6 genotype.

Publication

Author(s):

McIlleron HM, Schomaker M, Ren Y, Sinxadi P, Nuttall JJ, Gous H, Moultrie H, Eley B, Merry C, Smith P, Haas DW, Maartens G.

Pub Title:

Effects of rifampin-based antituberculosis therapy on plasma efavirenz concentrations in children vary by CYP2B6 genotype.

Pub Date:

Jul 31 2013

Pub Region(s):

Southern Africa

Journal Issue:

27(12)

Page Number:
1933-1940

Journal:

Title: 
AIDS
Link: 
http://bit.ly/HUYav7

PubMed: 24180002
Pub PDF: PDF icon 24180002.pdf

Abstract
OBJECTIVES
: An efavirenz-based antiretroviral therapy (ART) regimen is preferred for children more than 3 years of age with tuberculosis. However, rifampin, a key component of antituberculosis therapy, induces CYP2B6. An increased dose of efavirenz is recommended in adults weighing more than 50 kg who require rifampin, but there is scant information in children being treated for tuberculosis.

DESIGN: Plasma efavirenz concentrations were compared in 40 children during concomitant treatment for tuberculosis and HIV-1, after stopping rifampicin, and in a control group of children without tuberculosis. Associations with antituberculosis treatment, metabolizer genotype (based on CYP2B6 516G→T, 983T→C, and 15582C→T), weight, and time after dose were evaluated.

RESULTS: Compared to children with extensive metabolizer genotypes, efavirenz concentrations were increased 1.42-fold (95% confidence interval, CI 0.94–2.15) and 2.85-fold (95% CI 1.80–4.52) in children with intermediate and slow metabolizer genotypes, respectively. Concomitant antituberculosis treatment increased efavirenz concentrations 1.49-fold (95% CI 1.10–2.01) in children with slow metabolizer genotypes, but did not affect efavirenz concentrations in extensive or intermediate metabolizer genotypes. After adjustment for dose/kg, each kilogram of weight was associated with a 2.8% (95% CI 0.9–4.7) decrease in efavirenz concentrations. Despite higher milligram per kilogram doses, a higher proportion of children in the lowest weight band (10–13.9 kg) had efavirenz concentrations less than 1.0 mg/l than larger children.

CONCLUSION: Antituberculosis treatment was not associated with reduced efavirenz concentrations in children, which does not support increased efavirenz doses. Children with slow metabolizer genotype have increased efavirenz concentrations during antituberculosis treatment, likely due to isoniazid inhibiting enzymes involved in accessory metabolic pathways for efavirenz.

 

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Citation:

McIlleron HM, Schomaker M, Ren Y, Sinxadi P, Nuttall JJ, Gous H, Moultrie H, Eley B, Merry C, Smith P, Haas DW, Maartens G. Effects of rifampin-based antituberculosis therapy on plasma efavirenz concentrations in children vary by CYP2B6 genotype. AIDS. 2013 Jul 31;27(12):1933-40. PubMed PMID: 24180002.