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Antimicrobial Agents and Chemotherapy, March 2009, p. 863-868, Vol. 53, No. 3
0066-4804/09/$08.00+0 doi:10.1128/AAC.00899-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
CYP2B6 G516T Polymorphism but Not Rifampin Coadministration Influences Steady-State Pharmacokinetics of Efavirenz in Human Immunodeficiency Virus-Infected Patients in South India
Geetha Ramachandran,1
A. K. Hemanth Kumar,1
Sikhamani Rajasekaran,2
P. Kumar,1
K. Ramesh,1
S. Anitha,1
G. Narendran,1
Pradeep Menon,1
C. Gomathi,2 and
Soumya Swaminathan1*
Department of Clinical Research, Tuberculosis Research Centre (Indian Council of Medical Research), Chennai, India,1 Government Hospital of Thoracic Medicine, Tambaram, Chennai, India2
Received 8 July 2008/ Returned for modification 18 October 2008/ Accepted 27 December 2008
The dose of efavirenz during concomitant rifampin (RMP) administration is a matter of debate. We studied the influence of RMP coadministration on the steady-state pharmacokinetics of efavirenz in human immunodeficiency virus type 1 (HIV-1)-infected patients in South India. Fifty-seven HIV-tuberculosis (TB)-coinfected and 15 HIV-1-infected patients receiving combination antiretroviral therapy (CART) with an efavirenz (600 mg once daily)-containing regimen were recruited. HIV-TB-coinfected patients were receiving treatment with RMP-containing regimens. A complete pharmacokinetic study was conducted with 19 HIV-TB patients on two occasions (with and without RMP). Trough concentrations of efavirenz were measured in the remaining 38 patients during RMP coadministration. The 15 HIV-infected patients underwent complete pharmacokinetic sampling on one occasion. Plasma efavirenz was estimated by high-performance liquid chromatography, and genotyping of CYP2B6 G516T polymorphism was performed by sequencing. Peak and trough concentrations and exposure to efavirenz were significantly higher in TT than in GT and GG genotype patients (P < 0.001). Although RMP coadministration decreased the peak and trough concentrations and exposure to efavirenz by 17.8, 20.4, and 18.6%, respectively, the differences were not statistically significant. The trough concentration of efavirenz was subtherapeutic (less than 1.0 µg/ml) in 6 (8%) of 72 patients. In this South Indian population of HIV-infected patients, CYP2B6 G516T polymorphism but not RMP coadministration significantly influenced the pharmacokinetics of efavirenz; patients with the TT genotype had very high blood levels of efavirenz. While a small proportion of patients had subtherapeutic efavirenz levels, the clinical implications are uncertain, as all had good immunological responses to CART.
* Corresponding author. Mailing address: Department of Clinical Research, Tuberculosis Research Centre, Mayor V. R. Ramanathan Road, Chetput, Chennai-600 031, India. Phone: 91-44-28369586. Fax: 91-44-28362528. E-mail: doctorsoumya{at}yahoo.com
Published ahead of print on 5 January 2009.
Antimicrobial Agents and Chemotherapy, March 2009, p. 863-868, Vol. 53, No. 3
0066-4804/09/$08.00+0 doi:10.1128/AAC.00899-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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