Chonlaphat SukasemTim R. CresseyPattamawan PrapaithongYardpiroon TawonEkawat PasomsubChutatip SrichunrusamiThawinee JantararoungtongMarc LallementWasun ChantratitaDivision of Pharmacogenomics and Personalized MedicineMahidol UniversityChiang Mai UniversityHarvard School of Public HealthIRD Institut de Recherche pour le Developpement2018-06-112018-06-112012-12-01British Journal of Clinical Pharmacology. Vol.74, No.6 (2012), 1005-101213652125030652512-s2.0-84869010225https://repository.li.mahidol.ac.th/handle/123456789/14485Aims: To investigate the frequency of CYP2B6 polymorphisms and the influence of haplotype structure on plasma efavirenz concentrations in Thai adults with HIV-1 infection. Methods: Genotyping of nine single nucleotide polymorphisms (SNPs, c.64C > T, c.499C > G, c.516G > T, c.785A > G, c.1375A > G, c.1459C > T, g.3003T > C, g.18492C > T and g.21563C > T) of CYP2B6 were performed using real-time PCR-based allelic discrimination on blood samples from 52 HIV-infected adults who had received an efavirenz-based regimen. Plasma efavirenz concentrations were measured by high performance liquid chromatography. Results: The minor allele frequencies for c.64C > T, c.516G > T, c.785A > G, g.3003C > T, g.18492T > C and g.21563C > T were 0.087, 0.365, 0.413, 0.308 and 0.356, respectively. However, no variant alleles were identified for three SNPs (c.499 C > G, c.1375 A > G and c.1459 C > T). Efavirenz plasma concentrations were significantly associated with c.516G > T (P= 0.0095), c.785A > G (P= 0.0017), g.21563C > T (P= 0.0036) and g.18492C > T (P= 0.0011). The composite CYP2B6 of three SNPs (c.516G ≥ T, c.785A ≥ G and g.21563C ≥ T) genotypes were significantly associated with higher efavirenz concentrations. Conclusions: Our data indicate that the GAC-CYP2B6 haplotype is associated with higher plasma efavirenz concentrations in HIV-infected Thai adults. © 2012 The Authors. British Journal of Clinical Pharmacology © 2012 The British Pharmacological Society.Mahidol UniversityMedicinePharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1111/j.1365-2125.2012.04288.x