title: CYP2B6 G516T polymorphism but not rifampin coadministration influences steady-state pharmacokinetics of efavirenz in human immunodeficiency virus-infected patients in South India.
abstract: 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 microg/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.
authors.affiliation: Department of Clinical Research, Tuberculosis Research Centre, Chetput, Chennai, India.
authors.forename: Geetha
authors.initials: G
authors.lastname: Ramachandran
authors.forename: A K
authors.initials: AK
authors.lastname: Hemanth Kumar
authors.forename: Sikhamani
authors.initials: S
authors.lastname: Rajasekaran
authors.forename: P
authors.initials: P
authors.lastname: Kumar
authors.forename: K
authors.initials: K
authors.lastname: Ramesh
authors.forename: S
authors.initials: S
authors.lastname: Anitha
authors.forename: G
authors.initials: G
authors.lastname: Narendran
authors.forename: Pradeep
authors.initials: P
authors.lastname: Menon
authors.forename: C
authors.initials: C
authors.lastname: Gomathi
authors.forename: Soumya
authors.initials: S
authors.lastname: Swaminathan
mesh_terms: D000328:Adult; D000480:Alkynes; D019380:Anti-HIV Agents / Q000493:pharmacokinetics*; D000904:Antibiotics, Antitubercular / Q000627:therapeutic use; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D048588:Benzoxazines / Q000493:pharmacokinetics*; D003521:Cyclopropanes; D065702:Cytochrome P-450 CYP2B6; D004359:Drug Therapy, Combination; D005260:Female; D005843:Geography; D015658:HIV Infections / Q000150:complications / Q000188:drug therapy* / Q000235:genetics; D015497:HIV-1 / Q000235:genetics; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics*; D011110:Polymorphism, Genetic; D012293:Rifampin / Q000009:adverse effects / Q000627:therapeutic use*; D014376:Tuberculosis / Q000150:complications / Q000188:drug therapy
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D000904:Antibiotics, Antitubercular; D048588:Benzoxazines; D003521:Cyclopropanes; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; D065702:Cytochrome P-450 CYP2B6; D010089:Oxidoreductases, N-Demethylating; C098320:efavirenz; D012293:Rifampin