Rifampicin and CYP2B6 Genotype Influence efavirenz Autoinduction and hence Plasma Exposure

Materials and methods This was a prospective comparative study in which treatment naive Tanzanian HIV patients with (arm2, n=54) or without TB co-infection (arm1, n=128) were recruited and followed up. All patients were initiated on EFV based HIV therapy and in arm2 TB therapy was initiated 4 weeks before. CYP2B6 was genotyped to identify *1 or *6 allele. Plasma EFV and 8-hydroxy efavirenz concentrations were determined at week4 and 16 by LC-MS. One way and two ways ANOVA were used for groups and groups repeated measures comparisons of EFV levels respectively. Univariate and multivariate logistic regression was used to assess risk factors for having plasma levels below 1µg/mL or above 4µg/mL