e45 (UGT) and is a substrate of P-glycoprotein (P-gp), coded by UGT and the ATP-binding cassette (ABCB1) genes respectively Methods: We assessed the effect of genetic variability in UGT1A and ABCB1 on moxifloxacin pharmacokinetics in South African tuberculosis patients. Genotypes for selected UGT1A and ABCB1 SNPS were determined using a TaqMan ® Genotyping OpenArray™, except for rs8175347 where a high resolution melt (HRM) analysis was used to measure TA repeats. A nonlinear mixed-effects model was used to describe moxifloxacin pharmacokinetics. Results: We determined the frequency of genetic variability in UGT1A and ABCB1 in 172 patients. Genotypes of UGT1A SNP's, rs8175347 and rs3755319 were significantly associated with changes in moxifloxacin pharmacokinetic parameters (clearance (CL) and bioavailability). Individuals with the AC or AA genotype for rs3755319 had on average 12.6% higher moxifloxacin clearance and lower AUC compared to individuals with the CC genotype (p = 0.021). TA repeats within the TATA box of the promoter region, showed donors that had TA 5/6 repeats within rs8175347 SNP had a significantly lower clearance and higher bioavailability associated with an approximately 32% increase in AUC compared to TA 6/6, 6/7 and 7/8 repeats (p= 0.001). Genotypes of the ABCB1 SNP rs2032582 were significantly associated with 40% reduced pre-hepatic bioavailability lower AUC in individuals with the CA genotype.