Antiretroviral therapy substantially reduces mortality rate among HIV/TB-coinfected patients. Initiation of ART within 6 months of TB diagnosis is associated with greater survival.

Antiretroviral therapy regimens containing efavirenz (600 mg per day) were less compromised by concomitant use of rifampicin than were those that contained nevirapine (400 mg per day) in patients with concurrent HIV-1 infection and TB. Low drug exposure and low body weight are important predictive factors for treatment failure.

In middle-income countries where ART is initiated at CD4 count of <350 cells per cubic millimeter, immediate initiation of ART in HIV-infected patients with active TB was not associated with survival advantage when compared to initiation of ART at 12 weeks.

bComprehensive information on the effects of cytochrome P450 2B6 (CYP2B6) polymorphisms, clinical factors, and drug-drug interactions on efavirenz concentrations in HIV/tuberculosis-coinfected (HIV/TB) patients is unavailable. A total of 139 HIV/TB adults, 101 of whom received a rifampin-containing anti-TB regimen, were prospectively enrolled to receive efavirenz (600 mg)/ tenofovir/lamivudine. Nine single nucleotide polymorphisms (SNPs) within CYP2B6 were genotyped. Plasma efavirenz concentrations were measured at 12 weeks. The median (interquartile range [IQR]) efavirenz concentration was 2.3 (1.4 to 3.9) mg/liter. The SNPs (frequencies of heterozygous and homozygous mutants) were 64C>T (10% and 1%), 499C>G (0% and 0%), 516G>T (47% and 8%), 785A>G (54% and 10%), 1375A>G (0% and 0%), 1459C>T (3% and 0%), 3003C>T (44% and 27%), 18492T>C (39% and 6%), and 21563C>T (57% and 5%). The four most frequent CYP2B6 haplotypes identified were *1/*6 (41%), *1/*1 (35%), *1/*2 (7%), and *6/*6 (7%). The heterozygous/homozygous mutation associated with low efavirenz concentrations was 18492T>C (P < 0.001), and those associated with high efavirenz concentrations were 516G>T, 785A>G, and 21563C>T (all P < 0.05). Haplotype *1/*1 was associated with low efavirenz concentrations, and *6/*6, *1/*6, and *5/6 were associated with high efavirenz concentrations. As shown by multivariate analysis, low efavirenz concentrations were significantly associated with the *1/*1 haplotype (beta ‫؍‬ ؊1.084, P ‫؍‬ 0.027) and high body weight (beta ‫؍‬ ؊0.076, P ‫؍‬ 0.002). In conclusion, pharmacogenetic markers of CYP2B6 have the greatest impact with respect to inducing low plasma efavirenz concentrations in HIV/TB Thai patients.