Efficacy of 400 mg Efavirenz Versus Standard 600 mg Dose in HIV/TB Co-infected Patients

Inclusion Criteria: * Subject or the subject's legal representative is willing and able to understand and provide signed and dated written informed consent prior to Screening * Adult subject (at least 18 years of age) * Naive to antiretroviral therapy (\<=14 days of prior therapy with any antiretroviral drug following a diagnosis of HIV-1 infection) * CD4+ cell count is \>= 50 cells/ cubic millimetre (mm\^3) at Screening * A female subject may be eligible to enter and participate in the study if she: is of non-childbearing potential defined as either postmenopausal (12 months of spontaneous amenorrhea and \>=45 years of age) or physically incapable of becoming pregnant or does not want to pregnancy * New diagnosis of TB (microbiology or molecular methods or clinical diagnosis) and started rifampicin based regimen for less no longer than 8 weeks at screening Exclusion Criteria: * Evidence of RIF resistance of Mycobacterium tuberculosis either by culture or validated nucleic acid amplification test * Concomitant disorders or conditions for which isoniazid, RIF, pyrazinamide, or ethambutol are contraindicated * Central nervous system TB * Women who are pregnant or breastfeeding * Subjects with moderate to severe hepatic impairment (Class B or C) as determined by Child-Pugh classification unstable liver disease * Anticipated need for hepatitis C virus (HCV) therapy during the study period * History or presence of allergy or intolerance to the study drugs or their components or drugs of their class * Subjects who, in the investigator's judgment, pose a significant suicidality risk. * Treatment with any of the following agents within 28 days of Screening: radiation therapy, cytotoxic chemotherapeutic agents, any immunomodulators that alter immune response * Exposure to an experimental drug or experimental vaccine within either 28 days, 5 half-lives of the test agent, or twice the duration of the biological effect of the test agent, whichever is longer, prior to the first dose of investigate drug * Any evidence of primary viral resistance to Nucleoside reverse transcriptase inhibitor (NRTIs), Non-nucleoside reverse transcriptase inhibitor (NNRTIs) based on the presence of any major resistance-associated mutation in the Screening result or, if known, any historical resistance test result. * Any acute laboratory abnormality at Screening, which, in the opinion of the investigator, would preclude the subject's participation in the study of an investigational compound.