A Lower Dose of Efavirenz Can Be Coadministered With Rifampicin and Isoniazid in Tuberculosis Patients

To the Editor—The ENCORE-1 study demonstrated noninferiority of efavirenz 400 mg once daily (EFV400) when compared with the standard dose (EFV600) [1]. Based on these data, the World Health Organization (WHO) recommends EFV400 as an alternative first-line antiretroviral drug but restricts its use to nonpregnant patients and patients without tuberculosis (TB) [2]. However, a recently published study in United Kingdom human immunodeficiency virus (HIV)-positive patients without TB found EFV concentrations to be adequate when EFV400 was coadministered with rifampicin and isoniazid (RH) [3]. To confirm these results in a TB-infected population, we conducted an open label, nonrandomized, pharmacokinetic study in HIV/TB coinfected patients in Uganda