Optimal antituberculosis therapy is essential for favorable clinical outcomes. Peak plasma concentrations of first-line antituberculosis drugs in infants with living HIV receiving WHO-recommended dosing were low compared with reference values for adults, supporting studies on increased doses of first-line TB drugs in infants. Key words. HRZE; Tuberculosis; HIV; pharmacokinetics; infants. INTRODUCTION Tuberculosis (TB) is a leading cause of death in children living with HIV. Of the 214 000 TB deaths among people living with HIV in 2021, children accounted for 10% [1]. Infants are at risk of developing severe forms of TB when compared with older children [1, 2]. Optimal TB treatment is crucial to avert TB-associated mortality in infants with HIV