Aim: Little is known about pyridoxine nutriture of children treated with isoniazid (INH) regimens. This study documents plasma pyridoxal 5′-phosphate (PLP) concentrations in children, HIV-infected and HIV-uninfected, receiving INH regimens. Methods: Children from the Western Cape of South Africa hospitalized for tuberculosis (TB) management were studied. Plasma PLP concentrations were determined on enrolment, 1-month after commencing TB treatment, and again after 4-month’s treatment. The children received a supplement meeting pyridoxine requirements. Results: Nineteen HIV-infected and 33 HIV-uninfected children received INH (dosage range 4–20 mg/kg) daily. Mean PLP plasma concentrations on enrolment were 8.32 (SD 6.75) ng/mL and 11.28 (SD 3.02) ng/mL in HIV-infected and HIV-uninfected children, respectively (p = 0.11) and after 4-month’s treatment 6.75 (SD 2.71) ng/mL and 14.76 (SD 7.96) ng/mL (p
