We do not think that the increase in efavirenz clearance following discontinuation of anti-TB therapy was due to increased age of the patients (i.e., a developmental effect), because CYP2B6 activity appears as early as the first day of life, and CYP2B6 levels and activity approach those of adults by 1 year of age (30). The gene discussed is CYP2B6; the disease is tuberculosis.