Fig 2.

Relative abundances of INH metabolites in the urine of patients undergoing anti-TB therapy. (A) N-Acetyl isoniazid, isonicotinyl glycine, and a product with an [M+H]⁺ molecular ion of 228.0768 m/z were detected by LC-MS in the urine of eight patients at 2 weeks (W2) and 8 weeks (W8) after the start of therapy. (B) The product with an [M+H]⁺ molecular ion of 228.0768 m/z was not present in patients' urine prior to the start of anti-TB therapy (day 0) but could be detected at significantly above background level after 2 and 6 months of therapy. Each closed circle represents one patient. All eight patients were infected with INH-sensitive organisms, and sputum cultures from these patients after week 8 of therapy were negative for M. tuberculosis.