A 65-year-old HIV negative woman was affected by pulmonary tuberculosis. She underwent a partial gastrectomy for a gastric ulcer 15 years earlier. Her weight was 39 Kg; she was treated with standard anti TB therapy including isoniazid 250 mg daily, rifampin 600 mg daily, ethambutol 1000 mg daily and pyrazinamide 1000 mg daily, vitamin B6 300 mg daily. The drugs were administered intra venous (iv) in the first 15 days and oral subsequently (pyrazinamide and vitamin B6 were always administered orally). No other drugs were taken by this patient. We studied the plasmatic drugs concentration in the course of iv and oral therapy. Plasma samples were collected before the daily drug intake to measure Ctrough and after 2 hours and 5 hours to measure Cmax. The results of plasma concentrations, AUC0-24 during oral therapy are shown in the table. During iv therapy the measured AUC0-24 was very similar from the one reported in the course of oral treatment: isoniazid 26.70 hr*mg/L, rifampin 154.87 hr*mg/L, ethambutol 32.48 hr*mg/L. The patient obtained adequate clinical response.