Efficacy of the 6-month thrice-weekly regimen in the treatment of new sputum smear-positive pulmonary tuberculosis under clinical trial conditions.

Background. Under the Revised National Tuberculosis Control Programme of India, patients with new smear-positive pulmonary tuberculosis are treated with a thrice-weekly regimen of antitubercular drugs (2H3R3Z3E3/4H3R3 [H isoniazid, R rifampicin, Z pyrazinamide and E ethambutol]) for 6 months. We conducted a retrospective analysis of the efficacy and tolerability of this regimen under clinical trial conditions in HIV-negative patients with newly diagnosed smear-positive pulmonary tuberculosis. Methods. We retrospectively analysed the data on patients assigned to the control regimen (2H3R3Z3E3/4H3R3) in two clinical trials during 2001–06 at the National Institute for Research in Tuberculosis, Chennai, India. Results. Of the 268 patients treated with this regimen, data for efficacy analysis were available for 249. At the end of treatment, of 249 patients, 238 (96%) had a favourable status. Treatment failure occurred in the remaining 11: 7 in whom the organisms were initially drug-susceptible and 4 with initial drug resistance. Of the 238 patients who had a favourable status at the end of treatment, 14 (6%) had recurrence of tuberculosis during the following 24 months. In the intention-to-treat analysis, 245 (94%) of 262 patients had a favourable status at the end of treatment. Of the 28 patients with initial drug resistance, 24 (86%) had a favourable outcome. Only 4 of these 24 patients were found to have recurrence of tuberculosis in 2 years of follow-up. Among the 221 patients initially infected with drug-susceptible organisms, drug resistance did not develop in any of the 7 patients in whom the treatment failed or the 10 who had recurrence of tuberculosis. Further, 5 of the 7 patients in whom the treatment failed continued to excrete drug-susceptible bacilli at 6 months. Adverse drug reactions were observed in 38 (14%) of the 262 patients. Only 3 (1.1%) needed a modification in the treatment. Conclusion. This thrice-weekly 6-month regimen of antitubercular drugs, when administered under full supervision, is associated with a high rate of favourable treatment outcomes in HIV-negative patients with newly diagnosed sputum smearpositive pulmonary tuberculosis. There are few adverse drug reactions in these patients.

Early bactericidal action of pulsed exposure to rifampicin, ethambutol, isoniazid & pyrazinamide in pulmonary tuberculosis patients.

The bactericidal action of two therapeutic regimens on Mycobacterium tuberculosis was assessed by viable counts in serial sputum samples in 49 pulmonary tuberculosis patients being treated with rifampicin (R), ethambutol (Emb), isoniazid (I) and pyrazinamide (Z) together in a single dose thrice weekly (REmbIZ3) or with REmb and IZ on alternate days (REmb3IZ3alt). In both groups of patients, there was a significant reduction (P < or = 0.02) in the colony forming units (cfu) of M. tuberculosis per ml of sputum during the first two days of treatment itself. This early bactericidal action (EBA) as well as the reduction in counts during the subsequent days of treatment were similar (P > 0.2) for both REmbIZ3 and REmb3IZ3alt regimens indicating that splitting up REmbIZ into REmb on one day and IZ on the next day in short course chemotherapy (SCC) regimens may not affect the bactericidal action of the regimens.