Effect of initial isoniazid resistance on response to chemotherapy of tuberculosis: A review of clinical trials.

This study evaluated seventeen clinical trials of short-course chemotherapy of tuberculosis and assessed the influence of initial resistance to isoniazed on the response to therapy. High failure rates were observed for the non-rifampicin-containing regimens. When rifampicin was included, there was a very good response among patients suffering from sensitive and resistant strains. Regimens that included both rifampicin and pyrazinamide yielded the best results, with low failure rates observed for sensitive and resistant patients. The addition of streptomycin and ethambutol to these regimens did not improve the response in patients with isoniazid-resistant bacilli. Prolonged therapy generally yielded a better response; however, in rifampicin-containing regimens, the use of pyrazinamide for more than two months did not influence the outcome of therapy. In patients with isoniazid-resistant strains, 4- and 6-month regimens containing rifampicin and pyrazinamide both yielded low failure rates. Initial isoniazid resistance had very little impact on the response to such regimens when therapy was carried out for 6 months.