Treatment of isoniazid-resistant tuberculosis with isoniazid, rifampin, ethambutol, and pyrazinamide for 6 months.

SETTING

In 1992 the Seattle-King County Department of Public Health Tuberculosis Clinic began to treat patients with isoniazid-resistant tuberculosis with a regimen of isoniazid, rifampin, pyrazinamide, and ethambutol daily for 6 months.

OBJECTIVE

To conduct a review of clinical and bacteriological outcomes of treatment for patients who received the four-drug, 6-month regimen for isoniazid-resistant tuberculosis.

DESIGN

A retrospective review of medical records of TB cases meeting the study criteria, a Mycobacterium tuberculosis isolate resistant to isoniazid, and intent to treat with a 6-month course of isoniazid, rifampin, pyrazinamide, and ethambutol.

RESULTS

Through December 1999, 44 consecutive patients with isoniazid-resistant, rifampin-susceptible tuberculosis were started on the four-drug, 6-month daily regimen. Among 42 patients followed until completion of therapy, three required changes in the regimen due to side effects. There was one case of drug-induced hepatotoxicity. Among 39 patients with pulmonary involvement, 37 converted sputum cultures from positive to negative within 2 months of starting treatment. There were no treatment failures. On passive follow-up of at least 2 years on all patients, two patients relapsed. The single patient with bacteriological relapse did not develop further drug resistance.

CONCLUSION

The regimen of isoniazid, rifampin, pyrazinamide, and ethambutol given daily for 6 months produced successful outcomes when used in a public health tuberculosis clinic as routine therapy for isoniazid-resistant tuberculosis.