As an effective regimen for isoniazid (INH)-resistant pulmonary tuberculosis, several treatment regimens have been recommended by many experts. In Korea, a standard regimen has not been established for INH-resistant tuberculosis, and the treatment by individual physicians has been performed on an empirical bases. The purpose of the present study was to retrospectively describe the treatment characteristics and evaluate the treatment outcomes of patients with INH-resistant tuberculosis.

Sixty of 69 patients reported to have INH-resistant tuberculosis from 1994 to 2001 were retrospectively analyzed. Exclusion criteria included: death from other causes, with the exceptions of tuberculosis and incomplete treatment, including a patient's transfer-out.

A previous tuberculosis history was found in 28 (46.7%) patients. The sputum smear for acid-fast bacilli was positive in 44 (73.3%) patients, and 30 (50.0%) had cavitary disease. Streptomycin resistance coexisted in 25.0% of isolates. INH was to be prescribed continuously, even after INH resistance was reported, in 86.0% of patients. The treatment regimens were diverse between the patients according to drug regimen composition and treatment duration. The most frequent prescribed regimen included rifampin, ethambutol and pyrazinamide, with and without INH, for the full 12-month term of treatment. Treatment failure occurred in 13 (21.7%) patients. Cavitary disease (p=0.005) and a treatment regimen with second-line drugs, excluding rifampin (p=0.015), were associated with treatment failure. One patient experienced a relapse.

Standardized treatment guidelines will be needed in Korea to improve the treatment efficacy for INH-resistant tuberculosis.