Treatment of isoniazid-resistant tuberculosis in southeastern Texas

Background: Isoniazid-resistant tuberculosis (INHr-TB) can be treated successfully with several treatment regimens, However, the optimal regimen and duration are unclear, Study objective: To analyze the efficacy of treatment regimens used for INHr-TB in the southeastern Texas region. Design: Retrospective cohort study, Setting: Health-care facilities reporting tuberculosis (TB) patients in the Houston and Tyler areas. Subjects: All patients reported to have INHr-TB from 1991 to 1998, Exclusion criteria included poor compliance, additional first-line drug-resistance (except aminoglycosides), and death before completion of 1 month of treatment. Measurements and results: Main treatment outcomes were treatment failure, relapse, and TB-related death. Fifty-three of 83 patients were included in the study; aminoglycoside resistance coexisted in 37.5% of isolates, Seven types of treatment regimens were identified. Eighteen patients (34%) received rifampin, pyrazinamide, and ethambutol thrice weekly for 9 months. Four patients (7.5%) had a total effective treatment duration of < 9 months. Thirty patients (56.6%) and 16 patients (30.2%) received thrice-daily and daily treatment regimens, respectively, Forty-nine patients achieved sputum conversion, Treatment failure and death occurred in one patient (1.9%), Three patients (5.7%) experienced relapses. There was a significant difference in total effective treatment time between patients with and without relapses (8.3 +/- 1.1 months vs 11.1 +/- 2.1 months; p < 0.02), Twice-weekly treatment regimens were associated with relapse (p = 0.05), Conclusions: Several treatment regimens were prescribed for INHr-TB in southeastern Texas. INHr-TB treatment durations were > 7 months, and treatment regimen efficacy was adequate. Twice-weekly treatment was associated with relapse, whereas thrice-weekly and daily treatments performed similarly, A prospective study with different treatment durations is needed to determine the optimal treatment regimen for patients with INHr-TB.