Background: Isoniazid-resistant tuberculosis (INHr-TB)
can be treated successfully with several treatment regimens. However,
the optimal regimen and duration are unclear.
objective: To analyze the efficacy of treatment regimens used for
INHr-TB in the southeastern Texas region.
Retrospective cohort study.
facilities reporting tuberculosis (TB) patients in the Houston and
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.