In response to letter from Sahu, we wish to inform that: (a)
the group extensively deliberated about appropriate doses
for anti-TB drugs to be recommended for our country based on
available evidence and concluded that the earlier
recommended dosages needed revision. The current dosages
were arrived after looking into various available
pharmacokinetic data and evidence within and outside the
country (published and unpublished data from studies at
AIIMS and NIRT). The group arrived at these recommendations
as a consensus, while keeping in mind the absolute need for
adequate serum levels and also the possible risk of
cumulative hepatotoxicity; (b) the group recommends
the total duration of ATT in intracranial TB including TB
Meningitis should be 9-12 months depending upon the clinical
progress on treatment. This is in consonance with available
evidence and experience; and (c) among retreatment
cases, the INH resistance is significant but not absolute,
hence a third drug ethambutol, is added to in the
continuation phase (RHE). There is no scientific basis or
evidence for including pyrazinamide instead of ethambutol in
the continuation phase. Pyrazinamide works best when there
is active inflammation and in acidic pH, hence its benefit
may not be seen during the continuation phase [1].
Furthermore, addition of Ethambutol not only helps in
preventing emergence of drug resistance [2] but also would
minimize the potential risk of hepato-toxicity with
prolonged use of the suggested three hepatotoxic drugs
(RHZ).
Reference
1. Snider DE Jr. Controlled clinical
trial of four 6-month regimens of chemotherapy for pulmonary
tuberculosis. Second East Africal/British Medical Research
Council Study. Am Rev Respir Dis. 1976; 114:471-75.
2. Wallace F. The chemotherapy of pulmonary tuberculosis:
a review. Chest. 1979;76:785-96 .
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