Therapeutic Drug Monitoring-how to tackle non-responsive drug sensitive tuberculosis

Therapeutic Drug Monitoring (TDM) helps in optimizing the dose which maximizes the therapeutic benefit and minimizes the toxicity. In pulmonary and extrapulmonary tuberculosis (PTB/EPTB), it allows the physician to take actions timely for antitubercular treatment (ATT) regimen, required in patients who are responding slowly to the treatment. Early interventions may prevent drug resistance development in such patients.

To see the effect of Therapeutic Drug Monitoring in Non responding Drug sensitive TB.

A retrospective study was conducted, wherein 8 Cases of TB, who underwent TDM, were studied. The dose of ATT was according to weight band and drug sensitivity testing was already done.

TDM was done in 8 cases of TB proved as PTB (12.5%, n = 1) and EPTB (87.5%, n = 7) by microbiological testing via AFB smear (12.5%, n = 1) and NAAT (87.5%, n = 7) and were not responding to conventional antitubercular regimen. Serum Rifampicin and Isoniazid levels were checked in 100% (n = 8) and 75% (n = 6) patients respectively. Serum Rifampicin level was reduced in 100% patients and Serum Isoniazid level was reduced in 66.6% (n = 4) and normal in 33.34% (n = 2) patients. Normal Serum concentration was achieved after dose adjustment in patients with low serum level of both drugs. Patients were monitored for adverse drug reactions (ADR) including hepatotoxicity. No patient showed ADR after increasing the dose.

We conclude that poor or no response to ATT makes the biased physician conclude the diagnosis as drug resistant TB. Therefore, it is important to look for another aspect for serum drug levels, hence TDM.