Bacterial Factors and Relapse after Tuberculosis Therapy

Abstract

To the Editor: Colangeli et al. (Aug. 30 issue)1 report that higher minimum inhibitory concentration (MIC) values of rifampin and isoniazid were associated with a greater risk of treatment failure and relapse of tuberculosis than lower MIC values. We agree that critical concentrations may not be appropriate for all patients. Standardized dosing is also not appropriate for all patients.2 Most antituberculosis drugs have concentration-dependent activity (expressed as the ratio of the serum free-drug area under the concentration versus time curve [fAUC] to the MIC). Access to sites of infection is difficult, and plasma concentrations serve as practical surrogates. The ratio . . .