Abstract

For the effective treatment of tuberculosis with first-line anti-tubercular drugs, drug concentrations need to be measured at the site of infection to determine drug exposure. To enable the measurement of the anti-tuberculosis drugs isoniazid and pyrazinamide in the nervous system of patients with tuberculous meningitis, an analytical method was developed and validated for the quantification of these drugs in human cerebrospinal fluid. Samples were prepared by solid phase extraction using Strata-X polymeric extraction plates. The analytes were separated by high-performance liquid chromatography on an Atlantis T3, 100 A, 3 µm, 2.1 mm × 100 mm analytical column with gradient elution, employing a mobile phase that consisted of acetonitrile-methanol-formic acid (50:50:0.1, v/v/v), at a flowrate of 0.25 mL/min. The total run time was 4.5 minutes, and the average retention times of isoniazid and pyrazinamide were 1.1 and 1.3 min, respectively. The analytes and their respective deuterated internal standards were detected on a Sciex API4000 triple quadrupole mass spectrometer applying positive electrospray ionization with multiple reaction monitoring as the detection mode. The method was validated according to the FDA and EMA guidelines. The method was demonstrated to be accurate, reproducible, and robust, showing the necessary sensitivity and specificity for the quantification of isoniazid and pyrazinamide in cerebrospinal fluid. The method was successfully applied to analyze clinical samples from the LASER-TBM and TBM-KIDS clinical studies.