Determination and pharmacokinetic profile of pyrazinamide in rat blood, brain and bile using microdialysis coupled with high-performance liquid chromatography and verified by tandem mass spectrometry

This study demonstrates a rapid and sensitive method for the concurrent determination of unbound pyrazinamide in rat blood, brain and bile using microdialysis coupled with high-performance liquid chromatography (HPLC) for further pharmacokinetic study. Microdialysis probes were simultaneously inserted into the jugular vein toward right atrium, the striatum of brain and the bile duct of male Sprague–Dawley rats for biological fluid sampling after the administration of pyrazinamide (10, 30 or 100 mg kg^-1) through the femoral vein. Pyrazinamide was separated from various dialysates using a reversed-phase C18 column maintained at ambient temperature. The mobile phase consisted of acetonitrile -10 mM monosodium phosphate (10:90, v/v) for blood and brain dialysates, and methanol–10 mM monosodium phosphate (10:90, v/v) for bile dialysate. The UV detector wavelength was set at 268 nm and the detection limit of pyrazinamide was 100 ng ml^-1. The presence of pyrazinamide in biological fluid samples was verified with liquid chromatography–triple quadrupole tandem mass spectrometry using electrospray ionization. The results suggest that microdialysis sampling followed by LC separation with UV detection is a viable approach for the measurement of free pyrazinamide in rat blood, brain and bile. The decline of unbound pyrazinamide in the blood, brain striatum and bile fluid indicates that there was rapid exchange and equilibration between the compartments of the peripheral and central nervous systems. In addition, the results demonstrate that pyrazinamide was able to penetrate the blood–brain barrier and undergo hepatobiliary excretion.