title: Simultaneous quantification of isoniazid, rifampicin, ethambutol and pyrazinamide by liquid chromatography/tandem mass spectrometry.
abstract: A remediable cause of poor treatment response in drug-susceptible tuberculosis (TB) patients may be low plasma levels of one or more of the first-line anti-TB drugs. The aim of this work was to develop an accurate and precise LC-MS/MS method for simultaneous quantification of all four first-line anti-TB drugs in plasma suitable for therapeutic drug monitoring (TDM). To adjust for degradation and losses during sample preparation, isotopically labeled compounds were used as internal standards. Plasma samples spiked with internal standards were extracted using protein precipitation with methanol and acetonitrile. Simultaneous separation of all four drugs was accomplished with a Chromolith Reversed-Phase column and mobile phases consisting of water, methanol, ammonium acetate and formic acid with subsequent mass spectrometric quantification. The linear range of the calibration curve for isoniazid was 0.5-10 mg/L, for rifampicin 0.75-30 mg/L, for ethambutol 0.25-10 mg/L and for pyrazinamide 4-80 mg/L. The lower limit of quantification was 0.5 mg/L, 0.75 mg/L, 0.25 mg/L and 4.0 mg/L, respectively. Precision estimated by the coefficient of variation was <15% for all four drugs. The LC-MS/MS method can readily be used for simultaneous quantification of first-line anti-TB drugs in plasma and is well suited for TDM.
authors.affiliation: International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark. j.prahl@dadlnet.dk.
authors.forename: Julie B
authors.initials: JB
authors.lastname: Prahl
authors.affiliation: Department of Congenital Diseases, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Marika
authors.initials: M
authors.lastname: Lundqvist
authors.affiliation: Department of Autoimmunology and Biomarkers, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Justyna M C
authors.initials: JM
authors.lastname: Bahl
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.
authors.forename: Isik S
authors.initials: IS
authors.lastname: Johansen
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen Ø, Denmark.
authors.forename: Åse B
authors.initials: ÅB
authors.lastname: Andersen
authors.affiliation: Department of Clinical Microbiology, Copenhagen University Hospital Rigshospitalet, Copenhagen Ø, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Frimodt-Møller
authors.affiliation: Department of Congenital Diseases, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Arieh S
authors.initials: AS
authors.lastname: Cohen
mesh_terms: D000995:Antitubercular Agents / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods; D004977:Ethambutol / Q000032:analysis*; D006801:Humans; D007538:Isoniazid / Q000032:analysis*; D010949:Plasma / Q000737:chemistry; D011718:Pyrazinamide / Q000032:analysis*; D012293:Rifampin / Q000032:analysis*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000995:Antitubercular Agents; D011718:Pyrazinamide; D004977:Ethambutol; D007538:Isoniazid; D012293:Rifampin
keywords: Isoniazid; LC-MS/MS; ethambutol; pyrazinamide; rifampicin