title: A rapid and sensitive HPLC-MS method for the detection of plasma and cellular rifampicin.
abstract: Rifampicin is active against both intracellular and extracellular Mycobacterium tuberculosis. The ability to measure rifampicin drug concentrations in both plasma and in cells may be useful in evaluating the suitability of dosage regimens for populations and individuals. Here a novel simple, precise and accurate method for the quantification of rifampicin in both cells and plasma is reported. Sample proteins were precipitated with acetonitrile containing the internal standard and then diluted with water. Aliquots of supernatant were then injected into the HPLC-MS system for chromatographic separation and detection. Rifampicin calibration curves encompassed concentrations from 100 to 12,800 ng/mL. Intra- and inter-assay precision and accuracy were determined using low, medium and high concentration quality control samples and was found to be within 10% in all cases. Rifampicin concentrations were found to be unaffected by freeze-thaw cycles, but were significantly affected by heat-inactivation (58 degrees C, 40 min). This assay was successfully utilised to determine the pharmacokinetic profile of rifampicin in plasma and peripheral blood mononuclear cells (PBMC) in 8 tuberculosis patients receiving rifampicin over an 8h period.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Liverpool, 70 Pembroke Place, Liverpool, UK. rchart@liverpool.ac.uk
authors.forename: Ruben C
authors.initials: RC
authors.lastname: Hartkoorn
authors.forename: Saye
authors.initials: S
authors.lastname: Khoo
authors.forename: David J
authors.initials: DJ
authors.lastname: Back
authors.forename: John F
authors.initials: JF
authors.lastname: Tjia
authors.forename: Catriona J
authors.initials: CJ
authors.lastname: Waitt
authors.forename: Masautso
authors.initials: M
authors.lastname: Chaponda
authors.forename: Geraint
authors.initials: G
authors.lastname: Davies
authors.forename: Alison
authors.initials: A
authors.lastname: Ardrey
authors.forename: Samantha
authors.initials: S
authors.lastname: Ashleigh
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Ward
mesh_terms: D000284:Administration, Oral; D000995:Antitubercular Agents / Q000097:blood* / Q000493:pharmacokinetics; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods; D004355:Drug Stability; D005260:Female; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000737:chemistry*; D008297:Male; D013058:Mass Spectrometry / Q000295:instrumentation* / Q000379:methods; D012015:Reference Standards; D015203:Reproducibility of Results; D012293:Rifampin / Q000097:blood* / Q000493:pharmacokinetics; D012294:Rifamycins / Q000592:standards; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000097:blood* / Q000188:drug therapy*
chemical_list: D000995:Antitubercular Agents; D012294:Rifamycins; C023808:rifamycin SV; D012293:Rifampin