title: Determination of lopinavir cerebral spinal fluid and plasma ultrafiltrate concentrations by liquid chromatography coupled to tandem mass spectrometry.
abstract: A method for the determination of lopinavir (LPV) concentrations in cerebral spinal fluid (CSF) and plasma ultrafiltrate (UF) was developed and validated to analyze clinical specimens from patients receiving antiretroviral treatment with lopinavir/ritonavir. The CSF (400 microL sample volume) final calibration range for LPV was 0.313-25.0 ng/mL. The final calibration range for UF (50 microL sample volume) was 1.25-100 ng/mL. The samples were prepared using liquid-liquid extraction, concentrated, and analyzed using a reversed phase isocratic separation. Detection was achieved in positive mixed reaction monitoring mode on a triple quadrupole mass spectrometer. Isolation of LPV through chromatographic separation and proper selection of calibration matrix were important factors in achieving accurate results. Plasma UF was found to be an equivalent calibration matrix to CSF whereas plasma matrix produced a positive bias in samples with unknown concentrations. Artificial CSF media prepared chemically were biased and less superior than UF. Sources of plasma for the UF did not affect accuracy. Several CSF sources were tested for specificity of the method and LPV concentrations were accurately produced with atmospheric pressure chemical ionization source producing more accurate results than the electrospray source. The method successfully measured LPV concentrations in CSF that were previously undetectable by HPLC as well as UF from protein binding studies.
authors.affiliation: Department of Pharmacy Practice, University at Buffalo, NY 14260, United States. rda@buffalo.edu
authors.forename: Robin
authors.initials: R
authors.lastname: DiFrancesco
authors.forename: Robert
authors.initials: R
authors.lastname: DiCenzo
authors.forename: Glorimar
authors.initials: G
authors.lastname: Vicente
authors.forename: Julie
authors.initials: J
authors.lastname: Donnelly
authors.forename: Troy M
authors.initials: TM
authors.lastname: Martin
authors.forename: Luis A
authors.initials: LA
authors.lastname: Colon
authors.forename: Giovanni
authors.initials: G
authors.lastname: Schifito
authors.forename: Gene D
authors.initials: GD
authors.lastname: Morse
mesh_terms: D019380:Anti-HIV Agents / Q000097:blood* / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000302:isolation & purification; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D004355:Drug Stability; D005615:Freezing; D006801:Humans; D061466:Lopinavir; D015394:Molecular Structure; D011744:Pyrimidinones / Q000097:blood* / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000302:isolation & purification; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013997:Time Factors
chemical_list: D019380:Anti-HIV Agents; D011744:Pyrimidinones; D061466:Lopinavir