title: A rapid high-performance liquid chromatographic method for the measurement of midazolam plasma concentrations during long-term infusion in ICU patients.
abstract: A new high-performance liquid chromatographic method was developed for quantification of midazolam in plasma samples from intensive care unit patients on long-term intravenous infusion of this benzodiazepine. Plasma samples (0.5 ml) were mixed with 1 microgram flurazepam (internal standard), alkalinized with 2.5 N NaOH, and extracted with toluene. The organic phase was evaporated to dryness, and the residue was dissolved in the mobile phase (acetonitrile/0.05 M phosphate buffer pH 4.5) and injected into the analytical column (C18 Nova-Pak 3.9 x 150 mm, 4 microns, maintained at room temperature; mobile phase flow rate: 1.2 ml/minute). The eluate was monitored at 207 nm, which reduced the risk of interferences from concurrent medications. Retention times of flurazepam, 1'-hydroxymidazolam (an active metabolite) and midazolam were approximately 4.5, 6.1 and 13.5 minutes, respectively. The assay was linear over the range 100 to 3000 ng/ml. The coefficients of variation of the within-day and between-day assay for the 100 to 3000 ng/ml range were < 5% and < 7%, respectively. The developed method is fast, reproducible, and well suited to monitor steady state midazolam plasma concentrations in clinical samples.
authors.affiliation: School of Pharmacy, Faculty of Medicine, Catholic University of Louvain, Brussels, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Van Brandt
authors.forename: P
authors.initials: P
authors.lastname: Hantson
authors.forename: P
authors.initials: P
authors.lastname: Mahieu
authors.forename: R K
authors.initials: RK
authors.lastname: Verbeeck
mesh_terms: D018686:Anesthetics, Intravenous / Q000097:blood*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003422:Critical Care; D006801:Humans; D008874:Midazolam / Q000097:blood* / Q000493:pharmacokinetics
chemical_list: D018686:Anesthetics, Intravenous; D008874:Midazolam