title: Measurement by HPLC of midazolam and its major metabolite, 1-hydroxymidazolam in plasma of very premature neonates.
abstract: A simple, selective high-performance liquid chromatographic method with ultraviolet detection at 220 nm is described for quantitation of midazolam and its primary metabolite 1-hydroxymidazolam in 100 microL plasma samples from premature infants. A mobile phase of acetonitrile:tetrahydrofuran:phosphate buffer (0.01 M, pH 6.7) (35:5:60 v/v) was pumped at 1 mL/min through a C8 Symmetry (150 x 3.9 mm) column. Plasma (100 microL) was extracted with 10% v/v isopropyl alcohol in dichloromethane containing 25 ng/mL climazolam (internal standard, IS) followed by back extraction into phosphoric acid (0.02 M). 1-Hydroxymidazolam, midazolam, and climazolam (IS) were eluted at 4.9, 7.4, 8.4 min, respectively. Recoveries were > 70%. Calibration curves in blank plasma were linear (r > 0.999) from 12.5 to 800 ng/mL. Within-day and between-day imprecision (CV%) was 1.8-6.5%, and 4.1-8.8%, respectively. Inaccuracy was 12.3%. Application of the method was demonstrated by a pharmacokinetic analysis of midazolam and 1-hydroxymidazolam in plasma drawn from 15 premature neonates after a single intravenous dose of midazolam (0.1 mg/kg).
authors.affiliation: Department of Pharmacy, University of Queensland, Australia.
authors.forename: T C
authors.initials: TC
authors.lastname: Lee
authors.forename: B
authors.initials: B
authors.lastname: Charles
mesh_terms: D014151:Anti-Anxiety Agents; D001569:Benzodiazepines; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000097:blood*; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood*; D008297:Male; D008874:Midazolam / Q000031:analogs & derivatives* / Q000097:blood; D015203:Reproducibility of Results; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet
chemical_list: D014151:Anti-Anxiety Agents; D006993:Hypnotics and Sedatives; D012996:Solutions; D001569:Benzodiazepines; C040081:1-hydroxymethylmidazolam; C035147:climazolam; D008874:Midazolam