Validated assay for quantification of oxcarbazepine and its active dihydro metabolite 10-hydroxycarbazepine in plasma by atmospheric pressure chemical ionization liquid chromatography/mass spectrometry.
Oxcarbazepine (OX), a new antiepileptic, may lead to unwanted side-effects or even life-threatening intoxications after overdose. Therefore, a validated liquid chromatographic/mass spectrometric (LC/MS) assay was developed for the quantification of OX and its pharmacologically active dihydro metabolite (dihydrooxcarbazepine, DOX, often named 10-hydroxycarbazepine). OX and DOX were extracted from plasma by the authors' standard liquid/liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. The compounds were quantified in the selected-ion monitoring mode using atmospheric pressure chemical ionization electrospray LC/MS. The assay was fully validated. It was found to be selective. The calibration curves were linear from 0.1 to 50 mg l(-1) for OX and DOX. Limits of quantification were 0.1 mg l(-1) for OX and DOX. The absolute recoveries were between 60 and 86%. The accuracy and precision data were within the required limits. The analytes in frozen plasma samples were stable for at least 1 month. The method was successfully applied to several authentic plasma samples from patients treated or intoxicated with OX. The measured therapeutic plasma levels ranged from 1 to 2 mg l(-1) for OX and from 10 to 40 mg l(-1) for DOX. The validated LC/MS assay proved to be appropriate for quantification of OX and DOX in plasma for clinical toxicology and therapeutic drug monitoring purposes. The assay is part of a general analysis procedure for the isolation, separation and quantification of various drugs and for their full-scan screening and identification.
Department of Experimental and Clinical Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Saarland, D-66421 Homburg (Saar), Germany. hans.maurer@uniklinik-saarland.de
Hans H
HH
Maurer
Carsten
C
Kratzsch
Armin A
AA
Weber
Frank T
FT
Peters
Thomas
T
Kraemer
D000927:Anticonvulsants / Q000097:blood*; D002138:Calibration; D002220:Carbamazepine / Q000031:analogs & derivatives* / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D000078330:Oxcarbazepine; D012015:Reference Standards; D015203:Reproducibility of Results
C039775:10,11-dihydro-10-hydroxycarbamazepine; D000927:Anticonvulsants; D007202:Indicators and Reagents; D002220:Carbamazepine; D000078330:Oxcarbazepine