title: A novel enantioselective microassay for the high-performance liquid chromatography determination of oxcarbazepine and its active metabolite monohydroxycarbazepine in human plasma.
abstract: A simple and innovative assay is described that allows the determination of the antiepileptic drug oxcarbazepine and the chiral separation of the two enantiomers of its active metabolite monohydroxycarbazepine (licarbazepine). The assay requires liquid-liquid extraction of the sample (200 microL) into tert-butyl methyl ether and dichloromethane, drying of the organic phase under a nitrogen stream, reconstitution with the mobile phase, and injection in the high-performance liquid chromatography system after filtering. Separation of oxcarbazepine, R-(-)-monohydroxycarbazepine, S-(+)-monohydroxycarbazepine, and the second-step metabolite 10,11-trans-dihydroxycarbamazepine (racemate) is achieved with a Chiralcel ODR column and potassium hexafluorophosphate/acetonitrile as mobile phase. Detection is by ultraviolet absorbance at 210 nm. Standard curves are linear (r2 > or = 0.999) over the range of 0.1 to 25 microg/mL for each analyte with a limit of quantification of 0.1 microg/mL (1 ng injected) for all compounds. Within-day and between-day precision is better than 12% and within-day and between-day accuracy is between 99% and 116% for each compound. These performance characteristics are adequate for pharmacokinetic studies and for therapeutic drug monitoring. However, because the two enantiomers of monohydroxycarbazepine exhibit similar pharmacologic activity, nonenantioselective assays are likely to be more cost-effective for therapeutic drug monitoring purposes.
authors.affiliation: Clinical Pharmacology Unit, Department of Internal Medicine and Therapeutics, University of Pavia, Pavia, Italy.
authors.forename: Iolanda
authors.initials: I
authors.lastname: Mazzucchelli
authors.forename: Valentina
authors.initials: V
authors.lastname: Franco
authors.forename: Cinzia
authors.initials: C
authors.lastname: Fattore
authors.forename: Roberto
authors.initials: R
authors.lastname: Marchiselli
authors.forename: Emilio
authors.initials: E
authors.lastname: Perucca
authors.forename: Giuliana
authors.initials: G
authors.lastname: Gatti
mesh_terms: D000927:Anticonvulsants / Q000097:blood / Q000378:metabolism*; D002220:Carbamazepine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003984:Dibenzazepines / Q000097:blood*; D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D000078330:Oxcarbazepine
chemical_list: D000927:Anticonvulsants; D003984:Dibenzazepines; D002220:Carbamazepine; D000078330:Oxcarbazepine; C428744:10,11-dihydro-10-hydroxy-5H-dibenz(b,f)azepine-5-carboxamide