Determination of lamotrigine and its metabolites in human plasma by liquid chromatography-mass spectrometry.
A method based on electrospray ionization liquid chromatography-mass spectrometry was developed for the quantitative determination of lamotrigine and three of its reported metabolites, lamotrigine-2-N-glucuronide, lamotrigine-2-N-methyl, and lamotrigine-2-N-oxide in human blood plasma. The method utilized sample preparation by precipitation of proteins with acetonitrile, chromatographic separation on a reversed-phase system by gradient elution, and monitoring of the protonated molecular ions. Two internal standards, 3,5-diamino-6-(2-methoxyphenyl)-1,2,4-triazine and morphine-3-glucuronide-D3, were utilized to achieve precise quantification. The method validation comprised a demonstration of an agreement in the quantification of lamotrigine with that of a routine HPLC-UV method. The limits of detection were between 0.05 and 0.16 micromol/L. The method was employed for the measurement of clinical samples collected from 55 patients in steady-state prior to the dose intake (trough level). Lamotrigine and the 2-N-glucuronide were typically detected, while the N-methyl and N-oxide metabolites were detected only rarely. The median lamotrigine plasma level was 24.0 micromol/L (range, 4.3 to 64 micromol/L), the median 2-N-glucuronide level was 2.4 micromol/L (range, <0.05 to 24 micromol/L), and the median lamotrigine 2-N-glucuronide/lamotrigine ratio was 0.11 (range, <0.01 to 0.64). In conclusion, this liquid chromatographic-mass spectrometric method is suitable for simultaneous determination of lamotrigine and its metabolites in human plasma.
Beck
Olof
O
Department of Medicine, Division of Clinical Pharmacology, Karolinska University Hospital, Sweden. olof.beck@karolinska.se
Ohman
Inger
I
Nordgren
Helena K
HK
D000927:Anticonvulsants / Q000097:blood / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D000077213:Lamotrigine; D013058:Mass Spectrometry / Q000379:methods*; D014227:Triazines / Q000097:blood / Q000378:metabolism*
D000927:Anticonvulsants; D014227:Triazines; D000077213:Lamotrigine