A sensitive and rapid method for quantification of lacosamide and desmethyl lacosamide by LC-MS/MS

Background: Monitoring lacosamide (LCM) helps optimize therapeutic dosing in some clinical settings. We developed a novel LC-MS/MS method for measuring serum LCM and O-desmethyl lacosamide (ODL). Results/discussion: The sample preparation was protein precipitation with methanol. The total CV was less than 4.7%. Calibration range was 0.95-30.29 mu g/ml and 0.95-30.41 mu g/ml while the expanded linear range was 0.41-47.49 mu g/ml and 0.34-48.17 mu g/ml for LCM and ODL, respectively with analytical accuracy of 87.2-106.0%. 45 random serum samples collected from 23 individuals on either 200 mg/day or 400 mg/day of LCM therapy showed concentrations of 2.2-19.8 mu g/ml for LCM and up to 2.5 mu g/ml for ODL. Conclusion: A simple and sensitive LC-MS/MS assay was validated for quantification of LCM and ODL in human serum.