Direct Chiral HPLC-MS/MS Method for Determination of R-Lacosamide in Human Plasma

Abstract

R-Lacosamide (RLC) is a new approved antiepileptic drug for adjunctive use and monotherapy for partial-onset seizures in some countries. RLC use in other epilepsies and diseases is under study. Research is also going on the activities exhibited by the S-enantiomer (SLC). Taking into consideration further perspectives, the development of direct chiral method that can selectively estimate R-isomer in the presence of S-isomer from human plasma is needed. Plasma samples were spiked with RLC, deuterated internal standard, and SLC. Deuterated RLC as the internal standard enabled us to precisely measure the concentration of RLC by minimizing variations associated with the extraction, ionization, and separation. Target compounds were recovered by liquid-liquid extraction from human plasma using methyl tert-butyl ether. The percentage recovery was found to be 68%.The isomers were resolved completely using DIACEL-IC3 column in the reverse phase mode. The retention times of R- and S-isomers were found to be 6.20 ± 0.5 and 8.00 ± 0.5 min, respectively. The proposed method was found to be linear in a concentration range from 1.00 × 102 to 1.50 × 104 ng/mL. Direct chiral HPLC tandem mass spectrometric method that can quantify R-lacosamide in the presence of S-isomer from human plasma without any carry-over and matrix effects was successfully developed. This method is very simple, fast, economic, sensitive, and validated as per EMA guidelines.