Objective: To establish the ultra-high performance liquid chromatography (UPLC) method for determination of blood concentration of lacosamide (LCM) in children with epilepsy. Methods: Phenytoin sodium was used as the internal standard. The Waters ACQUITY UPLC BEH C18 column (100 mm×2.1 mm

1.7 µm) was used

the mobile phase was methanol-10 mmol/L ammonium dihydrogen phosphate solution (45∶55

adjusted with formic acid to pH 4.0)

the flow rate was 0.2 mL/min

the injection volume was 2 μL

the detection wavelength was 240 nm

and the column temperature was 30 ℃. Results: The retention time of LCM and propranolol was 2.468 min and 5.475 min

respectively. LCM (X) showed good linearity with peak area (Y) in the concentration range from 1.0 to 40.0 μg/mL (Y=0.049

4X+0.022

2

r=0.999

8)

the lower limit of detection was 0.50 μg/mL (S/N=4) and the lower limit of quantification was 1.00 μg/mL (S/N=12). The intra-day precision was from 1.88% to 3.29%

the inter-day precision was from 2.33% to 5.68%

the accuracy was from 88.75% to 105.29%

and the extraction recovery rate was from 96.58% to 101.76%. The room temperature stability

long-term stability and freeze-thaw stability of LCM samples were good (deviation <15%). Conclusion: The UPLC method has the advantages of simple pre-treatment

high analytical sensitivity

specificity

stability and reliability

and can meet the needs of clinical drug concentration monitoring for LCM treatment.