Lacosamide is registered for the treatment of (partial-onset) seizures in adults and children > 2 years of age, with a recommended maximum dose of 12 mg kg-1 in two doses. It is generally well tolerated. We present a case of a prematurely born neonate with refractory seizures despite multiple anti-epileptic drugs due to a denovo SCN2A mutation. Lacosamide was added, and serial plasma trough levels were measured to optimize the dose. Based on the available literature, the dose needed to achieve a therapeutic plasma trough level in our patient was much higher than expected, with a dose of 22 mg kg-1 in 4 doses. No side effects were observed. In specific cases in the neonatal population, lacosamide is safe and well-tolerated and should be considered as a treatment option under strict serum surveillance of plasma through levels and cardiac monitoring. Further research is needed to generalize these results and develop adjusted dose guidelines in the neonatal population.