Lacosamide Lowers Valproate and Levetiracetam Levels

Background: Lacosamide (LCM) has no known drug interaction or metabolic enzyme induction and is, thus, a good add-on medication. Here we report for the first time that LCM can lower valproate (VPA) and levetiracetam (LEV) serum levels. Methods and Results: Treatment was given to a 14-year-old patient with focal epilepsy without secondary generalization secondary to an intracranial dysembryoplastic neuroepithelial tumor (DNET) without renal or hepatic insufficiency. LCM treatment was initiated in addition to VPA and LEV medication to control seizure activity. Unexpectedly, serum levels of VPA and LEV were significantly reduced during each LCM increase. VPA and LEV doses were increased, and an increase of serum levels was shown. Further increase of LCM resulted in a relevant decrease of both drug serum levels; subsequently, both the VPA and LEV doses were increased. No significant adverse effects were observed. Serum levels under a continuous medication for 12 weeks were stable. Seizure activity was reduced to 50% during the first administration week of LCM and after each increase of LCM. The latter effect lasted only for up to one week. VPA and LEV after their lowered plasma level was detected and taken care of. Conclusion: We could not find any previous case with a drug interaction between LCM and LEV or VPA. An association between initiation of LCM and later increase of the LCM dose and a reduction of the LEV and VPA levels was observed.