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.