Analysis of CSF amino acids in young patients with generalised refractory epilepsy during an add-on study with lamotrigine.

The effect of add-on administration of lamotrigine (1-12 mg/kg per day, 2-12 months) on the levels of neurotransmission related amino acids including gamma-aminobutyric acid (GABA), glutamate, aspartate, glycine and antiepileptic drugs (AEDs) in lumbar cerebrospinal fluid (CSF) was studied in 22 children and young adults with generalised therapy resistant epilepsy. Two lumbar punctures were performed, one prior to, and one following a mean of 5 months (2-12 months) of lamotrigine treatment. Lamotrigine decreased seizure incidence and severity in 12 of the 22 patients without influencing CSF GABA, glutamate, aspartate or glycine levels. Lamotrigine did not alter the concentrations of AEDs in CSF or plasma. However, CSF GABA levels were 86% higher in those patients also treated with gamma-vinyl-GABA (vigabatrin, GVG) compared with patients treated with other combinations and this was not altered by co-medication with lamotrigine. The proposed mechanism of action of lamotrigine, namely that it may inhibit glutamate release in the CNS, is not reflected by changes in CSF glutamate levels. The present findings indicate that CSF GABA, glutamate, aspartate and glycine levels may not be useful as in vivo neurochemical markers in young patients responding to the therapeutic dose of lamotrigine used in this study.