Topiramate effects on plasma serotonin levels in children with epilepsy.

Topiramate (TPM) is a new, effective and safe antiepileptic drug. TPM is also effective in treating a wide spectrum of conditions such as eating disorders and related anomalies, bulimia nervosa and other conditions in which serotonin (5-hydroxytryptamine, 5-HT) is involved pathogenetically. Plasma serotonin mainly derives from blood platelets, which represent a valid model of serotoninergic neurons. We measured plasma 5-HT levels in 12 children affected by epilepsy who underwent TPM therapy. Inclusion criteria were (i) age range 2-12 years, (ii) weight greater than 12 kg, (iii) no more than one antiepileptic drug used when TPM therapy was instituted, and (iv) a minimum study period of 3 months. After a mean period of 3 months of TPM treatment, a significant increase in mean plasma serotonin levels was observed with respect to the basal levels and those of a control group. There were no significant correlations between the changes in serotonin concentrations and the antiepileptic efficacy or doses of TPM used. TPM may influence serotonin metabolism in children affected by epilepsy. Further studies are needed to establish whether these serotonin plasma changes represent an epiphenomenon or indicate direct effects of TPM on the serotoninergic system.