Modulation of serum concentrations of melatonin by carbamazepine and valproate

Evidence has accumulated about the involvement of reactive oxygen species (ROS) in epilepsy. The neuromodulator melatonin has been shown to reduce oxidative stress in various animal models due to its free radical scavenging properties. The present study investigated whether carbamazepine and valproate alter serum concentrations of melatonin. Epileptic children were randomly assigned to receive carbamazepine/ valproate monotherapy till 22 patients were recruited in the study. At the tenth day, in the evening, samples were drawn for baseline endogenous melatonin estimation. The patients were then administered exogenous melatonin, and repeat samples were drawn after 30 minutes. Serum levels of melatonin were estimated using Melatonin ELISA kits. The median levels of melatonin were 165.0 pg/ml (Range 50.0-350.0) in CBZ+MEL group and 78.0 pg/ml (Range 13.0-260.0) in the VPA+MEL group. The observed difference in melatonin levels could be attributed to the difference in antiepileptic drugs, additive increase in reactive oxygen species due to disease combined with carbamazepine, or possibly to a difference in melatonin kinetics in conditions of oxidative stress.