 Patients treated with the antiepileptic drug Oxcarbazepine often develop syndrome of inappropriate secretion of antidiuretic hormoneSIADHWe want to test the hypothesis, that these patients have a higher reabsorption of water during the Aquaporine2 water channels,a higher concentration of Vasopressine AVP, and a lower clearance of water.This situation will tend to normalize, when the patients are treated with fluid restriction 