Hyponatraemia associated with lamotrigine in cranial diabetes insipidus

We report the cases of two children with cranial diabetes insipidus who wer e treated with lamotrigine for seizures and who had accompanying changes in desmopressin requirements, Lamotrigine is a new anticonvulsant chemically unrelated to other existing antiepileptic drugs, Studies suggest it acts at voltage-sensitive sodium channels and also decreases calcium conductance. Both of these mechanisms of action are shared by carbamazepine, which can c ause hyponatraemia secondary to inappropriate secretion of antidiuretic hor mone. It is possible that me effect or lamotrigine on fluid balance in the cases described is also centrally mediated.