The letter discusses two cases of psychotropic drug-induced fetal hypernatremia with a history of antipsychotic-induced hyponatremia. The first case is a 48-year-old woman with 30 year history of schizophrenia hospitalized for relapse due to poor compliance. The second case is a 80-year-old male patient with schizophrenia found with confusion 30 days after he was prescribed with clonazepam 4 milligram per day added to antipsychotics.