Syndrome of psychosis,intermittent hyponatremia and polydipsia is a water-electrolyte disturbance observed in some psychotic patients, mainly with schizophrenia or schizoaffective disorder. Hyponatremia may be the first symptom of that syndrome and in some cases it leads into neurological syndrome named water intoxication. Some medicines in different mechanism may cause PIP-syndrome, including antipsychotics and anticonvulsant drugs. The treatment is based on waterelectrolyte disturbances correction, applying synthetic vasopressin and steroids. This report describes the case of schizoaffective disorders inpatient, with PIP-syndrome caused by thioridazine and carbamazepine. Treating with synthetic vasopressin exacerbated the disturbance, likewise the trial of changing CBZ into OCBZ. The other anticonvulsant drugs used in this patient caused withdrawal of PIP-syndrome, what suggest that the reason of it was CBZ and OCBZ.