SIADH and Severe Hyponatremia Induced by Antipsychotic Drug

Abstract

Background: Hyponatremia is the most common electrolyte disturbance encountered in clinical practice associated with significant morbidity and mortality. Common cause of hyponatremia is the syndrome of inappropriate antidiuretic hormone secretion (SIADH), a condition characterized by dilutionalhyponatremia due to unregulated secretion of antidiuretic hormone. In psychiatric patients SIADH is common adverse effect of antipsychotic drugs. Despite being common electrolyte disturbance, hyponatremia is frequently unrecognized and untreated in psychiatric patients. Case presentation: A 44-year old male with schizophrenia was admitted to our department following seizure and secondarily developed rhabomyolysis due to severe hyponatremia. He was receiving valproic acid, olanzapine and benzodiazepine for many years. On physical examination the patient was euvolemic and had no evidence of pulmonary, cardiac, renal, thyroid and adrenal disease. After excluding psychogenic polydipsia and other common causes of hyponatremia, a diagnosis of drug induced SIADH was established on the basis of hyponatremia, serum hypoosmolality, high urine specific gravity and high urine sodium concentration. Antipsychotic drugs were discontinued; fluid restriction and hypertonic fluid were administered. Correction of hyponatremia ensued on the third hospital day. Conclusion: Monitoring of the plasma sodium concentration in patients receiving antipsychotic drugs is recommended in order to avoid potentially fatal complication of hyponatremia.