Olanzapine-Induced Hyponatremia Presenting with Seizure Requiring Intensive Care Unit Admission

Rapid-onset hyponatremia is a rare, but potential, complication of olanzapine treatment. Hyponatremia, secondary to atypical antipsychotic use, has been reported in many case reports and is thought to be associated with a syndrome of inappropriate anti-diuretic hormone secretion (SIADH). Psychogenic polydipsia is a separate cause of hyponatremia, which is also seen in the psychiatric population, particularly in schizophrenia, and must be differentiated from SIADH. We report a case of sudden-onset hyponatremia resulting in seizure onset necessitating intensive care unit admission in a patient taking olanzapine during hospitalization in a psychiatric unit. Clinicians should be aware of the association between olanzapine and hyponatremia secondary to SIADH or psychogenic polydipsia. As in our case, the patient status may decline rapidly, resulting in seizure onset. Physicians should actively monitor patients taking antipsychotics for changes in serum sodium levels.