[Three cases of hyponatremia during administration of pimozide]

Three patients with hyponatremia were found at an residential home of mental developmental delay. Because pimozide had been administered to all of them, it was suggested that pimozide might have induced compulsive water drinking resulting in hyponatremia. To my knowledge, there has been no previous report that pimozide may induce hyponatremia. As children with mental developmental delay and/or autism frequently develop epilepsy, hyponatremia should be included in the differential diagnosis of convulsive seizures. Particularly when antipsychotic drugs such as pimozide have been given, we should pay attention to polydipsia, polyuria and/or general malaise and prevent hyponatremia.