Low-dose Quetiapine-induced Syndrome of Inappropriate Antidiuretic Hormone in a Patient with Traumatic Brain Syndrome

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by hyponatremia, low serum osmolality, and clinical euvolemia in the absence of diuretic medication. And the causes of SIADH are various, antipsychotic agents and traumatic brain injury (TBI) are well known. Quetiapine is often chosen to manage the maladaptive behavior of patients with post-TBI. Although a previous study reported that quetiapine doses ranging from 25 to 300 mg were effective and tolerable, the symptoms of the patient might be aggravated. The symptoms of TBI such as nausea, malaise, headache, lethargy, and mild cognitive deficits are similar to those of SIADH. So the differentiation between SIADH and TBI may be difficult. This paper reports a case of SIADH in a patient with a TBI after using a small dose of 25 to 50 mg quetiapine.