Abstract
We report a patient who developed syndrome of inappropriate secretion of antidiuretic hormone (SIADH), which may have been caused by carbamazepine. A 75-year old woman with idiopathic trigeminal neuralgia had been treated with carbamazepine and repeated right mandibular nerve blocks. Since the pain could not be controlled with carbamazepine 600 mg/day, she was admitted for mandibular nerve block. The pain worsened on the day of admission. Carbamazepine 100 mg was taken. She became anxious and complained of general malaise, nausea, and headache. Laboratory examination revealed that the concentration of serum sodium was 119 mEq/L. There were low urine output, low serum osmolarity, and high urine osmolarity, suggesting carbamazepine-induced SIADH. Carbamazepine was withdrawn, and water intake was restricted. The serum sodium concentration increased to 135 mEq/L on day 8. Thermocoagulation of the right mandibular nerve relieved the pain. Carbamazepine-induced SIADH is rare but needs attention. When carbamazepine cannot be taken for the treatment of trigeminal neuralgia because of its side effects, treatment with thermocoagulation may be beneficial to control trigeminal neuralgia.
