Syndrome of Inappropriate Antidiuretic Hormone Secretion and Ibuprofen, a Rare Association to Be Considered: Role of Tolvaptan

The association between the syndrome of inappropriate antidiuretic hormone secretion (SIADH) and the use of nonsteroidal anti-inflammatory drugs (NSAIDs) is rare and has never been treated with an arginine vasopressin receptor antagonist. We report a unique case of SIADH associated with ibuprofen use and successfully treated with tolvaptan. A 76-year-old man came to our observation because of lumbar pain and epigastric discomfort. He was taking ibuprofen orally 400 mg bid as an analgesic treatment. Laboratory tests showed low levels of sodium (116 mmol/L) and chloride; a diagnosis of SIADH was formulated and ibuprofen was stopped immediately. Imaging tests allowed to rule out the presence of malignancies or cerebral and lung diseases. Slightly hypertonic saline infusion was administered for 3 days without significant sodium improvement; therefore, tolvaptan was started at the initial dose of 7.5 mg daily, doubled after 5 days. After 8 days of treatment the patient showed progressive increase of sodium levels up to normal values. In the following weeks tolvaptan was prescribed at progressively titrated dosage to full suspension; afterwards the sodium levels remained normal without any type of treatment.