SIADH Triggered by Duloxetine in a Patient with ACNES: A Cautionary Lesson for Pain Physicians

Abstract Duloxetine is commonly used in chronic pain management, especially for neuropathic and abdominal wall pain syndromes. Although generally well tolerated, it may occasionally provoke hyponatremia through the syndrome of inappropriate antidiuretic hormone secretion (SIADH). We describe a 59-year-old woman receiving duloxetine for persistent right hypochondrial pain later diagnosed as anterior cutaneous nerve entrapment syndrome. She presented with worsening pain and profound hyponatremia (117 mmol/L). Prior investigations, including extensive imaging and multiple pain interventions, had not revealed a structural pathology. Laboratory findings in the current admission were consistent with SIADH, and she had a history of a previous intensive care unit stay for unexplained hyponatremia. Her sodium normalized after discontinuing duloxetine and initiating supportive therapy. This case highlights the importance of routinely checking serum sodium in patients on duloxetine, particularly in those with chronic pain, where symptoms of hyponatremia may easily be missed.