Rapid-onset hyponatremia and delirium following duloxetine treatment for postherpetic neuralgia: Case report and literature review

RATIONALE: Hyponatremia following duloxetine treatment has been reported in patients with major depressive disorder, fibromyalgia, diabetic neuropathy, or sciatic pain. The manifestations of duloxetine-induced hyponatremia are varying in different individuals. The overall prognosis for this type of hyponatremia is favorable if properly managed. PATIENT CONCERNS AND DIAGNOSES: Herein, we reported rapid-onset hyponatremia and delirium in an older patient after 2 doses of duloxetine, which was used to control his postherpetic neuralgia. Laboratory examinations revealed a rapid decline in serum sodium level and indicated the possibility of syndrome of inappropriate antidiuretic hormone (SIADH). INTERVENTIONS: Discontinuation of duloxetine, restriction of water intake, and intravenous supplement of normal saline were adopted to manage the hyponatremia. OUTCOMES: Serum concentration of sodium gradually normalized following aforementioned strategies. LESSONS: Special attention to the electrolyte abnormality is recommended in old patients undergoing duloxetine treatment.