Hyponatremia with venlafaxine

OBJECTIVE: To describe a patient with hyponatremia associated with venlafaxine therapy. CASE SUMMARY: A 92-year old white woman who was receiving venlafaxine for management of depression was found to have hyponatremia. A detailed workup confirmed the diagnosis of syndrome of inappropriate antidiuretic hormone secretion (SIADH). A temporal relationship between initiation of venlafaxine therapy and the onset of hyponatremia indicated it as the probable cause. Venlafaxine was discontinued, and hyponatremia resolved with a few weeks. DISCUSSION: Hyponatremia has been reported with selective serotonin-reuptake inhibitors (SSRIs). Serotonin has been reported to elevate concentrations of vasopressin in animal models. Venlafaxine is a potent inhibitor of serotonin reuptake and may have adverse effects similar to those of SSRIs. CONCLUSIONS: We report a case of hyponatremia probably caused by venlafaxine. Awareness of this potential problem would be helpful to clinicians and should be considered in the differential diagnosis of hyponatremia.