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.