Syndrome of inappropriate secretion of antidiuretic hormone due to citalopram and venlafaxine.

INTRODUCTION: Selective serotonin reuptake inhibitors (SSRIs) and venlafaxine are often used to treat depression in the elderly due to their low incidence of side effects. All five of the SSRIs currently available and venlafaxine have been associated with hyponatremia.

CASE REPORT: This article describes the case of an 87-year-old man with depression who presented with hyponatremia after starting treatment with citalopram. After excluding other common causes of hyponatremia, a diagnosis of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was confirmed. Sodium levels returned to the normal range following discontinuation of citalopram. Subsequently, due to the persistence of depression, treatment with venlafaxine was initiated. Three weeks later, hyponatremia associated with SIADH was once again diagnosed and venlafaxine was discontinued. The hyponatremia resolved in 2 weeks.

DISCUSSION: Both SSRIs and venlafaxine have been associated with SIADH in numerous case reports and retrospective studies. Risk factors for developing hyponatremia with these drugs are advanced age and treatment with other medications. To our knowledge, this is the first case report in which SIADH was associated with two different families of antidepressants in the same patient.

CONCLUSION: Physicians should be aware of the risk of hyponatremia when prescribing SSRIs and venlafaxine in elderly patients with multiple drug therapies. Sodium levels should be monitored during treatment.