Association of SIADH with selective serotonin reuptake inhibitors

While SSRIs have been reported to cause SIADH, the actual incidence remains unclear. From the published case reports, the elderly may appear to be at higher risk of developing SIADH. Symptomatic and laboratory presentation in these patients includes lethargy, hyponatremia, elevated urinary sodium excretion, and hyperosmolar urine. However, evaluation of SSRI-induced SIADH has been incomplete. Normalization of serum sodium concentrations occurred after discontinuation of the SSRI and/or fluid restriction. Of the published reports, only three convincingly demonstrated a causative role of SSRI-induced SIADH by rechallenge. As a result, the published case reports cannot definitely established a causal relationship. Pharmacists can play an important role in the care of patients with suspected SSRI-induced SIADH. Pharmacists should be familiar with the clinical and biochemical presentation of SIADH as well as the limitations of published case reports implicating SSRIs as a cause of SIADH. A complete medication history, including when these agents were initiated or discontinued, should be taken. Pharmacists must understand, recognize, and ensure the proper monitoring parameters, namely daily fluid intake, patient weight, and serum sodium concentrations.