Which medications are known to cause SIADH?

• A. Hydrochlorothiazide
• B. Selective serotonin reuptake inhibitors
• C. Tricyclic antidepressants
• D. All of the above

Answer: (D)

Drug-induced SIADH happens when a medication causes inappropriately high release or action of antidiuretic hormone, leading to water retention and dilutional hyponatremia with concentrated urine. Among medications known to provoke this are selective serotonin reuptake inhibitors, tricyclic antidepressants, and hydrochlorothiazide. SSRIs increase serotonin, which can stimulate ADH release and/or enhance the kidney’s response to ADH, producing euvolemic hyponatremia. TCAs can have a similar effect by promoting ADH release or amplifying its renal effects, particularly in older patients. Thiazide diuretics like hydrochlorothiazide can precipitate hyponatremia through volume depletion and heightened ADH activity, which can resemble SIADH. Because of these mechanisms, all of these medication classes have been linked to SIADH. If suspected, reviewing the drug regimen and addressing the offending agent is a key step in management.