Tolvaptan in SIADH Treatment

Mechanism and Indications

Tolvaptan is a selective vasopressin V2-receptor antagonist that blocks the effects of antidiuretic hormone, increasing free water excretion and improving serum sodium levels in SIADH, as indicated by the European licensing for treatment of SIADH specifically 1
In Europe, tolvaptan is only licensed for treatment of SIADH specifically, not for all causes of hyponatremia, with a mechanism of action involving the blockade of vasopressin V2-receptors 1

Studies demonstrate that tolvaptan administration for short periods (1 week to 1 month) is associated with increased urine volume and improved serum sodium levels in 45-82% of patients, with a significant improvement in serum sodium concentration by the fourth day of treatment 1
In patients with liver cirrhosis, tolvaptan (15-60 mg) showed significant improvement in serum sodium concentration by the fourth day of treatment, maintained until the 30th day, according to the Clinical and Molecular Hepatology 2, 3

Common side effects of tolvaptan include thirst, dry mouth, polyuria, and pollakiuria, as reported in the Journal of Hepatology 1
Tolvaptan is contraindicated in patients with hypovolemic hyponatremia, as stated in the Journal of Hepatology 4
Tolvaptan is also contraindicated in patients with anuria, as indicated in the journal Neurosurgery 5

Patient selection for tolvaptan treatment should involve confirmation of SIADH diagnosis with euvolemic hyponatremia, as recommended by the journal Chest 6
The American Thoracic Society and other guideline societies may provide recommendations for the use of tolvaptan in SIADH, although specific guidelines are not mentioned in the provided text, tolvaptan treatment should be initiated in a hospital setting with close monitoring of serum sodium levels 1

Fluid restriction (1.0-1.5 L/day) remains first-line for mild to moderate hyponatremia, as supported by the Journal of Hepatology and Clinical and Molecular Hepatology 3, 4
Administration of plasma expanders such as albumin may be considered for SIADH management, according to the Clinical and Molecular Hepatology 3
For severe symptomatic hyponatremia, hypertonic (3%) saline may be used, as indicated in the journal Neurosurgery 5, 7