A Comparative Study of the Use of Half-Dose (7.5 MG) Versus Full-Dose (15 MG) of Tolvaptan in the Treatment of Hyponatremia Caused by the Syndrome of Inappropriate Antidiuresis (SIAD)

Background: Hyponatremia (serum sodium levels below 135 mEq/L) is the most prevalent electrolyte imbalance, with the syndrome of inappropriate antidiuresis (SIAD) being the most common cause among inpatients. Fluid restriction is the primary treatment for SIAD, yet its efficacy is inconsistent. A novel therapeutic approach involves the use of oral vaptans, such as tolvaptan (TLV), which are non-peptide antagonists of arginine vasopressin receptors. The recommended daily dose of TLV is 15 mg; however, the risk of overcorrection and osmotic demyelination syndrome must be considered. Methods: Consequently, a more cautious approach involving a 7.5 mg dose of TLV was studied in SIAD patients to determine its safety and efficacy compared with a 15 mg dose. Results: The findings of our investigation show that the results obtained from the two doses are highly similar. However, it is important to note that the risk of overcorrection was lower in the 7.5 mg TLV group than in the 15 mg group. Furthermore, a more gradual increase in serum Na was observed in the 7.5 mg group than in the 15 mg group after the most critical first 24 h. Conclusions: TLV therapy can be initiated with a 7.5 mg dose, with serum sodium levels monitored at 12 and 24 h to confirm or adjust the TLV dose as required.