Increasing plasma sodium with Tolvaptan under regulated water intake: comparison with hypertonic saline
Nabil William Sweis1, Jennifer Tuazon1, Yusra Cheema1
1Division of Nephrology and Hypertension, Department of Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, United States.
American Journal of Physiology. Renal Physiology
|March 26, 2026
Summary
Tolvaptan, a vasopressin antagonist, can safely control plasma sodium increases in hyponatremia treatment by regulating water intake. This method offers a more physiological approach to correcting low sodium levels.
Area of Science:
- Nephrology
- Endocrinology
- Pharmacology
Background:
- Hyponatremia treatment carries a risk of osmotic demyelination from rapid plasma sodium increases.
- A strategy using vasopressin antagonists like Tolvaptan and controlled water intake was proposed to manage sodium rise rate.
Purpose of the Study:
- To evaluate the efficacy of Tolvaptan in controlling plasma sodium levels.
- To compare Tolvaptan's effect on sodium and osmolality with hypertonic saline infusion.
Main Methods:
- Healthy male subjects received either 30 mg or 60 mg of Tolvaptan.
- Water intake was regulated hourly to match urine output minus 5 ml/kg body weight.
- A 6-hour infusion of 3% saline was administered for comparison.
Main Results:
- Tolvaptan significantly decreased urine osmolality and increased free water clearance and urine output.
- Plasma sodium increased to approximately 144 mEq/L with both Tolvaptan doses over 6 hours.
- The rise in plasma sodium and osmolality with Tolvaptan was similar to that achieved with hypertonic saline infusion.
Conclusions:
- Tolvaptan facilitates a controlled increase in plasma sodium when water intake is regulated.
- This approach may benefit hyponatremia patients by reducing excess body water physiologically.
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