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- Significant increase in as early as 8 hours
- Results consistent across etiologies
- Reduced need for fluid restriction
- Importance of appropriate correction
- Long-term use
Significant increase in as early as 8 hours
Proven in two identical randomized, placebo-controlled, double-blind phase 3 studies (Study of Ascending Levels of Tolvaptan in hyponatremia 1 and 2) [SALT-1 and SALT-2]1
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Results consistent among patients with heart failure, cirrhosis, and SIADH
The average rates of serum sodium correction during the treatment initiation (first 24 hours) were 3.83 mEq/L for SAMSCA (15 mg) and 0.30 mEq/L for placebo2
- Too rapid correction of serum sodium (e.g., >12 mEq/L/24 hours) can cause serious neurologic sequelae, including osmotic demyelination syndrome (ODS)
A total of 424 patients with euvolemic and hypervolemic hyponatremia (serum sodium <135 mEq/L) were treated for 30 days with tolvaptan or oral placebo, then followed for an additional 7 days after withdrawal. The primary endpoint for these studies was the average daily AUC for change in serum sodium from baseline to day 4 (tolvaptan, 4.0 mEq/L vs placebo, 0.4 mEq/L) and baseline to day 30 (tolvaptan, 6.2 mEq/L vs placebo, 1.8 mEq/L) in patients with a serum sodium <135 mEq/L. Patients received either tolvaptan or placebo, at a starting dose of 15 mg. The dosage of tolvaptan or placebo was increased to 30 mg or 60 mg, if necessary. During the 7-day discontinuation/follow-up period, serum sodium concentrations in patients treated with tolvaptan declined to placebo-like levels.1,2
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Reduced need for fluid restriction
- Fluid restriction during the first 24 hours of therapy with SAMSCA may increase the likelihood of overly rapid correction of serum sodium and should generally be avoided
- Significantly fewer patients treated with SAMSCA (30/215, 14%) required fluid restriction compared with the placebo group (51/206, 25%) (P<0.01)
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Importance of appropriate serum sodium correction
- Too-rapid correction of hyponatremia (e.g., >12 mEq/L/24 hours) can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death. In susceptible patients, including those with severe malnutrition, alcoholism or advanced liver disease, slower rates of correction may be advisable
- In placebo-controlled clinical trials in patients with hyponatremia, 2% of SAMSCA-treated patients with serum sodium <130 mEq/L had an increase greater than 12 mEq/L at 24 hours, while no patient receiving placebo had a rise greater than 12 mEq/L at 24 hours
- In controlled clinical trials at 8 hours (serum sodium <130 mEq/L), 7% of SAMSCA-treated patients had an increase in serum sodium greater than 8 mEq/L vs 1% of placebo-treated patients
- None of the patients in these studies had evidence of osmotic demyelination syndrome (ODS) or related neurologic sequelae but such complications have been reported following too-rapid correction of serum sodium
- Subjects with SIADH or very low baseline serum sodium concentrations may be at greater risk for too-rapid correction of serum sodium.
- In patients receiving SAMSCA who develop too-rapid rise in serum sodium, discontinue or interrupt treatment with SAMSCA and consider administration of hypotonic fluid
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Long-term use of SAMSCA maintained serum sodium concentrations
- SALTWATER trial was a 4-year sequential, open-label extension of the randomized, placebo-controlled, double-blind Study of Ascending Levels of Tolvaptan in Hyponatremia (SALT-1 and SALT-2)3
- Improvements sustained in many patients for at least 1 year and in some patients for up to 4 years3
- In SALTWATER, a multicenter, open-label extension of the Study of Ascending Levels of Tolvaptan in Hyponatremia (SALT-1 and SALT-2), hyponatremic patients (N=111) received oral tolvaptan for a mean follow-up of 701 days, providing 77,369 patient-days of exposure3
- A total of 111 patients previously on tolvaptan or placebo therapy in SALT-1 or SALT-2 were given tolvaptan as a titrated regimen (15 to 60 mg once daily) after having returned to standard care for at least 7 days; 94 of these patients were hyponatremic (serum sodium <135 mEq/L). By the time of study entry, patients' baseline mean serum sodium concentration had fallen to between their original baseline and post-placebo therapy level
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References:
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Schrier RW, Gross P, Gheorghiade M, et al; SALT Investigators. Tolvaptan, a selective oral vasopressin
V2-receptor antagonist, for hyponatremia. N Engl J Med. 2006;355(20):2099-2112. - Data on file. Otsuka America Pharmaceutical, Inc.
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Berl T, Quittnat-Pelletier F, Verbalis JG, et al; SALTWATER Investigators. Oral tolvaptan is safe and effective in chronic hyponatremia.
J Am Soc Nephrol. 2010;21(4):705-712.
