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Efficacy of SAMSCA® (tolvaptan): Data from the pivotal clinical trials

SAMSCA significantly increased average daily serum sodium from baseline to Day 4 and baseline to Day 30, vs placebo (P<0.0001) in the SALT (Study of Ascending Levels of Tolvaptan in hyponatremia) trials

  • Primary end point was average daily AUC for change in serum sodium from baseline to Day 4 (tolvaptan [n=213], 4.0 mEq/L; placebo [n=203], 0.4 mEq/L [P<0.0001]) and baseline to Day 30 (tolvaptan [n=213], 6.2 mEq/L; placebo [n=203], 1.8 mEq/L [P<0.0001])

In the SALT (Study of Ascending Levels of Tolvaptan in hyponatremia) pivotal trials—two identical, 30-day, randomized, double-blind, placebo-controlled, multicenter studies—424 patients with euvolemic or 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. Primary end point from pivotal clinical trials was average daily AUC for change in serum sodium from baseline to Day 4 (tolvaptan, 4.0 mEq/L; placebo, 0.4 mEq/L, P<0.0001) and baseline to Day 30 (tolvaptan, 6.2 mEq/L; placebo, 1.8 mEq/L, P<0.0001). Mean change in serum sodium from baseline to 8 hours for tolvaptan, 2.5 mEq/L; placebo, -0.5 mEq/L. P<0.0001 (secondary end point). Starting dose was 15 mg, and was increased to 30 or 60 mg, if necessary. Within 7 days of discontinuation, serum sodium concentrations in tolvaptan-treated patients declined to placebo-like levels.

Compared with placebo, SAMSCA provided a statistically significant increase from baseline (P<0.0001) in serum sodium in patients with euvolemic or hypervolemic hyponatremia

  • Significant increase in as early as 8 hours (mean change from baseline, secondary endpoint)
  • Proven in two identical randomized, placebo-controlled, double-blind phase 3 studies (Study of Ascending Levels of Tolvaptan in hyponatremia 1 and 2)1
  • The mean increases in serum sodium during treatment initiation (first 24 hours) were 4.06 mEq/L for SAMSCA 15 mg and 0.33 mEq/L for placebo (baseline <135 mEq/L)2
Too-rapid correction of serum sodium (e.g., >12 mEq/L/24 hours) can cause serious neurologic sequelae, including osmotic demyelination syndrome (ODS).

SAMSCA significantly increased serum sodium in hyponatremic patients with heart failure

  • Demonstrated in the pooled subgroup analysis of SALT-1 and SALT-2



SAMSCA is indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia (serum sodium <125 mEq/L or less marked hyponatremia that is symptomatic and has resisted correction with fluid restriction), including patients with heart failure and Syndrome of Inappropriate Antidiuretic Hormone (SIADH).

Limitations of Use:

  • Patients requiring intervention to raise serum sodium urgently to prevent or to treat serious neurological symptoms should not be treated with SAMSCA
  • It has not been established that raising serum sodium with SAMSCA provides a symptomatic benefit to patients



  • SAMSCA should be initiated and re-initiated in patients only in a hospital where serum sodium can be monitored closely.
  • 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


  • Because of the risk of hepatotoxicity, tolvaptan should not be used for ADPKD outside of the FDA-approved REMS.


  • Use in patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD) outside of FDA-approved REMS
  • Unable to sense or respond to thirst
  • Hypovolemic hyponatremia
  • Taking strong CYP3A inhibitors
  • Anuria
  • Hypersensitivity (e.g., anaphylactic shock, rash generalized) to tolvaptan or any component of the product

Too Rapid Correction of Serum Sodium Can Cause Serious Neurologic Sequelae: During initiation and after titration monitor patients to assess serum sodium concentrations and neurologic status. 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 a rise in serum sodium, discontinue or interrupt treatment with SAMSCA and consider administration of hypotonic fluid. Fluid restriction during the first 24 hours with SAMSCA may increase the likelihood of overly-rapid correction of serum sodium, and should generally be avoided. Co-administration of diuretics also increases the risk of too rapid correction of serum sodium and such patients should undergo close monitoring of serum sodium.

Liver Injury: Tolvaptan can cause serious and potentially fatal liver injury. In clinical trials, cases of serious liver injury have been attributed to chronically administered tolvaptan in patients with ADPKD. Liver failure requiring transplantation has been reported in postmarketing experience with tolvaptan in ADPKD. Limit duration of therapy with SAMSCA to 30 days. Avoid use in patients with underlying liver disease, including cirrhosis, because the ability to recover may be impaired.

Dehydration and Hypovolemia: In patients who develop medically significant signs or symptoms of hypovolemia, discontinuation is recommended. Dehydration and hypovolemia can occur, especially in potentially volume-depleted patients receiving diuretics or those who are fluid restricted

Co-administration with Hypertonic Saline: Not recommended

Drug Interactions – CYP3A Inhibitors: Tolvaptan is a substrate of CYP3A. Moderate to strong CYP3A inhibitors can lead to a marked increase in tolvaptan concentrations. Do not use SAMSCA with strong inhibitors of CYP3A and avoid concomitant use with moderate CYP3A inhibitors. Patients should avoid grapefruit juice beverages while taking SAMSCA

Hyperkalemia or Drugs that Increase Serum Potassium: Monitor serum potassium levels in patients with a serum potassium >5 mEq/L and in patients receiving drugs known to increase serum potassium levels

Acute Urinary Retention with Outflow Obstruction: Patients with partial obstruction of urinary outflow have an increased risk of developing acute retention. Do not administer tolvaptan in patients with uncorrected urinary outflow obstruction.

Adverse Reactions: The most common adverse reactions (SAMSCA incidence  ≥5% more than placebo, respectively): thirst (16% vs 5%), dry mouth (13% vs 4%), asthenia (9% vs 4%), constipation (7% vs 2%), pollakiuria or polyuria (11% vs 3%) and hyperglycemia (6% vs 1%)

Gastrointestinal Bleeding in Patients with Cirrhosis: In patients with cirrhosis in the hyponatremia trials, GI bleeding was reported in 10% of tolvaptan-treated patients vs 2% for placebo

Other Drug Interactions:

  • Strong CYP3A Inducers: Co-administration of SAMSCA with strong CYP3A inducers reduces exposure to SAMSCA. Avoid concomitant use of SAMSCA with strong CYP3A inducers
  • Angiotensin Receptor Blockers, Angiotensin Converting Enzyme Inhibitors and Potassium Sparing Diuretics: In clinical studies, adverse reactions of hyperkalemia were approximately 1 to 2% higher when tolvaptan was administered with angiotensin receptor blockers, angiotensin converting enzyme inhibitors and potassium sparing diuretics compared to administration of these medications with placebo. Serum potassium levels should be monitored during concomitant drug therapy.
  • V2-Receptor Agonist: Tolvaptan interferes with the V2-agonist activity of desmopressin (dDAVP). Avoid concomitant use of SAMSCA with a V2-agonist

Pregnancy and Lactation: Based on animal data, SAMSCA may cause fetal harm. Advise women not to breastfeed during treatment with SAMSCA.

To report SUSPECTED ADVERSE REACTIONS, contact Otsuka America Pharmaceutical, Inc. at 1-800-438-9927 or FDA at 1-800-FDA-1088 (





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. SAM-136. Otsuka America Pharmaceutical, Inc.
Data on file. SAM-135. Otsuka America Pharmaceutical, Inc.