Samsca (tolvaptan) is a selective vasopressin V2-receptor antagonist indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia. It is specifically designed to address serum sodium imbalances in patients with conditions such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), heart failure, and cirrhosis. By promoting aquaresis—the electrolyte-sparing excretion of free water—Samsca helps raise serum sodium concentrations in a controlled manner, supporting patient stabilization and improving clinical outcomes. Its targeted mechanism offers a valuable therapeutic option under careful medical supervision.

Features

• Contains tolvaptan, a selective vasopressin V2-receptor antagonist
• Available in 15 mg and 30 mg oral tablets
• Promotes electrolyte-free water excretion (aquaresis)
• Requires hospital initiation for appropriate serum sodium monitoring
• Dosing flexibility with options for titration based on serum sodium response
• Not for use in patients requiring urgent intervention to raise serum sodium

Benefits

• Effectively increases low serum sodium levels in a controlled manner
• Reduces fluid overload symptoms in hypervolemic hyponatremia
• Minimizes risk of overly rapid sodium correction when properly monitored
• Supports management of chronic hyponatremia in appropriate patient populations
• May improve cognitive and physical symptoms associated with hyponatremia
• Provides a targeted alternative to saline infusion in select cases

Common use

Samsca is commonly used in hospitalized patients with euvolemic or hypervolemic hyponatremia, including those with SIADH (due to malignant, pulmonary, or CNS disorders), heart failure, or cirrhosis. It is not indicated for hypovolemic hyponatremia. Treatment should always begin in a hospital setting where serum sodium can be closely monitored due to the risk of overly rapid correction. Use is generally reserved for patients with significant symptoms or those whose hyponatremia is persistent and resistant to fluid restriction.

Dosage and direction

Initiate therapy at 15 mg orally once daily. Dose may be increased to 30 mg once daily, after at least 24 hours, to achieve desired serum sodium level. Maximum daily dose is 60 mg. Administer with or without food. Avoid fluid restriction during the first 24 hours of therapy. Serum sodium, volume, and neurologic status must be monitored frequently (every 6–8 hours initially) during initiation and titration. Duration of treatment should be as short as possible consistent with maintaining serum sodium concentration; avoid use beyond 30 days.

Precautions

Samsca should be used only in patients where the serum sodium can be monitored closely. There is a risk of overly rapid correction of hyponatremia, which can lead to osmotic demyelination syndrome (ODS). Do not use in hypovolemic hyponatremia. Use with caution in patients with renal impairment, hepatic impairment, or those taking strong CYP 3A inhibitors. Dehydration and hypovolemia may occur; monitor fluid balance and vital signs. Not recommended in patients with inability to sense or respond to thirst.

Contraindications

Samsca is contraindicated in patients with hypovolemic hyponatremia, anuria, uncorrected hypernatremia, or history of hypersensitivity to tolvaptan or any component of the product. Concomitant use with strong CYP 3A inhibitors is contraindicated. Do not use in patients who require urgent intervention to raise serum sodium rapidly. Not for use in patients with underlying liver disease (including cirrhosis) unless the benefit outweighs the risk of liver injury.

Possible side effects

Common side effects include thirst, dry mouth, asthenia, constipation, pollakiuria or polyuria, hyperglycemia, and hypernatremia. Serious side effects may include osmotic demyelination (especially with overly rapid correction of sodium), dehydration, hypovolemia, gastrointestinal bleeding in cirrhotic patients, and liver injury. Rare cases of rhabdomyolysis have been reported. Discontinue if signs or symptoms of liver injury occur.

Drug interaction

Strong CYP 3A inhibitors (e.g., ketoconazole, clarithromycin, ritonavir) increase tolvaptan exposure and are contraindicated. Moderate CYP 3A inhibitors (e.g., fluconazole, aprepitant) may also increase exposure; reduce Samsca dose. CYP 3A inducers (e.g., rifampin, phenytoin) may decrease tolvaptan levels. Use with caution with medications that affect serum sodium (e.g., diuretics, NSAIDs, antidepressants) or that may increase risk of bleeding in susceptible patients.

Missed dose

If a dose is missed, take it as soon as possible on the same day. Do not take two doses on the same day to make up for a missed dose. Resume the usual dosing schedule the following day. Patients should be advised not to double the dose.

Overdose

Overdose may lead to profound aquaresis with significant dehydration, hypovolemia, and hypernatremia. Signs and symptoms include excessive thirst, dry mucous membranes, lethargy, weakness, and hypotension. Treatment involves discontinuation of Samsca, careful fluid and electrolyte replacement, and symptomatic support. Hemodialysis is not expected to enhance elimination. Monitor serum sodium and volume status closely.

Storage

Store at 20°–25°C (68°–77°F); excursions permitted between 15°–30°C (59°–86°F). Keep in original container with desiccant; protect from moisture. Keep out of reach of children and pets. Do not use beyond the expiration date printed on the label.

Disclaimer

This information is intended for healthcare professionals. Samsca should be used only under the supervision of a qualified physician familiar with the management of hyponatremia. It is not a substitute for professional medical advice, diagnosis, or treatment. Always follow the approved prescribing information and institutional protocols. Patients must be monitored in a setting where serum sodium can be measured frequently.

Reviews

Clinical trials and post-marketing experience support the efficacy of Samsca in raising serum sodium levels in appropriate patients. In the SALT trials, tolvaptan demonstrated significant improvement in serum sodium compared to placebo over 30 days, with manageable side effects when used according to guidelines. Many clinicians report that it is a useful tool for managing chronic hyponatremia in hospitalized patients, though emphasis remains on careful monitoring to avoid ODS. Long-term use is limited by potential hepatotoxicity and is generally not recommended.