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 low serum sodium levels by promoting aquaresis—the electrolyte-sparing excretion of free water. By blocking vasopressin binding in the renal collecting ducts, Samsca increases water clearance without significantly affecting sodium or potassium excretion, offering a targeted approach to correcting this potentially serious electrolyte imbalance under careful medical supervision. Its use is reserved for patients whose underlying conditions contribute to inappropriate antidiuretic hormone secretion and requires initiation and re-initiation in a hospital setting to allow for close monitoring of serum sodium and volume status.

Features

• Active ingredient: Tolvaptan
• Pharmacologic class: Selective vasopressin V2-receptor antagonist
• Available as 15 mg and 30 mg tablets
• Mechanism: Promotes aquaresis—excretion of free water
• Requires hospital initiation for serum sodium monitoring
• Not for use in patients requiring urgent intervention to raise serum sodium

Benefits

• Corrects clinically significant hyponatremia by increasing serum sodium concentrations.
• Provides a targeted mechanism of action that promotes free water excretion without substantial loss of electrolytes.
• Can be used in both euvolemic and hypervolemic hyponatremia, including cases associated with heart failure, cirrhosis, and SIADH.
• Oral administration offers a non-invasive treatment option suitable for continued use outside acute care, following initial dose titration.
• Helps alleviate symptoms associated with hyponatremia, such as confusion, headache, and nausea, by restoring sodium balance.
• Supports long-term management of chronic hyponatremia when monitored appropriately.

Common use

Samsca is commonly used in adult patients with hypervolemic or euvolemic hyponatremia. This includes individuals with syndrome of inappropriate antidiuretic hormone secretion (SIADH), heart failure, or cirrhosis, where dilutional or hormonally driven hyponatremia is present. It is not indicated for hypovolemic hyponatremia. Treatment should be initiated and monitored in a hospital environment to rapidly correct sodium levels safely and avoid overly rapid correction, which may lead to osmotic demyelination.

Dosage and direction

Initiate treatment with 15 mg 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. Administration should occur without regard to meals. Fluid restriction during the first 24 hours of therapy is not recommended. Serum sodium, volume, and neurological status must be monitored frequently during initiation and titration. Avoid fluid restriction during active aquaresis.

Precautions

Samsca should be used with caution in patients with renal impairment, as drug exposure may increase. Hepatic impairment is a contraindication. Monitor for signs of dehydration or hypovolemia. Rapid correction of serum sodium (>12 mEq/L/24 hours) can cause serious neurologic sequelae; discontinue or interrupt treatment if sodium rises too rapidly. Not recommended in patients unable to sense or respond to thirst. Avoid use in hypovolemic hyponatremia. Pregnancy and nursing mothers should use only if clearly needed.

Contraindications

Samsca is contraindicated in patients with hypovolemic hyponatremia; in those unable to sense or appropriately respond to thirst; in patients taking strong CYP 3A inhibitors; in anuric patients; and in those with underlying liver disease, including cirrhosis, due to risk of liver injury. It should not be used for urgent sodium correction.

Possible side effect

Common side effects include thirst, dry mouth, asthenia, constipation, pollakiuria or polyuria, hyperglycemia, and hypernatremia. Serious side effects may include overly rapid correction of sodium leading to osmotic demyelination, liver injury, dehydration, and gastrointestinal bleeding in cirrhotic patients. Discontinue if signs of acute liver injury occur.

Drug interaction

Samsca is metabolized by CYP 3A. Strong CYP 3A inhibitors (e.g., ketoconazole, clarithromycin) are contraindicated. Moderate inhibitors (e.g., fluconazole, aprepitant) and P-gp inhibitors may increase tolvaptan exposure. Inducers of CYP 3A (e.g., rifampin, St. John’s wort) may decrease efficacy. Use caution with other medications affecting serum sodium or hydration status.

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 regular dosing schedule the following day.

Overdose

Overdose can lead to profound dehydration, hypernatremia, and hypovolemia. Signs may include excessive thirst, dizziness, syncope, or tachycardia. Treatment involves discontinuation of Samsca, careful water replacement, and symptomatic support. Dialysis is not expected to enhance elimination.

Storage

Store at room temperature (20°C to 25°C); excursions permitted between 15°C and 30°C. Keep in original container with desiccant; protect from moisture. Keep out of reach of children and pets.

Disclaimer

This information is for educational purposes and does not replace professional medical advice. Samsca is a prescription medication and should be used only under the supervision of a qualified healthcare provider. Patients must follow their prescriber’s instructions and report any side effects promptly.

Reviews

Clinical trials and post-marketing experience support the efficacy of Samsca in raising serum sodium levels in appropriate patient populations. In studies, a significant proportion of patients achieved normal sodium levels or a meaningful increase from baseline. Healthcare providers note its utility in managing chronic hyponatremia, though emphasis is placed on the necessity of in-hospital initiation and vigilant monitoring to avoid complications such as rapid sodium correction or liver injury. Patient-reported outcomes often include improvement in hyponatremia-related symptoms following careful dose adjustment.