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 facilitates a controlled increase in serum sodium concentrations, thereby mitigating the neurological risks associated with severe hyponatremia. Its use is reserved for patients under close medical supervision to ensure safe and monitored correction.

Features

• Contains tolvaptan, a selective vasopressin V2-receptor antagonist
• Available in 15 mg and 30 mg oral tablets
• Promotes aquaresis without significant electrolyte loss
• Requires initiation in a hospital setting for appropriate monitoring
• Not indicated for hypovolemic hyponatremia

Benefits

• Effectively increases serum sodium levels in appropriate patient populations
• Reduces risk of hyponatremia-related complications such as seizures and altered mental status
• Provides a targeted mechanism of action with minimal impact on key electrolytes like potassium and magnesium
• Supports management of chronic hyponatremia in conjunction with fluid restriction
• May improve patient symptoms related to low sodium, including confusion and fatigue
• Facilitates a controlled rate of sodium correction when administered under supervision

Common use

Samsca is commonly prescribed for adults diagnosed with euvolemic or hypervolemic hyponatremia. Euvolemic hyponatremia often occurs in settings such as SIADH, while hypervolemic hyponatremia is frequently associated with heart failure, cirrhosis, and other conditions involving fluid overload. It is critical that patients are not volume-depleted at the time of initiation. Use is generally limited to short-term treatment, and ongoing assessment of volume status and sodium levels is essential throughout therapy.

Dosage and direction

Initiate therapy with 15 mg taken orally once daily. Dose may be increased to 30 mg once daily after at least 24 hours, if necessary, to achieve desired serum sodium concentration. Do not exceed 60 mg daily. Administration should occur without regard to meals. Patients must be under close medical supervision during initiation and titration to monitor serum sodium and volume status. Fluid restriction is not recommended during the first 24–48 hours of therapy to avoid overly rapid correction.

Precautions

Samsca should be used with caution in patients with renal impairment, as drug exposure may be increased. Hepatic impairment can also affect metabolism and requires careful consideration. Avoid use in patients unable to sense or respond to thirst. Monitor serum potassium in patients at risk for hyperkalemia. Due to the risk of overly rapid correction of hyponatremia, which can lead to osmotic demyelination, frequent monitoring of sodium levels is mandatory—especially during the first 24–48 hours.

Contraindications

Samsca is contraindicated in patients with hypovolemic hyponatremia. Use is also contraindicated in patients unable to sense or respond to thirst, those with anuria, and individuals with a history of hypersensitivity to tolvaptan or any component of the formulation. Concomitant use with strong CYP 3A inhibitors is contraindicated due to increased tolvaptan exposure.

Possible side effects

Common adverse reactions include thirst, dry mouth, asthenia, constipation, pollakiuria or polyuria, and hyperglycemia. Serious side effects may include overly rapid correction of sodium, leading to osmotic demyelination syndrome, hepatic injury, and dehydration. GI bleeding has been reported in cirrhotic patients. Patients should report symptoms such as confusion, headache, nausea, weakness, or difficulty urinating.

Drug interaction

Tolvaptan is a substrate of CYP 3A. Concomitant use with strong CYP 3A inhibitors (e.g., ketoconazole, clarithromycin) is contraindicated. Moderate inhibitors (e.g., fluconazole, aprepitant) may increase tolvaptan exposure—consider dose reduction. Inducers of CYP 3A (e.g., rifampin, St. John’s wort) may decrease tolvaptan levels. Use with other hyperkalemia-inducing drugs may increase risk of hyperkalemia. P-gp inhibitors may also increase tolvaptan concentrations.

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. Patients should be advised not to double the dose.

Overdose

Symptoms of overdose may include pronounced aquaresis, dehydration, and hypernatremia. There is no specific antidote. Treatment should consist of close monitoring of vital signs, fluid and electrolyte balance, and supportive measures. Discontinue Samsca and provide appropriate symptomatic care, which may include free water administration and electrolyte management.

Storage

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

Disclaimer

This information is intended for healthcare professionals and is not a substitute for clinical judgment or professional medical advice. Prescribers should refer to the full prescribing information for complete details regarding indications, dosing, warnings, and precautions. Patients must use Samsca only under the direction of a qualified healthcare provider.

Reviews

Clinical trials and post-marketing experience support the efficacy of Samsca in raising serum sodium levels in indicated patients. Many clinicians report satisfactory correction rates when monitoring protocols are followed. However, the necessity for inpatient initiation and vigilant sodium monitoring is consistently emphasized in expert reviews. Hepatic safety concerns have been noted in long-term studies for other indications, reinforcing the importance of adhering to approved use and duration.