Samsca (tolvaptan) is an oral 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 selectively blocking vasopressin binding in the renal collecting ducts, Samsca promotes aquaresis—the excretion of free water—without significant loss of electrolytes, facilitating a controlled increase in serum sodium concentration. Its use requires careful monitoring under medical supervision to ensure safe and gradual correction, reducing the risk of osmotic demyelination syndrome.

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 initiation and dose titration in a hospital setting
• FDA-approved for hypervolemic and euvolemic hyponatremia
• Not indicated for hypovolemic hyponatremia

Benefits

• Increases serum sodium levels in a controlled manner, reducing neurological risks associated with hyponatremia
• Provides a targeted mechanism of action, minimizing unnecessary electrolyte loss
• Supports management of chronic hyponatremia in outpatient settings after initial titration
• May improve cognitive and physical symptoms related to low sodium levels
• Reduces fluid overload in hypervolemic patients without diuretic-induced electrolyte depletion
• Offers oral administration convenience compared to intravenous alternatives

Common use

Samsca is commonly prescribed for adult patients with clinically significant hypervolemic or euvolemic hyponatremia. This includes individuals with heart failure, liver cirrhosis, or the syndrome of inappropriate antidiuretic hormone (SIADH). It is particularly valuable in cases where hyponatremia is symptomatic or persistent despite fluid restriction. Treatment is typically initiated in a hospital or closely monitored clinical environment to allow for frequent serum sodium assessments and dose adjustments. Samsca is not intended for emergency correction of acute hyponatremia or for use in patients requiring urgent intervention to prevent serious neurological symptoms.

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 a maximum of 60 mg once daily, as needed to achieve desired serum sodium levels. Administer with or without food. Avoid fluid restriction during the first 24 hours of therapy. Frequent monitoring of serum sodium and volume status is essential during initiation and titration. Treatment duration should be limited to 30 days due to potential risk of liver injury. Discontinue Samsca if serum sodium fails to rise appropriately or if overly rapid correction occurs.

Precautions

Monitor serum sodium concentrations and neurologic status closely during initiation and titration due to risk of overly rapid correction. Avoid use in hypovolemic hyponatremia; correct volume depletion prior to initiation. Use with caution in patients with renal impairment or hepatic disease. Samsca may cause dehydration and hypovolemia; ensure patients have access to water and can drink appropriately. Not recommended for use in patients with inability to sense or respond to thirst. Discontinue therapy if significant liver enzyme abnormalities occur.

Contraindications

Samsca is contraindicated in patients with hypovolemic hyponatremia, concomitant use of strong CYP 3A inhibitors, anuria, inability to sense or respond to thirst, and in patients with urgent need to raise serum sodium acutely. It should not be used in patients with known hypersensitivity to tolvaptan or any component of the product.

Possible side effects

Common adverse reactions (incidence ≥5% and greater than placebo) 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, hepatic injury, GI bleeding in cirrhotic patients, and dehydration. Discontinuation may be necessary if significant adverse effects occur.

Drug interaction

Strong CYP3A inhibitors (e.g., ketoconazole, clarithromycin) significantly increase tolvaptan exposure and are contraindicated. Moderate CYP3A inhibitors (e.g., fluconazole) may increase exposure; reduce Samsca dose. P-gp inhibitors may increase concentrations. Avoid concomitant use with hypertonic saline. Use caution with other medications affecting serum sodium or volume status.

Missed dose

If a dose is missed, skip the missed dose and resume the usual dosing schedule the next day. Do not double the dose to make up for a missed administration. Patients should be advised to maintain consistent daily dosing and inform their healthcare provider of any missed doses, particularly during the titration phase.

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. Discontinue Samsca and provide supportive care, including water ingestion and IV fluids if needed. Monitor serum sodium and vital signs closely. There is no specific antidote; treatment should focus on correction of fluid and electrolyte imbalances.

Storage

Store at room temperature (20–25°C or 68–77°F); excursions permitted between 15–30°C (59–86°F). Keep in original container with desiccant to protect from moisture. Keep out of reach of children and pets. Do not use if the blister pack is damaged or tablets show signs of deterioration.

Disclaimer

This information is intended for healthcare professionals. Samsca should be used only under appropriate medical supervision with regular monitoring. Patients must be advised regarding the risks and benefits of therapy. This is not exhaustive clinical information; please refer to the full prescribing information for complete details regarding use, warnings, and precautions.

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 within 7–14 days of treatment. Healthcare providers report that careful patient selection and monitoring are essential for optimal outcomes. Some note challenges with long-term use due to the 30-day limitation and potential hepatic concerns. Overall, it is regarded as a valuable option for specific cases of hyponatremia when used according to guidelines.