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 imbalance by promoting aquaresis—the electrolyte-sparing excretion of free water. By blocking vasopressin binding in the renal collecting ducts, Samsca increases water clearance without substantial loss of sodium, potassium, or other electrolytes. This mechanism offers a targeted approach to raising serum sodium concentrations in hospitalized patients who require careful monitoring. Appropriate patient selection and strict adherence to dosing protocols are essential to mitigate risks and achieve optimal therapeutic outcomes.

Features

• Contains tolvaptan, a selective vasopressin V2-receptor antagonist
• Available in 15 mg and 30 mg oral tablets
• Promotes aquaresis—electrolyte-sparing free water excretion
• Requires initiation and re-initiation in a hospital setting
• Serum sodium and volume status must be monitored during use
• Not for use in patients with hypovolemic hyponatremia

Benefits

• Effectively increases low serum sodium levels in appropriate patients
• Provides a mechanism for controlled correction of hyponatremia
• Reduces fluid overload symptoms in hypervolemic states
• Minimizes electrolyte disturbances through selective aquaresis
• Supports management of euvolemic hyponatremia, including in SIADH
• May help avoid overly rapid sodium correction when properly monitored

Common use

Samsca is indicated for the treatment of clinically significant hypervolemic and euvolemic hyponatremia, including hyponatremia in patients with heart failure, cirrhosis, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is used in hospitalized patients where serum sodium can be closely monitored due to the need for dose titration and the risk of overly rapid correction. Samsca is not indicated for the treatment of hypovolemic hyponatremia.

Dosage and direction

Initiate and re-initiate therapy in a hospital where serum sodium can be monitored closely. The recommended starting dose is 15 mg administered 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 the desired level of serum sodium. Do not administer for more than 30 days. Fluid restriction during the first 24 hours of therapy may increase the likelihood of overly-rapid correction of serum sodium and should generally be avoided. Take with or without food.

Precautions

Samsca should be used only for hyponatremia that is symptomatic and has resisted correction with fluid restriction. Initiation in a hospital is mandatory due to the need for frequent monitoring of serum sodium and volume status. There is a risk of overly rapid correction of serum sodium, which can cause osmotic demyelination syndrome (ODS), leading to dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma, or death. Patients with malnutrition, alcoholism, or advanced liver disease are at greater risk. Monitor for signs of dehydration and hypovolemia. Monitor liver function tests promptly in patients reporting symptoms that may indicate liver injury.

Contraindications

Samsca is contraindicated in patients with hypovolemic hyponatremia; in patients unable to sense or appropriately respond to thirst; in patients taking strong CYP 3A inhibitors (e.g., ketoconazole, clarithromycin, itraconazole, ritonavir); in patients with anuria; and in patients with a history of a hypersensitivity reaction (e.g., anaphylactic shock, rash) to tolvaptan or any component of the product.

Possible side effects

Common adverse reactions (incidence ≥5% more than placebo) include thirst, dry mouth, asthenia, constipation, pollakiuria or polyuria, and hyperglycemia. Serious side effects include overly rapid correction of serum sodium (risk of ODS), dehydration and hypovolemia, and liver injury. Gastrointestinal bleeding in cirrhotic patients has been reported. Discontinuation due to adverse reactions occurred in 6% of Samsca-treated patients versus 2% of placebo-treated patients.

Drug interaction

Concomitant use with strong CYP 3A inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, ritonavir) is contraindicated due to significant increase in tolvaptan exposure. Moderate CYP 3A inhibitors (e.g., erythromycin, fluconazole, aprepitant, diltiazem, verapamil) can also increase exposure; reduce Samsca dose if co-administered. CYP 3A inducers (e.g., rifampin, rifabutin, St. John’s wort) may decrease tolvaptan exposure; may need dose adjustment. Avoid use with hypertonic saline. P-gp inhibitors may increase tolvaptan concentrations. Monitor patients taking hypertensive medications, as tolvaptan may affect blood pressure.

Missed dose

If a dose is missed, take it as soon as possible on that day. Do not take two doses on the same day. Resume the usual dosing schedule the following day. Do not take extra tablets to make up for a missed dose.

Overdose

Expected manifestations of overdose include signs and symptoms of dehydration and hypovolemia, such as dizziness, hypotension, syncope, tachycardia, and excessive thirst. There is no specific antidote. Treatment involves discontinuation of Samsca, institution of supportive care with careful management of fluid and electrolyte balance, and monitoring of vital signs and serum sodium. AVP and analog administration may be appropriate, but data are limited.

Storage

Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F and 86°F). Keep in original container to protect from moisture. Keep out of reach of children.

Disclaimer

This information is for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Do not disregard professional medical advice or delay in seeking it because of something you have read here. Samsca is a prescription medication and should be used only under the supervision of a healthcare professional.

Reviews

Clinical trials and post-marketing experience support the efficacy of Samsca in raising serum sodium in appropriately selected patients. In pivotal trials, tolvaptan produced a significant increase in serum sodium compared to placebo over 30 days, with a mean change from baseline of approximately 6 mEq/L at day 4 and 8 mEq/L at day 30. Many clinicians note its utility in managing challenging cases of SIADH or heart failure-related hyponatremia, though they emphasize the absolute necessity of in-hospital initiation and vigilant monitoring to prevent ODS. Some reports highlight the challenge of managing thirst as a side effect. Overall, it is regarded as a valuable tool when used judiciously within its strict prescribing framework.