Tolvaptan is a medication primarily used to treat hyponatremia (low sodium levels in the blood) associated with conditions such as heart failure, liver cirrhosis, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is a selective vasopressin V2 receptor antagonist, which means it works by blocking the action of vasopressin, a hormone that helps the kidneys manage the body’s water balance. By inhibiting vasopressin, tolvaptan promotes the excretion of water (aquaresis) without significant loss of electrolytes, thereby increasing sodium levels in the blood.
Key Uses:
- Hyponatremia: Tolvaptan is used to raise sodium levels in patients with euvolemic or hypervolemic hyponatremia.
- Autosomal Dominant Polycystic Kidney Disease (ADPKD): It is also approved for slowing kidney function decline in adults at risk of rapidly progressing ADPKD.
Dosage and Administration:
- Hyponatremia: The typical starting dose is 15 mg once daily, which can be increased to 30 mg or 60 mg once daily based on serum sodium levels and tolerability.
- ADPKD: The recommended dose is 45 mg in the morning and 15 mg 8 hours later, with a maximum daily dose of 90 mg.
Side Effects:
Common side effects include:
- Thirst
- Dry mouth
- Frequent urination
- Weakness
- Constipation
- Increased liver enzymes
Serious side effects may include:
- Liver injury
- Rapid correction of sodium levels leading to osmotic demyelination syndrome (ODS)
- Dehydration
Contraindications:
- Patients with anuria (no urine production)
- Hypersensitivity to tolvaptan or any of its components
- Inability to sense or respond to thirst
Monitoring:
- Regular monitoring of serum sodium levels is crucial to avoid rapid correction, which can lead to ODS.
- Liver function tests should be performed before and during treatment, especially in patients with ADPKD.
Special Considerations:
- Pregnancy and Lactation: Tolvaptan should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is not recommended during breastfeeding.
- Elderly: No specific dose adjustment is generally required, but elderly patients may be more susceptible to side effects.
Always consult a healthcare provider for personalized medical advice and before starting or altering any treatment regimen.