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V2-Receptor Antagonist (Vasopressin Antagonist)

Tolvaptan

Brand names: Samsca

Used in: Hyponatraemia

Tolvaptan is a selective vasopressin V2-receptor antagonist used for hyponatraemia secondary to the syndrome of inappropriate antidiuretic hormone secretion and, at specialist level, to slow progression in autosomal dominant polycystic kidney disease.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It blocks V2 receptors in the renal collecting ducts, producing electrolyte-free water excretion (aquaresis) and raising serum sodium.

Prescribing in practice

  • Correct serum sodium gradually with close monitoring, as overly rapid correction risks osmotic demyelination syndrome.
  • It carries a risk of clinically significant, potentially fatal liver injury, requiring liver function monitoring particularly in the polycystic kidney disease indication.
  • Ensure access to water and avoid concomitant fluid restriction during initiation to prevent excessive rises in sodium and dehydration.

Monitoring

Monitor serum sodium frequently during initiation and dose changes, and monitor liver function as indicated.

Counselling the patient

  • Drink water in response to thirst and do not restrict fluids unless told to.
  • Report nausea, abdominal pain, dark urine or yellowing of the skin or eyes.
  • Attend for the blood tests arranged to check your sodium and liver.

Evidence & guidelines

The TEMPO 3:4 trial demonstrated that tolvaptan slows kidney function decline in autosomal dominant polycystic kidney disease; UK use is guided by NICE.

Reference: SALT Trials (Schrier et al, NEJM 2006); FDA Drug Safety Communication 2013; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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