Tolvaptan

1 medicine

Tolvaptan is a vasopressin-receptor blocker used to correct dangerously low blood sodium and slow cyst growth in polycystic kidney disease; it carries a boxed warning for liver injury, and treatment must start in hospital because correcting sodium too quickly can cause serious brain injury.

Samsca

Tolvaptan

15/30mg

Samsca is a hormones medication containing Tolvaptan, available as 15/30mg tablets.

from $5.02 / tablet View

Key facts

  • Tolvaptan is a vasopressin V2-receptor antagonist: it makes the kidneys pass more water without losing sodium, raising blood sodium levels.
  • It is used for hyponatraemia (low blood sodium) from SIADH, heart failure or liver disease, and to slow kidney growth in autosomal dominant polycystic kidney disease (ADPKD).
  • Tolvaptan carries a boxed warning for serious, sometimes fatal liver injury, and treatment for hyponatraemia must be started, and re-started, in hospital, because correcting sodium too fast can cause irreversible brain damage.
  • Seek urgent care for yellowing of the skin or eyes, confusion, seizures, or a rapid change in how alert you feel.

What tolvaptan treats

Tolvaptan treats clinically significant hyponatraemia caused by SIADH, heart failure or cirrhosis, when fluid restriction alone has not worked. A separate, long-term regimen slows the growth of kidney cysts and the decline in kidney function in adults with rapidly progressing ADPKD. It is not a routine diuretic and is not used for ordinary fluid retention or ankle swelling.

How tolvaptan works

Vasopressin normally tells the kidneys to reabsorb water. Tolvaptan blocks the vasopressin V2 receptor in the kidney, so more free water is excreted in the urine while sodium is retained. This dilution effect raises blood sodium concentration. In ADPKD, blocking the same receptor in cyst-lining cells slows fluid-driven cyst growth.

Before you take it

  • Tolvaptan for hyponatraemia is started and dose-adjusted in hospital, with blood sodium checked every few hours at first, because sodium must rise slowly, no more than about 8 to 10 mmol per litre in the first 24 hours.
  • Do not use tolvaptan if you cannot sense or respond to thirst, cannot drink enough fluid when thirsty, or have severe liver disease.
  • Tell your prescriber about any liver problems: tolvaptan is not used beyond the recommended duration in ADPKD because of the liver injury risk, and liver tests are checked before starting and monthly for the first 18 months.
  • Avoid other medicines and grapefruit juice that raise tolvaptan levels unless your prescriber has approved them.

Side effects

Common effects include thirst, dry mouth, frequent urination, constipation and fatigue as your body adjusts to passing more water.

Stop and seek urgent medical care for any of these:

  • Yellowing of the skin or eyes, dark urine, or unusual tiredness.
  • Confusion, difficulty speaking, seizures or worsening drowsiness.
  • Dizziness, fainting or a rapid heartbeat from dehydration.

Safety essentials

  • Tolvaptan carries a boxed warning for serious liver injury; liver tests are mandatory before starting and at regular intervals, and treatment is stopped if levels rise.
  • Sodium correction must be gradual: hyponatraemia treatment is started in hospital with frequent blood tests, because rapid correction can cause permanent brain injury.
  • Drink water when thirsty; do not restrict fluids while taking tolvaptan unless specifically told to.
  • Do not restart tolvaptan after a break without medical supervision; restarting also requires hospital monitoring.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.