V2-Receptor Antagonist (Vasopressin Antagonist) Pregnancy: Avoid — teratogenic in animal studies

Tolvaptan

Brand names: Samsca

Adult dose

Dose: 15 mg OD, may increase to 30 mg OD then 60 mg OD at intervals ≥24h as required

Route: Oral

Frequency: Once daily

Max: 60 mg OD

For hyponatraemia (Na+ <125 mmol/L or symptomatic). Initiate in hospital. Correct Na+ at ≤12 mmol/L/24h to avoid osmotic demyelination.

Paediatric dose

Route: N/A

Frequency: N/A

Max: Not licensed in children

No established paediatric dosing

Dose adjustments

Renal

Caution in renal impairment; not effective if anuria

Hepatic

Contraindicated in patients unable to perceive/respond to thirst. Caution in hepatic impairment — hepatotoxicity reported.

Clinical pearls

SALT-1/SALT-2: effective for SIADH and hypervolaemic hyponatraemia in CHF/cirrhosis
Must initiate in hospital — risk of overcorrection of Na+
Ensure fluid access — patients must be able to drink freely
FDA added hepatotoxicity warning — avoid prolonged use in cirrhosis

Contraindications

Hypovolaemic hyponatraemia
Anuria
Inability to perceive or respond to thirst
Hypernatraemia
Concomitant strong CYP3A4 inhibitors

Side effects

Thirst (very common)
Dry mouth
Polyuria/pollakiuria
Hypernatraemia (overcorrection)
Hepatotoxicity (rare but serious)
Dizziness

Interactions

Strong CYP3A4 inhibitors (ketoconazole) — contraindicated
P-gp inhibitors — increased tolvaptan levels
Digoxin — increased digoxin levels
Hypertonic saline — risk of rapid Na+ rise

Monitoring

Serum sodium (frequently in first 24–48h)
Fluid balance
LFTs (hepatotoxicity monitoring)
Signs of volume depletion

Reference: BNFc; SALT Trials (Schrier et al, NEJM 2006); BNF; FDA Drug Safety Communication 2013. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Myasthenia Gravis Activities of Daily Living (MG-ADL) Scale · Neuromuscular

Pathways