Skeletal muscle relaxant (RyR1 inhibitor)

Dantrolene sodium

Brand names: Dantrium

Adult dose

Dose: Malignant hyperthermia: 2.5mg/kg IV bolus, repeat every 5 min as needed (usual cumulative 10mg/kg, up to 30mg/kg); Spasticity: 25mg PO OD, increase weekly to max 100mg QDS

Route: IV / Oral

Frequency: Per indication

Clinical pearls

AAGBI Malignant Hyperthermia guideline: rapid bolus IV is life-saving — adequate stocks (36 vials, ~2.5mg/kg ×10kg patient) mandatory in operating departments
NICE NG46 spasticity (chronic oral use)
UK MH Investigation Unit (Leeds) — referral for muscle biopsy

Contraindications

Severe hepatic impairment
Pregnancy/breastfeeding
Pulmonary disease (oral, spasticity)
Hypersensitivity

Side effects

Hepatotoxicity (idiosyncratic, fatal — high-dose oral)
Drowsiness
Weakness
Hypersensitivity
Tissue necrosis on extravasation
Hyperkalaemia (rare)
Pleural effusion / pericarditis (chronic oral)

Interactions

Calcium channel blockers (verapamil — hyperkalaemia, cardiovascular collapse)
CNS depressants
Hepatotoxic drugs

Monitoring

Temperature, EtCO2, K+, ABG (acute MH)
LFTs (long-term oral)
Muscle weakness

Reference: BNF; AAGBI MH guideline; NICE NG46; UK MH Investigation Unit; https://bnf.nice.org.uk/drugs/dantrolene-sodium/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators