Dantrolene
Dantrium · Ryanodex
Skeletal muscle ryanodine receptor antagonist
Blocks RYR1 (ryanodine receptor) → ↓ Ca²⁺ release from sarcoplasmic reticulum → muscle relaxation. The only drug for malignant hyperthermia.
Indications
- •Malignant hyperthermia
- •Neuroleptic malignant syndrome (off-label)
- •Spasticity (chronic, oral)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| MH crisis | 2.5 mg/kg IV bolus, repeat q5 min until symptoms resolve (≥ 10 mg/kg often) | Same: 2.5 mg/kg IV |
Pharmacokinetics
Onset 5 min IV. Half-life 4–8 h. Hepatic.
Side effects
- !Muscle weakness (especially with repeat dosing)
- !Hepatotoxicity (chronic oral)
- !Phlebitis (very alkaline; large vein preferred)
- !Mannitol load (3 g per 20 mg vial of original formulation; Ryanodex is mannitol-poor)
Contraindications
- ×None for MH crisis
Clinical pearls
- ★Ryanodex (250 mg/vial, reconstitutes in 5 mL) — fast for MH crisis vs. older 20 mg vial in 60 mL water.
- ★Stock at MH cart in any facility using volatile anesthetics or sux.
- ★Avoid CCBs concurrently — severe hyperkalemia risk.
Education only — confirm against current package inserts and institutional protocols. Doses assume normal organ function unless otherwise noted.