Succinylcholine
Anectine · Quelicin
Depolarizing neuromuscular blocker
Acetylcholine receptor agonist at the NMJ; sustained depolarization → fasciculations → flaccid paralysis. Hydrolyzed by plasma cholinesterase.
Indications
- •RSI
- •Laryngospasm rescue
- •ECT (modify motor seizure)
- •Brief paralysis
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| RSI | 1–1.5 mg/kg IV | 2 mg/kg IV (ages 2+); up to 3 mg/kg IV in infants <2 yr; 4 mg/kg IM single dose (max 150 mg) |
| Laryngospasm | 0.1–0.5 mg/kg IV; 4 mg/kg IM if no IV | — |
Pharmacokinetics
Onset 30–60 sec. Duration 5–10 min. Plasma pseudocholinesterase metabolism.
Side effects
- !Hyperkalemia (↑0.5 mEq/L normally; severe in burns > 24 h, denervation, prolonged immobility, MS, ALS, Guillain-Barré)
- !Bradycardia/arrhythmia (especially repeat dose, peds — pretreat with atropine)
- !Masseter rigidity (may herald MH)
- !Postoperative myalgia
- !↑ICP, ↑IOP, ↑intragastric pressure
- !Pseudocholinesterase deficiency → prolonged block (4–8 h vs. 5 min)
- !Anaphylaxis
Contraindications
- ×Personal/family hx malignant hyperthermia
- ×Hyperkalemia
- ×Burns > 24 h, denervation injury, prolonged immobility (upregulated extrajunctional ACh receptors)
- ×Open globe injury (relative)
Reversal / antidote
Wait it out (5–10 min); no pharmacologic reversal. Prolonged block from pseudocholinesterase deficiency: continue ventilation until block resolves (FFP not standard).
Clinical pearls
- ★Always have atropine drawn for peds doses > 0.5 mg/kg.
- ★Phase II block can mimic non-depolarizing block at high cumulative doses.
- ★Defasciculation pretreatment of NDMR ↓ myalgia, ↑ sux dose required by 70%.
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Other drugs in Muscle Relaxants & Reversals
- Rocuronium
Competitive antagonist at the NMJ nicotinic receptor.
- Sugammadex
Encapsulates rocuronium > vecuronium > pancuronium in 1:1 complex. No effect on cisatracurium, atracurium, sux.
- Cisatracurium
Competitive antagonist at the post-synaptic nicotinic ACh receptor at the neuromuscular junction. Single cis-cis isomer of atracurium (4× more potent, lower laudanosine production).
Browse all classes: /reference/drugs