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Bedside Snapshot
  • Core Use: Rapid sequence intubation (RSI) when no contraindications present; advantages include very rapid onset (~30–60 seconds) and short duration (~5–10 minutes)
  • Standard Adult RSI Dose: 1–1.5 mg/kg IV based on total body weight
  • Onset/Duration: Onset 30–60 seconds; duration 5–10 minutes (rapidly metabolized by plasma cholinesterase)
  • Key Dangers: Life-threatening hyperkalemia in susceptible patients (burns, crush injuries, neuromuscular disease, prolonged immobilization, denervation); trigger for malignant hyperthermia (MH)
  • Special Note: Provides NO sedation, amnesia, or analgesia—ensure adequate induction agent and post-intubation sedation/analgesia. Many ED/ICU practices favor rocuronium as first-line RSI paralytic due to safety concerns
Brand & Generic Names
  • Generic Name: Succinylcholine chloride (suxamethonium)
  • Brand Names: Anectine, Quelicin, various generics
Medication Class

Depolarizing neuromuscular blocker; ultrashort-acting

Pharmacology

Mechanism of Action:

  • Depolarizing neuromuscular blocker composed of two acetylcholine molecules linked together
  • Binds to nicotinic acetylcholine receptors at the neuromuscular junction, causing persistent depolarization of the motor endplate (phase I block)
  • Initial depolarization leads to fasciculations, followed by flaccid paralysis as the endplate cannot repolarize while succinylcholine remains bound
  • Rapidly hydrolyzed by plasma pseudocholinesterase, so depolarization is brief and neuromuscular transmission resumes
  • With large doses, prolonged infusions, or certain pathologic states, a phase II block resembling nondepolarizing blockade can occur

Pharmacokinetics:

  • Onset: 30–60 seconds after IV bolus at 1–1.5 mg/kg; maximal paralysis usually within 1 minute
  • Duration: 5–10 minutes after a single standard dose in patients with normal pseudocholinesterase activity
  • Distribution: Small volume of distribution (~0.2–0.4 L/kg); does not cross the blood–brain barrier
  • Metabolism: Rapid hydrolysis by plasma pseudocholinesterase (butyrylcholinesterase) to succinylmonocholine and choline
  • Elimination: Metabolites excreted in urine; duration markedly prolonged in patients with pseudocholinesterase deficiency, severe liver disease, pregnancy, or after exposure to certain drugs/organophosphates
Indications
  • Rapid sequence intubation (RSI) in adult and pediatric patients when succinylcholine is not contraindicated and a depolarizing agent is preferred for its rapid onset and short duration
  • Facilitation of short procedures requiring profound but brief neuromuscular blockade in controlled settings (usually anesthesia-managed)
  • Occasionally used in electroconvulsive therapy (ECT) to minimize motor activity (OR/psychiatry setting)
Dosing & Administration

Available Forms:

  • IV solution: commonly supplied as 20 mg/mL (e.g., 100 mg/5 mL vial) or 10 mg/mL in multi-dose vials
  • Stable when refrigerated; may have limited room-temperature stability depending on formulation and manufacturer
  • For RSI, succinylcholine is typically given as a rapid IV push; IM dosing is slower and generally reserved for specific circumstances (e.g., no IV access in perioperative settings)

Dosing – Succinylcholine (ED/ICU RSI; always follow local protocol):

Indication / Population Dose Onset / Duration Notes
Adult RSI (standard) 1–1.5 mg/kg IV (total body weight) Onset 30–60 s; duration 5–10 min Most common ED/ICU dosing; lower doses risk incomplete paralysis
Adult RSI (hemodynamic fragility) 0.5–1.0 mg/kg IV Onset may be slower; duration shorter Consider only when risk/benefit favors faster recovery over guaranteed deep paralysis
Pediatric RSI (IV) 1–2 mg/kg IV (total body weight) Onset 30–60 s; duration 5–10 min Use with caution; black box warning due to risk of hyperkalemic arrest in undiagnosed myopathies
IM dosing (perioperative) 3–4 mg/kg IM (max ~150 mg) Onset 2–3 min; duration similar Used when IV access not available; slower and less predictable
Repeat dosing 0.5–1 mg/kg IV Time to recovery shortens with each dose Repeat doses increase risk of bradycardia (especially in children) and hyperkalemia
Pseudocholinesterase deficiency Avoid or use extreme caution Paralysis may last >30–60 min Consider nondepolarizing NMB instead; anticipate need for prolonged ventilation if given
Contraindications

Absolute/Strong Contraindications:

  • Known or suspected susceptibility to malignant hyperthermia or personal/family history of MH with volatile anesthetics or succinylcholine
  • History of succinylcholine-induced hyperkalemic cardiac arrest or severe hyperkalemia
  • Significant hyperkalemia from any cause at baseline (e.g., ESRD with markedly elevated K⁺)
  • Major burns >24–48 hours old (risk of upregulated extrajunctional receptors and massive K⁺ release)
  • Crush injury, severe muscle trauma, spinal cord injury, or stroke with denervation or prolonged immobility (>48–72 hours)
  • Known or suspected neuromuscular diseases (e.g., muscular dystrophies, motor neuron disease, Guillain–Barré, ALS)
  • Known or suspected pseudocholinesterase deficiency (congenital or acquired)

Relative Contraindications / Cautions:

  • Pediatric patients: Particularly boys with undiagnosed Duchenne muscular dystrophy; black box warning for routine elective use in children due to risk of rhabdomyolysis and hyperkalemic arrest
  • Pre-existing or high-risk conditions for hyperkalemia (e.g., severe sepsis, prolonged ICU stay, muscle wasting) even without obvious denervation
  • Increased intracranial, intraocular, and intragastric pressure: succinylcholine can transiently increase these; weigh risks vs benefits in head injury, ocular trauma, or recent eye surgery
  • Bradycardia risk, especially in children and with repeat dosing; consider pretreatment with atropine in pediatrics when appropriate
  • Patients with severe hepatic disease, pregnancy, or exposure to organophosphate inhibitors may have reduced pseudocholinesterase activity and prolonged paralysis
Adverse Effects

Common:

  • Transient muscle fasciculations and postoperative myalgias
  • Mild hyperkalemia in otherwise healthy patients (usually small increase)
  • Transient increases in intraocular, intracranial, and intragastric pressure
  • Bradycardia or tachycardia; bradycardia more common in children or with repeat doses

Serious:

  • Severe hyperkalemic cardiac arrest in susceptible patients (burns, crush, denervation, myopathies, severe hyperK, etc.)
  • Malignant hyperthermia when combined with volatile anesthetics in susceptible individuals (hypercapnia, rigidity, hyperthermia, acidosis, rhabdomyolysis)
  • Prolonged apnea and paralysis in patients with pseudocholinesterase deficiency or enzyme inhibition
  • Masseter muscle rigidity that may herald malignant hyperthermia in some patients
  • Anaphylaxis and severe hypersensitivity reactions
Special Populations

Pediatric:

  • Black box warning: Risk of hyperkalemic cardiac arrest in children with undiagnosed muscular dystrophies (especially Duchenne)
  • Consider rocuronium as first-line paralytic in pediatric RSI
  • If succinylcholine used: dose 1–2 mg/kg IV; higher risk of bradycardia (consider atropine pretreatment)

Pregnancy & Lactation:

  • Pregnancy may reduce pseudocholinesterase activity, potentially prolonging paralysis
  • May be used when clinically indicated for RSI in pregnancy; ensure adequate post-intubation sedation/analgesia

Renal Impairment:

  • Patients with ESRD or severe hyperkalemia at baseline should NOT receive succinylcholine
  • Use rocuronium or other nondepolarizing NMB instead

Hepatic Impairment:

  • Severe liver disease may reduce pseudocholinesterase production, prolonging paralysis
  • Be prepared for prolonged ventilatory support if succinylcholine used
Monitoring

Clinical Monitoring:

  • Continuous ECG, blood pressure, and pulse oximetry during RSI and immediate post-intubation period
  • Capnography and ventilator parameters to confirm adequate ventilation and endotracheal tube placement
  • Close observation for return of neuromuscular function (spontaneous respirations, movement) after expected duration
  • Delayed recovery should prompt consideration of pseudocholinesterase deficiency or drug interactions

Laboratory Monitoring:

  • Serum potassium and other electrolytes in high-risk patients or after cardiac arrest following succinylcholine use
  • For patients in whom MH is suspected: monitor ETCO₂, core temperature, rigidity, CK, potassium, and acid–base status; initiate MH protocol and dantrolene if indicated
Clinical Pearls
Fast On/Fast Off: Think of succinylcholine as the "fast on/fast off" paralytic—great when you are confident you can bag the patient but might fail intubation; dangerous when they are at high risk for hyperkalemia or MH.
Screen Before Use: Before using succinylcholine, quickly screen for burns, crush injury, neuromuscular disease, prolonged immobilization, ESRD with high K⁺, and personal/family history of MH.
Rocuronium Alternative: Rocuronium at 1.2 mg/kg IV provides comparable onset without the hyperkalemia and MH risk but at the cost of a much longer duration of paralysis—many ED/ICU teams now default to rocuronium for this reason.
Fasciculations Normal: Fasciculations and post-intubation myalgias are common but usually self-limited; pretreatment with small doses of nondepolarizing NMBs is rarely used in modern ED practice.
No Awareness Under Paralysis: Regardless of which paralytic you choose, have your post-intubation sedation and analgesia plan in place before you push the NMB to avoid awareness under paralysis.
References
  • 1. Lexicomp. (2025). Succinylcholine: Drug information. Wolters Kluwer.
  • 2. Rosenberg, H., Pollock, N., Schiemann, A., Bulger, T., & Stowell, K. (2015). Malignant hyperthermia: A review. Orphanet Journal of Rare Diseases, 10, 93.
  • 3. Naguib, M., & Brull, S. J. (2018). Neuromuscular blocking agents and reversal agents. In Miller's Anesthesia (9th ed.). Elsevier.
  • 4. Drake, M. G. (2017). Neuromuscular blockade for emergency airway management. Annals of Translational Medicine, 5(17), 355.
  • 5. Farkas, J. (2024). Rapid sequence intubation (RSI) and delayed sequence intubation (DSI) (IBCC). EMCrit Project.
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