Succinylcholine (Anectine)

• 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

• Generic Name: Succinylcholine chloride (suxamethonium)
• Brand Names: Anectine, Quelicin, various generics

Depolarizing neuromuscular blocker; ultrashort-acting

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

• 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)

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):

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

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

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

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

• 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.