SUCCINYLCHOLINE CHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SUCCINYLCHOLINE CHLORIDE (SUCCINYLCHOLINE CHLORIDE).
Depolarizing neuromuscular blocker that binds to nicotinic acetylcholine receptors at the motor endplate, causing initial depolarization followed by sustained membrane depolarization and desensitization, leading to muscle paralysis.
| Metabolism | Hydrolyzed by plasma pseudocholinesterase (butyrylcholinesterase) into succinylmonocholine and choline; minimal hepatic metabolism. |
| Excretion | Succinylcholine is rapidly hydrolyzed by plasma pseudocholinesterase. Only 2-10% of the administered dose is excreted unchanged in the urine; the remainder is metabolized to succinylmonocholine and further to succinic acid and choline. Biliary/fecal elimination is negligible. |
| Half-life | The terminal elimination half-life of succinylcholine is approximately 2–4 minutes in patients with normal pseudocholinesterase activity. Clinically, this short half-life correlates with rapid offset of neuromuscular blockade. In patients with atypical or deficient pseudocholinesterase, half-life may be prolonged to 20–60 minutes or more. |
| Protein binding | Succinylcholine is approximately 30% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 0.3–0.6 L/kg. This low Vd reflects limited distribution into total body water and minimal tissue binding. It is consistent with a highly polar, quaternary ammonium compound that does not readily cross cell membranes. |
| Bioavailability | Oral bioavailability is negligible (<5%) due to rapid hydrolysis in the gastrointestinal tract and first-pass metabolism. Intramuscular administration yields nearly 100% bioavailability as the drug is rapidly absorbed into the systemic circulation. |
| Onset of Action | Intravenous (IV): Onset of neuromuscular blockade occurs within 30–60 seconds, with maximal effect at 1 minute. Intramuscular (IM): Onset is 2–3 minutes. Intraosseous (IO): Similar to IV. |
| Duration of Action | IV administration produces neuromuscular blockade lasting approximately 5–10 minutes for a typical intubating dose (1–1.5 mg/kg). Duration is dose-dependent and prolonged with repeated doses or continuous infusion. Recovery is generally complete within 10–12 minutes. In patients with pseudocholinesterase deficiency, duration may extend to several hours. |
| Action Class | Skeletal muscle relaxant- Peripherally acting |
1-1.5 mg/kg IV bolus for intubation; 2.5-4 mg/kg IM if IV access unavailable.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for GFR >10 mL/min. For GFR <10 mL/min, use with caution due to risk of hyperkalemia; no dose reduction recommended. |
| Liver impairment | No dose adjustment required for Child-Pugh A or B. For Child-Pugh C, use with caution; consider dose reduction by 50% due to prolonged duration of action. |
| Pediatric use | Infants and children: 2 mg/kg IV for intubation; 3-4 mg/kg IM. Neonates: 2 mg/kg IV. |
| Geriatric use | Use lower end of dosing range (e.g., 0.6 mg/kg IV) due to decreased plasma cholinesterase activity and increased risk of prolonged blockade. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SUCCINYLCHOLINE CHLORIDE (SUCCINYLCHOLINE CHLORIDE).
| Breastfeeding | Succinylcholine is rapidly metabolized and has a very short half-life (2-4 minutes). It is not expected to be excreted into breast milk in clinically significant amounts due to its rapid degradation and low lipid solubility. No M/P ratio has been reported. Considered compatible with breastfeeding. However, caution is advised in mothers with atypical pseudocholinesterase due to potential prolonged action. |
| Teratogenic Risk | Succinylcholine chloride is a quaternary ammonium compound that does not cross the placental barrier in significant amounts due to its high polarity and rapid hydrolysis by plasma pseudocholinesterase. Animal studies have not shown teratogenic effects. However, use during pregnancy should be reserved for essential indications such as cesarean section or emergency intubation. Theoretical risk of fetal neuromuscular blockade exists if large doses are administered, but clinical data are limited. No specific trimester-specific risks have been established; the drug is considered low risk when used in standard doses. |
■ FDA Black Box Warning
Risk of cardiac arrest from hyperkalemia in patients with undiagnosed skeletal muscle myopathies, especially in children. Malignant hyperthermia has been reported.
| Serious Effects |
["Known hypersensitivity to succinylcholine","Personal or family history of malignant hyperthermia","Skeletal muscle myopathies (e.g., Duchenne muscular dystrophy)","Plasma pseudocholinesterase deficiency or genetic variants","Acute phase of major burns, trauma, or spinal cord injury (risk of hyperkalemia)","Glaucoma or penetrating eye injury (caution)"]
| Precautions | ["Risk of hyperkalemia leading to cardiac arrest in patients with significant muscle injury, denervation, or myopathy","Malignant hyperthermia risk","Prolonged apnea in patients with pseudocholinesterase deficiency","Increased intraocular and intragastric pressure","Bradycardia, especially with repeat doses"] |
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| Fetal Monitoring | Monitor maternal vital signs (heart rate, blood pressure, oxygen saturation), neuromuscular function via peripheral nerve stimulator (train-of-four monitoring), and signs of malignant hyperthermia (tachycardia, hypercapnia, muscle rigidity). Fetal heart rate monitoring is recommended if used during cesarean section or maternal surgery. Continuous ECG and ETCO2 monitoring are essential. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. Succinylcholine is a depolarizing neuromuscular blocker with no hormonal or gonadal effects. Its short duration of action precludes long-term reproductive impact. |