Chemistry:Suxamethonium chloride

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Short description: Chemical compound

Suxamethonium chloride
Clinical data
Pronunciation/ˌsʌksɪnɪlˈkoʊliːn/
Trade namesQuelicin, Anectine, others
AHFS/Drugs.comMonograph
License data
Pregnancy
category
  • AU: A
Routes of
administration		Intravenous, intramuscular
ATC code
Legal status
Legal status
Pharmacokinetic data
BioavailabilityNA
MetabolismBy pseudocholinesterase, to succinylmonocholine and choline
Onset of action30–60 sec (IV), 2–3 min (IM)
Duration of action< 10 min (IV), 10–30 min (IM)
ExcretionKidney (10%)
Identifiers
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
Chemical and physical data
FormulaC14H30Cl2N2O4
Molar mass361.30 g·mol−1
3D model (JSmol)
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Suxamethonium chloride (brand names Scoline and Sucostrin, among others), also known as suxamethonium or succinylcholine, or simply sux in medical abbreviation,[4] is a medication used to cause short-term paralysis as part of the process of general anesthesia.[5] This is done to help with tracheal intubation or electroconvulsive therapy.[5] It is administered by injection, either intravenously or intramuscularly.[6] When used in a vein, onset of action is generally within one minute and effects last for up to 10 minutes.[6]

Common side effects of suxamethonium chloride include low blood pressure, increased saliva production, muscle pain, and rash.[6] Possible serious side effects include malignant hyperthermia, hyperkalemia and allergic reactions.[7][8] The use of suxamethonium chloride is not recommended in the treatment of people who are at risk of hyperkalemia (high blood potassium) or with history of myopathy.[5] Use during pregnancy appears to be safe.[9]

Suxamethonium is a neuromuscular-blocking agent (NMBA), and is classified as a depolarizing neuromuscular drug.[6] It works by blocking the action of acetylcholine on skeletal muscles.[6]

Suxamethonium was described as early as 1906 although it did not enter medical use until 1951.[4] It is on the World Health Organization's List of Essential Medicines.[10] Suxamethonium is a prescription medication in the United States, and is available as a generic medication.[6]

Medical uses

A vial of suxamethonium chloride

Succinylcholine chloride injection is indicated, in addition to general anesthesia, to facilitate tracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation.[8]

Its medical uses are limited to short-term muscle relaxation in anesthesia and intensive care, usually for facilitation of endotracheal intubation. It is popular in emergency medicine due to its rapid onset and brief duration of action. The former is a major point of consideration in the context of trauma care, where endotracheal intubation may need to be completed very quickly (RSI / RSII). The latter means that, should attempts at endotracheal intubation fail and the person cannot be ventilated, there is a prospect for neuromuscular recovery and the onset of spontaneous breathing before low blood oxygen levels occurs. It may be better than rocuronium in people without contraindications due to its faster onset of action and shorter duration of action.[11]

Suxamethonium is also commonly used as the sole muscle relaxant during electroconvulsive therapy, favoured for its short duration of action.[12]

Suxamethonium is quickly degraded by plasma butyrylcholinesterase and the duration of effect is usually in the range of a few minutes. When plasma levels of butyrylcholinesterase are greatly diminished or an atypical form is present (an otherwise harmless inherited disorder), paralysis may last much longer, as is the case in liver failure or in neonates.[13]

The vials are usually stored at a temperature between 2–8 °C, but issues have been reported with lower storage temperatures.[14] The multi-dose vials are stable for up to 14 days at room temperature without significant loss of potency.[3] Unless otherwise indicated in the prescribing information, room temperature for storage of medications is 15–25 °C (59–77 °F).[15]

Side effects

Side effects include malignant hyperthermia, muscle pains, acute rhabdomyolysis with high blood levels of potassium,[13] transient ocular hypertension, constipation[16] and changes in cardiac rhythm, including slow heart rate, and cardiac arrest. In people with neuromuscular disease or burns, an injection of suxamethonium can lead to a large release of potassium from skeletal muscles, potentially resulting in cardiac arrest. Conditions having susceptibility to suxamethonium-induced high blood potassium are burns, closed head injury, acidosis, Guillain–Barré syndrome, cerebral stroke, drowning, severe intra-abdominal sepsis, massive trauma, myopathy, and tetanus.

Suxamethonium does not produce unconsciousness or anesthesia, and its effects may cause considerable psychological distress while simultaneously making it impossible for a patient to communicate. Therefore, administration of the drug to a conscious patient is contraindicated.

Hyperkalemia

The side effect of high blood potassium may occur because the acetylcholine receptor is propped open, allowing continued flow of potassium ions into the extracellular fluid. A typical increase of potassium ion serum concentration on administration of suxamethonium is 0.5 mmol per liter.The increase is transient in otherwise healthy patients. The normal range of potassium is 3.5 to 5 mEq per liter. High blood potassium does not generally result in adverse effects below a concentration of 6.5 to 7 mEq per liter. Therefore, the increase in serum potassium level is usually not catastrophic in otherwise healthy patients. Severely high blood levels of potassium can cause changes in cardiac electrophysiology, which, if severe, can result in arrhythmias and even cardiac arrest.[17][18]

Malignant hyperthermia

See also: Medicine:Malignant hyperthermia

Administering suxamethonium and certain other anesthetics can result in a drastic and uncontrolled increase in skeletal muscle oxidative metabolism. This overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature, eventually leading to circulatory collapse and death if not treated quickly.

Susceptibility to malignant hyperthermia is often inherited as an autosomal dominant disorder, for which there are at least six genetic loci of interest, the most prominent being the ryanodine receptor gene (RYR1). MH susceptibility is phenotype and genetically related to central core disease (CCD), an autosomal dominant disorder characterized both by MH symptoms and by myopathy. MH is usually unmasked by anesthesia, or when a family member develops the symptoms. There is no simple, straightforward test to diagnose the condition. When MH develops during a procedure, treatment with dantrolene sodium is usually initiated; dantrolene and the avoidance of suxamethonium administration in susceptible people have markedly reduced the mortality from this condition.[19]

Apnea

See also: Medicine:Pseudocholinesterase deficiency

The normal short duration of action of suxamethonium is due to the rapid metabolism of the drug by non-specific plasma cholinesterases. However, plasma cholinesterase activity is reduced in some people due to either genetic variation or acquired conditions, which results in a prolonged duration of neuromuscular block. Genetically, ninety six percent of the population have a normal (Eu:Eu) genotype and block duration; however, some people have atypical genes (Ea, Es, Ef) which can be found in varying combinations with the Eu gene, or other atypical genes (see Pseudocholinesterase deficiency). Such genes will result in a longer duration of action of the drug, ranging from 20 minutes up to several hours. Acquired factors that affect plasma cholinesterase activity include pregnancy, liver disease, kidney failure, heart failure, thyrotoxicosis, and cancer, as well as a number of other drugs.[20]

If unrecognized by a clinician it could lead to awareness if anesthesia is discontinued whilst still paralyzed or hypoxemia (and potentially fatal consequences) if artificial ventilation is not maintained. Normal treatment is to maintain sedation and ventilate the patient in an intensive care unit until muscle function has returned. Blood testing for cholinesterase function can be performed.[21]

Mivacurium, a non-depolarizing neuromuscular blocking drug, is also metabolized via the same route with a similar clinical effect in patients deficient in plasma cholinesterase activity.[22]

Deliberate induction of conscious apnea using this drug led to its use as a form of aversion therapy in the 1960s and 1970s in some prison and institutional settings.[23][24][25] This use was discontinued after negative publicity concerning the terrifying effects on subjects of this treatment and ethical questions about the punitive use of painful aversion.

Mechanism of action

There are two phases to the blocking effect of suxamethonium.

Phase 1 block

Phase 1 blocking has the principal paralytic effect. Binding of suxamethonium to the nicotinic acetylcholine receptor results in opening of the receptor's ion channel; a depolarization of the motor end-plate occurs and calcium is released from the sarcoplasmic reticulum leading to initial muscle contraction and fasciculations.[26]

In normal skeletal muscle, acetylcholine dissociates from the receptor following depolarization and is rapidly hydrolyzed by acetylcholinesterase. The muscle cell is then ready for the next signal.[26]

Suxamethonium is not hydrolyzed by acetylcholinesterase. By remaining bound to the acetylcholine receptor and maintaining the membrane potential above threshold, it does not allow the muscle cell to completely repolarize. This results in the inability for the voltage gated sodium channels to reset and instead are held in an inactive state leading to an inability to form further action potentials.[26]

Voltage gated calcium channels likely close as the partially depolarised membrane potential remains between -30mV and -60mV, which is below the opening of the voltage gated calcium channel, approximately -10mV. Subsequently calcium is removed from the muscle cell cytoplasm . As the calcium is taken up by the sarcoplasmic reticulum, the muscle relaxes resulting in muscle flaccidity.[27][28]

The results are membrane depolarization and transient fasciculations, followed by flaccid paralysis.

Phase 2 block

While this phase is not abnormal and is a part of its mechanism of action, it is undesirable during surgery , due to the inability to depolarize the cell again.[26] Often, patients must be on a ventilator for hours if Phase 2 block occurs.[citation needed]

References

  1. ↑ "Product monograph brand safety updates". February 2024. https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-product-database/label-safety-assessment-update/product-monograph-brand-safety-updates.html. 
  2. ↑ "Anectine- succinylcholine chloride injection, solution". DailyMed. U.S. National Library of Medicine. 17 September 2018. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a1e5d29f-111e-4a44-addf-beeb6ea81711. 
  3. ↑ 3.0 3.1 "Quelicin- succinylcholine chloride injection, solution". DailyMed. U.S. National Library of Medicine. 15 February 2019. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=fb08161e-7711-406d-e7b3-ea4515c07983. 
  4. ↑ 4.0 4.1 "Clinical implications of new neuromuscular concepts and agents: so long, neostigmine! So long, sux!". Journal of Critical Care 24 (1): 43–49. March 2009. doi:10.1016/j.jcrc.2008.08.009. PMID 19272538. 
  5. ↑ 5.0 5.1 5.2 WHO Model Formulary 2008. World Health Organization. 2009. pp. 426–8. ISBN 978-92-4-154765-9. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 "Succinylcholine Chloride". The American Society of Health-System Pharmacists. https://www.drugs.com/monograph/succinylcholine-chloride.html. 
  7. ↑ "Anectine Injection - Summary of Product Characteristics (SPC) - (eMC)". 12 January 2016. https://www.medicines.org.uk/emc/medicine/704. 
  8. ↑ 8.0 8.1 "Coronavirus (COVID-19) Update: December 22, 2020". U.S. Food and Drug Administration (Press release). 22 December 2020. Retrieved 23 December 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  9. ↑ "Prescribing medicines in pregnancy database" (in en). 3 January 2026. https://www.tga.gov.au/prescribing-medicines-pregnancy-database. 
  10. ↑ World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. 2019. WHO/MVP/EMP/IAU/2019.06.. 
  11. ↑ "Rocuronium versus succinylcholine for rapid sequence induction intubation". The Cochrane Database of Systematic Reviews 2015 (10). October 2015. doi:10.1002/14651858.CD002788.pub3. PMID 26512948. 
  12. ↑ "Goodbye suxamethonium!". Anaesthesia 64 (Suppl 1): 73–81. March 2009. doi:10.1111/j.1365-2044.2008.05873.x. PMID 19222434. 
  13. ↑ 13.0 13.1 Rang and Dale's Pharmacology (7th ed.). Elsevier Science Health Science Division. 25 March 2011. ISBN 978-0-7020-3471-8. https://books.google.com/books?id=6Go5RQAACAAJ. 
  14. ↑ "Frozen succinylcholine: the danger of being overzealous with its cold storage". Br J Anaesth 116 (2): 299–300. February 2016. doi:10.1093/bja/aev465. PMID 26787804. 
  15. ↑ "Guidelines for the Storage of Essential Medicines and Other Health Commodities: 3. Maintaining the Quality of Your Products: Controlling temperature". World Health Organization. https://apps.who.int/medicinedocs/en/d/Js4885e/6.5.html. 
  16. ↑ Matzke Pharmacotherapy: A Pathophysiologicḣ Approach (6th ed.). McGraw-Hill. 2005. p. 685. 
  17. ↑ "Succinylcholine Chloride". StatPearls. 2022. https://www.ncbi.nlm.nih.gov/books/NBK499984/. 
  18. ↑ "Succinylcholine-induced hyperkalemia in acquired pathologic states: etiologic factors and molecular mechanisms". Anesthesiology 104 (1): 158–169. January 2006. doi:10.1097/00000542-200601000-00022. PMID 16394702. 
  19. ↑ "Malignant hyperthermia: MedlinePlus Genetics" (in en). https://medlineplus.gov/genetics/condition/malignant-hyperthermia/. 
  20. ↑ Pharmacology for Anaesthesia and Intensive Care (2nd ed.). London, UK: Greenwich Medical Media Limited. 2003. ISBN 1-84110-166-4. 
  21. ↑ "A test to evaluate preoperative patients for succinylcholine (suxamethonium) anesthetic sensitivity.". https://www.labcorp.com/tests/007211/cholinesterase. 
  22. ↑ "Pharmacodynamics of mivacurium chloride in 13- to 18-yr-old adolescents with thermal injury". British Journal of Anaesthesia 89 (4): 580–585. October 2002. doi:10.1093/bja/aef234. PMID 12393359. 
  23. ↑ "Succinylcholine as a modifier of acting-out behavior". Clinical Medicine 77 (7): 28. 1970. 
  24. ↑ "A Bit of 'Clockwork Orange,' California-Style". Washington Post. 5 April 1972. https://news.google.com/newspapers?nid=1755&dat=19720408&id=rLkqAAAAIBAJ&pg=7180%2C2668925. 
  25. ↑ The Punishment Cure. New York: Mason/Charter. 1975. ISBN 0-88405-118-8. 
  26. ↑ 26.0 26.1 26.2 26.3 "Pharmacology of neuromuscular blocking drugs.". Continuing Education in Anaesthesia Critical Care & Pain 4 (1): 2–7. February 2004. doi:10.1093/bjaceaccp/mkh002. 
  27. ↑ "CaV1.1 voltage-sensing domain III exclusively controls skeletal muscle excitation-contraction coupling". Nature Communications 15 (1). August 2024. doi:10.1038/s41467-024-51809-5. PMID 39198449. Bibcode: 2024NatCo..15.7440P. 
  28. ↑ "Succinylcholine and decamethonium: comparison of depolarization and desensitization" (in en-US). Anesthesiology 33 (6): 611–618. December 1970. doi:10.1097/00000542-197012000-00007. PMID 5477644. 



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