Suxamethonium Chloride is a short-acting depolarizing neuromuscular blocking agent used in anesthesia as a muscle relaxant to:

• Facilitate endotracheal intubation
• Assist in mechanical ventilation
• Provide muscle relaxation during a wide range of surgical and obstetric procedures

Suxamethonium is a depolarizing muscle relaxant that mimics the action of acetylcholine at the neuromuscular junction. It binds to nicotinic receptors on skeletal muscles, causing opening of sodium channels and influx of sodium ions into the muscle cell. This leads to depolarization of the motor end plate and release of calcium from the sarcoplasmic reticulum, resulting initially in muscle fasciculations (brief contractions). Unlike acetylcholine, which is rapidly broken down by acetylcholinesterase, suxamethonium is metabolized more slowly by plasma cholinesterase (butyrylcholinesterase). Because of this slower breakdown, the muscle membrane remains depolarized and cannot respond to further stimulation, leading to muscle relaxation (flaccid paralysis). As calcium is gradually reabsorbed into the sarcoplasmic reticulum, the muscle relaxes completely, explaining the transition from initial fasciculations to flaccidity rather than sustained contraction.

Suxamethonium Chloride is usually administered by bolus Intravenous or Intramuscular injection.

Adults: The dose of Suxamethonium is dependent on body weight, the degree of muscular relaxation required, the route of administration and the response of individual patients. To achieve endotracheal intubation Suxamethonium is usually administered intravenously in a dose of 1 mg/kg. This dose will usually produce muscular relaxation in about 30–60 seconds and has a duration of action of about 2–6 minutes. Supplementary doses of Suxamethonium of 50%–100% of the initial dose administered at 5–10 minutes intervals will maintain muscle relaxation during short surgical procedures performed under general anesthesia. For prolonged surgical procedures Suxamethonium may be given by intravenous infusion as a 0.1%–0.2% solution, diluted in 5% glucose solution or sterile isotonic saline solution, at a rate of 2.5 to 4 mg per minute. The infusion rate should be adjusted according to the response of individual patients. The total dose of Suxamethonium given by repeated intravenous injection or continuous infusion should not be exceeded 500 mg per hour.

Children: Infants and young children are more resistant to Suxamethonium compared with adults. The recommended intravenous dose of Suxamethonium for infants is 2 mg/kg. A dose of 1 mg/kg in older children is recommended. When Suxamethonium is given as intravenous infusion in children, the dosage is as for adults with a proportionately lower initial infusion rate based on body weight. Suxamethonium may be given intramuscularly to infants at doses up to 4–5 mg/kg and in older children up to 4 mg/kg. These doses produce muscular relaxation within about 3 minutes. A total dose of 150 mg should not be exceeded.

Certain medications and chemicals are known to decrease normal plasma cholinesterase activity, which can prolong the neuromuscular blocking action of Suxamethonium. These include trimetaphan; specific anticholinesterase agents such as neostigmine, pyridostigmine, and physostigmine; cytotoxic drugs including cyclophosphamide, mechlorethamine, and triethylene melamine; as well as certain psychiatric medications like promazine and chlorpromazine, and anesthetic or related drugs such as ketamine, morphine and its antagonists, pethidine, and pancuronium.

Suxamethonium does not affect consciousness; therefore, it must not be administered to patients who are not adequately anesthetized. It is contraindicated in individuals with known hypersensitivity to the drug. Suxamethonium is also contraindicated in patients with inherited atypical plasma cholinesterase deficiency. A temporary increase in serum potassium levels (usually about 0.5 mmol/L) commonly occurs after administration in healthy individuals; however, in certain pathological conditions, this increase may be excessive and lead to serious cardiac arrhythmias or cardiac arrest. For this reason, Suxamethonium should not be used in patients recovering from major trauma, those with severe burns, patients with neurological conditions associated with significant muscle wasting, or those with pre-existing hyperkalemia. Suxamethonium may cause a slight and transient increase in intraocular pressure and should therefore be avoided in patients with open eye injuries. This injection is also contraindicated in newborn infants, particularly in premature or immature neonates.

Cardiovascular: bradycardia, tachycardia, hypertension, hypotension, arrhythmias
Respiratory: bronchospasm, prolonged respiratory depression, apnea
Musculoskeletal: muscle fasciculations, postoperative muscle pain, myoglobinemia
Others: hyperthermia, increased intraocular and intragastric pressure, rash, excessive salivation

Suxamethonium does not significantly cross the placenta, but it should be used during pregnancy only if the expected benefit outweighs the potential risks.

Suxamethonium should be administered only by, or under the close supervision of, a trained anesthetist experienced in airway management and artificial ventilation. Adequate facilities for immediate intubation and oxygen administration must be available. Elderly patients may have a higher risk of cardiac arrhythmias, particularly if they are taking digitalis-like medications.

Depolarizing muscle relaxant

Store in a refrigerator at 2°–8°C. Do not freeze.