Succinylcholine

Succinylcholine chloride injection is a fast-acting muscle relaxant used in hospitals and operating rooms for specific, short-term purposes.

• As an adjunct to general anesthesia — to support the anesthetic process by relaxing muscles
• To facilitate tracheal intubation — to relax the muscles of the throat and airway so a breathing tube can be placed quickly and safely
• To provide skeletal muscle relaxation during surgery or mechanical ventilation
• Anectine and Quelicin carry the same set of approved uses as other succinylcholine chloride injection products — all are indicated in both adults and pediatric patients for the above purposes
• In children, use is reserved for emergency airway situations (such as laryngospasm, difficult airway, or full stomach) or when no vein is accessible for intravenous access

Succinylcholine is a depolarizing neuromuscular blocker. It mimics acetylcholine — the body's own nerve-to-muscle messenger — by binding to the same receptors at the neuromuscular junction (the connection point between a nerve and a muscle). This initial binding causes a brief burst of muscle activity seen as small involuntary twitches called fasciculations. After that initial trigger, the receptors stay occupied and the muscle cannot respond to any further nerve signals, resulting in complete, temporary muscle relaxation (flaccid paralysis). After an intravenous dose, onset is typically less than one minute and the effect lasts roughly 4 to 6 minutes with a single dose.

With repeated or prolonged dosing, the nature of the block can shift from the typical depolarizing type (Phase I) to one that behaves more like a non-depolarizing block (Phase II), which may cause prolonged muscle weakness or paralysis and requires careful monitoring to manage safely.

Succinylcholine is given only by injection — intravenously (into a vein) or intramuscularly (into a muscle) — by trained healthcare professionals in a clinical setting. It is never self-administered at home.

• The dose is individualized for every patient based on careful assessment — there is no standard one-size dose
• It is administered and monitored by experienced clinicians using neuromuscular monitoring equipment
• It should only be given where equipment and staff for emergency airway management and resuscitation are immediately available
• Only clear, colorless solutions should be used; the solution should be checked visually before administration

Like all powerful anesthetic medications, succinylcholine can cause a range of side effects, from mild and expected to serious and requiring immediate action.

• Muscle twitching (fasciculations) immediately after injection
• Muscle soreness or pain after the procedure
• Slow heart rate (bradycardia) — more common in children and with repeated doses
• Fast heart rate (tachycardia)
• High or low blood pressure
• Increased saliva production
• Increased pressure inside the eyes (intraocular pressure)
• Skin rash or flushing

Serious reactions — including cardiac arrest, severe allergic reactions (anaphylaxis), malignant hyperthermia, dangerous potassium elevation (hyperkalemia), and prolonged inability to breathe — require immediate emergency medical response.

• Children and hidden muscle disease: Succinylcholine has caused cardiac arrest and death in apparently healthy children who had undiagnosed muscular dystrophy. Use in children is restricted to true emergency airway situations.
• Malignant hyperthermia: In genetically susceptible individuals, succinylcholine can trigger a rapid, life-threatening rise in body temperature with severe muscle rigidity, fast heart rate, and organ failure. People with a known or suspected family history of this condition must not receive it.
• Hyperkalemia (high potassium): The drug can release large amounts of potassium into the blood, causing dangerous or fatal heart arrhythmias — especially in patients with burns, major trauma, nerve injuries, or certain chronic conditions.
• Medication errors: Accidental administration of succinylcholine to the wrong patient can cause paralysis, respiratory arrest, and death. Strict storage and labeling practices are essential.
• Anaphylaxis: Severe, life-threatening allergic reactions have been reported; cross-reactivity with other muscle relaxants is possible.
• Bradycardia: A dangerously slow heart rate can occur, especially in infants and children or after a second dose; pretreatment with atropine may be used to reduce this risk.
• Prolonged paralysis: Patients with low levels of the enzyme plasma cholinesterase (due to genetics, pregnancy, liver disease, or certain drugs) may experience much longer-than-expected muscle paralysis.
• Increased eye and intracranial pressure: Avoid use when a rise in eye pressure would be harmful (e.g., penetrating eye injury, narrow-angle glaucoma) unless benefits clearly outweigh the risks.

Several medications and substances can interact with succinylcholine, primarily by making its muscle-blocking effect stronger or longer-lasting.

• Drugs that enhance neuromuscular blockade: promazine, oxytocin, aprotinin, certain non-penicillin antibiotics, quinidine, beta-blockers, procainamide, lidocaine, trimethaphan, lithium carbonate, magnesium salts, quinine, chloroquine, metoclopramide, and terbutaline — all can intensify or prolong paralysis
• Volatile anesthetic gases (isoflurane, desflurane): increase the risk of malignant hyperthermia and enhance muscle blocking
• Drugs that reduce plasma cholinesterase activity — including oral contraceptives, glucocorticoids, and certain MAOIs — slow the breakdown of succinylcholine and can prolong paralysis
• Irreversible cholinesterase inhibitors — such as organophosphate insecticides, echothiophate, and some cancer drugs — can dramatically extend the drug's effects
• Other neuromuscular blocking agents: if used in the same procedure, effects may be additive or antagonistic — the care team must plan accordingly

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Do not use if you have a skeletal muscle myopathy (muscle disease) such as muscular dystrophy — this is a contraindication
• Do not use if you or a family member has a known or suspected genetic susceptibility to malignant hyperthermia
• Do not use in the acute period after major burns, multiple trauma, extensive nerve damage, or upper motor neuron injury — severe potassium spikes can be fatal
• Tell your care team about any previous allergic reaction to succinylcholine or any other neuromuscular blocking agent
• Tell the team if you have low plasma cholinesterase activity — due to genetics, liver disease, kidney disease, pregnancy, or certain medications — as paralysis may last much longer than normal
• Pregnancy: succinylcholine crosses the placenta; plasma cholinesterase is lower during pregnancy, which can prolong effects; the newborn may experience temporary breathing problems with high or repeated doses
• Children: use is restricted to emergency airway situations due to the risk of cardiac arrest from undiagnosed muscle disease
• Older adults: dose should be selected carefully given the greater likelihood of reduced organ function and other medical conditions
• Patients with fractures or muscle spasms: initial muscle twitching can worsen existing injuries — close monitoring is required
• Patients with elevated eye pressure conditions (e.g., narrow-angle glaucoma or a penetrating eye injury) should be assessed carefully before use

Too much succinylcholine can cause prolonged muscle paralysis well beyond what is needed for the procedure, which may show up as muscle weakness, reduced ability to breathe, very low breathing volume, or complete inability to breathe (apnea). The main treatment is maintaining an open airway and providing breathing support until the patient can breathe normally on their own again. With higher or prolonged doses, the type of muscle block can also shift in a way that makes it harder to reverse, requiring additional monitoring and management by the clinical team.

Succinylcholine stimulates nerve-muscle junction receptors to cause a brief burst of muscle activity (seen as twitching), then blocks further signals, producing complete muscle relaxation. It also stimulates nerve pathways that regulate heart rate and rhythm, which can cause bradycardia, tachycardia, or even cardiac arrest — effects made stronger by certain anesthetic gases. The drug raises pressure inside the eyes and can temporarily increase pressure inside the skull. It does not affect consciousness, the sense of pain, or mental awareness, and has no direct effect on the heart muscle itself, the uterus, or other smooth muscle.

After an intravenous dose, succinylcholine works within less than a minute and is cleared from the blood very rapidly — levels fall below detectable limits within about 2.5 minutes. The body breaks it down quickly using an enzyme in the blood called plasma cholinesterase (pseudocholinesterase), first into succinylmonocholine and then into succinic acid and choline. About 10% of the drug leaves the body unchanged through the urine. In children, the drug may need a relatively higher dose than expected based on body weight alone, due to differences in how the drug distributes through the body compared with adults.

Store in refrigerator 2°C to 8°C (36°F to 46°F).