Also called suxamethonium
Succinylcholine
A fast, short-acting muscle relaxant used during anaesthesia to paralyse muscles for placing a breathing tube.
What is Succinylcholine?
Succinylcholine, also called suxamethonium, is a very fast, short-acting muscle relaxant used during anaesthesia to paralyse the muscles so a breathing tube can be placed quickly. It is given only by anaesthetists who can control the airway and breathing. Its most serious risks are a dangerous rise in blood potassium (especially in people with burns, major injury or long-standing paralysis), triggering a rare life-threatening reaction called malignant hyperthermia, and unusually long-lasting paralysis in people with a low or abnormal cholinesterase enzyme. It is given as an injection in a controlled setting only.
Education and reference only. This is a plain-language guide to Succinylcholine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Succinylcholine, also known as suxamethonium, is a muscle relaxant used during general anaesthesia. Its job is to relax and briefly paralyse the muscles, including those around the airway, so an anaesthetist can quickly and safely place a breathing tube. It works very fast and wears off very quickly, which is why it is valued when speed matters. It is given as an injection and is used only by anaesthetists and emergency specialists who can take over breathing for the patient, because it stops the muscles, including the breathing muscles, from working temporarily.
How it works
Muscles move when a chemical messenger called acetylcholine signals them to contract. Succinylcholine works at the junction between nerves and muscles, where it first causes a brief twitching and then blocks further signalling, so the muscles relax and become temporarily paralysed. This lets the anaesthetist place a breathing tube smoothly. It is broken down very quickly by an enzyme in the blood called cholinesterase, which is why its effect is so short-lived in most people. In those who have low or abnormal levels of this enzyme, it is broken down slowly and the paralysis can last much longer than expected.
Company & origin
Originated / developed by: Generic (long-established).
A fast, short-acting muscle relaxant used in the UK during anaesthesia to paralyse the muscles for placing a breathing tube, given only by anaesthetists.
Practical use
How to take Succinylcholine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as an injection by an anaesthetist or emergency specialist, only where breathing can be fully supported.
- Tell your anaesthetist if you or any blood relatives have had a bad reaction to an anaesthetic, such as a very high temperature or prolonged paralysis.
- Mention any history of burns, major injury, long-standing paralysis or muscle disease, as these affect whether it is safe.
- Expect possible muscle aches in the day or two afterwards, which usually settle on their own.
- This is a hospital-only medicine; you will not take it yourself at home.
Weighing it up
Advantages & disadvantages of Succinylcholine
Advantages
- Works extremely quickly to relax the muscles, which is valuable when a breathing tube must be placed fast.
- Wears off very quickly in most people, so its effect is short-lived.
- A long-established medicine that anaesthetists know well.
Disadvantages
- Can cause a dangerous rise in blood potassium, especially after burns, major injury or paralysis.
- Can trigger malignant hyperthermia, a rare but life-threatening reaction, in susceptible people.
- Can cause unusually long-lasting paralysis in people with low or abnormal cholinesterase enzyme.
Practical use
Good to know
The most important things to understand about succinylcholine are its serious safety risks, which is why it is an anaesthetist-only medicine used with full control of the airway and breathing. First, it can cause a dangerous rise in blood potassium, which is especially risky in people with burns, major trauma, crush injuries or long-standing paralysis, and can lead to dangerous heart rhythms. Second, in susceptible people it can trigger malignant hyperthermia, a rare but life-threatening reaction with a sudden high temperature and muscle rigidity that needs immediate treatment. Third, people with low or abnormal cholinesterase enzyme break it down slowly, so the paralysis lasts far longer than usual and breathing must be supported until it wears off. It commonly causes muscle aches afterwards. Because it stops the breathing muscles, it is never used outside a setting where breathing can be fully supported.
Who should not take it / use with caution
- People who, or whose relatives, have had malignant hyperthermia or a known reaction to it must not be given it.
- People with known low or abnormal cholinesterase enzyme, in whom paralysis lasts dangerously long.
- People at high risk of dangerous potassium rises, such as those with major burns, crush injuries, or long-standing paralysis or muscle disease.
- People who have had a serious allergic reaction to succinylcholine.
Monitoring
- Continuous monitoring of breathing, oxygen, heart rhythm and blood pressure during anaesthesia.
- Watching for signs of a high temperature or muscle rigidity that could mean malignant hyperthermia.
- Making sure breathing is fully supported until the paralysis has worn off.
Side effects
- Muscle aches and stiffness in the day or two after surgery.
- A rise in blood potassium, which can be dangerous in certain people.
- Slow heart rate, especially with repeated doses, which the anaesthetist watches for.
- Rarely but seriously, malignant hyperthermia or a severe allergic reaction, treated as emergencies.
Key interactions
- Certain other anaesthetic gases can add to the risk of malignant hyperthermia in susceptible people.
- Some antibiotics and heart medicines can change its effect, so the anaesthetist takes the full medicine list into account.
- Medicines or conditions that affect the cholinesterase enzyme can make its effect last longer.
Available as: A solution for injection given during anaesthesia.
Answers
Succinylcholine: frequently asked questions
What is succinylcholine used for?
It is a fast, short-acting muscle relaxant used during anaesthesia to paralyse the muscles so an anaesthetist can quickly place a breathing tube.
Why is it only given by anaesthetists?
It paralyses the breathing muscles too, so it is only used where someone can fully take over and support breathing, such as during anaesthesia.
What is the danger with potassium?
It can cause a dangerous rise in blood potassium, which is especially risky in people with burns, major injury or long-standing paralysis and can disturb the heart rhythm.
Why might the paralysis last too long in some people?
It is broken down by an enzyme called cholinesterase; people with low or abnormal levels break it down slowly, so the paralysis lasts much longer and breathing must be supported.
Why do my muscles ache afterwards?
Muscle aches in the day or two after surgery are a common effect of succinylcholine and usually settle on their own.
The wider class
About Fast-acting muscle relaxant (for anaesthesia)
Succinylcholine belongs to the fast-acting muscle relaxant (for anaesthesia) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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