A short-acting muscle relaxant for anaesthesia
Mivacurium
A short-acting muscle relaxant given by an anaesthetist, useful for shorter procedures.
What is Mivacurium?
Mivacurium is a muscle relaxant given only by an anaesthetist during a general anaesthetic. It temporarily paralyses the muscles, including the breathing muscles, so a breathing tube can be placed and the muscles stay still for surgery. You are always asleep first and a machine breathes for you throughout. It is short-acting, which suits shorter procedures, and it is broken down by the same blood enzyme as suxamethonium. People with a rare enzyme difference may stay relaxed for longer, which the anaesthetist manages by keeping you asleep and breathing on the machine until it passes.
Education and reference only. This is a plain-language guide to Mivacurium — 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
Mivacurium is a non-depolarising muscle relaxant used during general anaesthesia. It relaxes the muscles so the anaesthetist can place a breathing tube and keep the muscles still during surgery. Its main feature is that it is short-acting, which can be helpful for shorter operations. It is broken down by the same blood enzyme (pseudocholinesterase) that breaks down suxamethonium. It is given as an injection into a vein by an anaesthetist, only when you are asleep and your breathing is supported by a machine.
How it works
Mivacurium acts at the junction between nerves and muscles, blocking the signal that makes muscles contract so they relax. It is broken down by an enzyme in the blood called pseudocholinesterase — the same enzyme that clears suxamethonium — which is why it is short-acting. The block is checked with a nerve monitor and a machine breathes for you while the muscles are relaxed. Because it depends on this enzyme, its duration can be longer in people who have a low or different form of it.
Company & origin
Originated / developed by: Generic (long-established).
A short-acting muscle relaxant used in the UK by anaesthetists, broken down by the same blood enzyme as suxamethonium.
Practical use
How to take Mivacurium
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- This medicine is given only by an anaesthetist as an injection into a vein, never taken at home.
- You will always be fully asleep under general anaesthetic before it is given.
- A breathing tube is placed and a machine breathes for you while the muscles are relaxed.
- The anaesthetist monitors the block closely and supports you until it wears off.
- Tell your anaesthetist beforehand if you or relatives have ever stayed paralysed unusually long after an anaesthetic.
Weighing it up
Advantages & disadvantages of Mivacurium
Advantages
- Short-acting, which suits shorter operations and procedures.
- Its effect generally wears off without needing reversal in most people.
- A well-established option that anaesthetists know and use when a brief relaxant is helpful.
Disadvantages
- Can release histamine, sometimes causing flushing or a drop in blood pressure.
- Lasts much longer in people with a rare enzyme deficiency, the same one that affects suxamethonium.
- It must always be used with a breathing machine and close monitoring by an anaesthetist.
Practical use
Good to know
You are always fully asleep before mivacurium is given, and a machine breathes for you the whole time, so you are never aware of being paralysed. Its short action makes it convenient for shorter procedures. The key point to understand is that mivacurium is broken down by the same blood enzyme as suxamethonium, so people who have a rare inherited difference in that enzyme (pseudocholinesterase, or suxamethonium apnoea, deficiency) may stay relaxed for much longer than expected. If that happens, the team simply keeps you asleep and breathing on the machine until it wears off, and you would be advised to tell future anaesthetists. As with all these medicines, malignant hyperthermia and severe allergy are the key emergencies the team watches for.
Who should not take it / use with caution
- People known to have pseudocholinesterase (suxamethonium apnoea) deficiency are usually avoided or managed with great care.
- People who have had a severe allergic reaction to mivacurium or similar muscle relaxants should not be given it.
- Any decision is made by the anaesthetist after reviewing your health and previous anaesthetics.
Monitoring
- Continuous monitoring of breathing, oxygen, heart rate and blood pressure throughout.
- A nerve monitor is used to check the depth and recovery of muscle relaxation.
- The team watches for prolonged relaxation, flushing or any sign of a severe allergic reaction.
Side effects
- Flushing of the skin or a temporary drop in blood pressure from histamine release.
- Prolonged relaxation in people with the enzyme deficiency, managed by keeping you asleep on the machine.
- Rarely, a severe allergic reaction, which the team is trained to treat immediately.
Key interactions
- Its effect can be prolonged by medicines and conditions that lower the breakdown enzyme.
- Some antibiotics and other anaesthetic drugs can change how it works.
- The anaesthetist manages all interactions directly in the operating theatre.
Available as: Injection into a vein, given only by an anaesthetist in hospital.
Answers
Mivacurium: frequently asked questions
Will I be aware while my muscles are relaxed?
No. You are always fully asleep under general anaesthetic before mivacurium is given, and a machine breathes for you, so you are not aware of being paralysed.
Why is mivacurium used?
It is short-acting, which makes it convenient for shorter operations and procedures; in most people it wears off on its own.
Why might it last longer for some people?
It is broken down by the same blood enzyme as suxamethonium, so people with a rare inherited difference in that enzyme can stay relaxed much longer than expected.
What happens if it lasts too long?
The team simply keeps you safely asleep and breathing on the machine until it wears off, and you would be advised to tell future anaesthetists.
Why did my skin flush?
Mivacurium can release histamine, a natural body chemical, which may cause flushing or a drop in blood pressure; the anaesthetist watches for and manages this.
Authoritative sources
- BNF
- NICE CKS
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