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Suxamethonium is a drug that is used when a person needs to have a breathing tube placed in the windpipe, usually when they are having an anaesthetic. The drug relaxes the muscles while the tube is being inserted and the effect usually wears off in a few minutes. However, in people with suxamethonium apnoea, the effect lasts much longer. They remain paralysed and unable to breathe on their own for much longer, perhaps hours (apnoea means inability to breathe).
Suxamethonium apnoea occurs when a person has a low level of the enzyme cholinesterase (also known as butyrylcholinesterase or pseudocholinesterase) in the bloodstream. Cholinesterase destroys suxamethonium, so people with low levels of cholinesterase cannot destroy the drug as quickly as other people, hence the drug effects last longer. The same thing can happen with a similar drug called mivacurium.
People with suxamethonium apnoea are generally born with a low level of cholinesterase, and the condition runs in families. Some illnesses, particularly liver disease, can also cause people to have a low level of cholinesterase. Such illnesses on their own do not usually lead to suxamethonium apnoea, but could make the problem worse in people who were born with a low level.
Last Review Date: July 1, 2018