How local anaesthetics work
Local anaesthetics stop the nerves in a part of your body sending signals to your brain.
You won't be able to feel any pain after having a local anaesthetic, although you may still feel some pressure or movement.
It normally only takes a few minutes to lose feeling in the area where a local anaesthetic is given.
Full sensation should return when the medication has worn off a few hours later.
How local anaesthetics are used
Local anaesthetics are usually given by dentists, surgeons, anaesthetists, GPs and other doctors.
Some medications containing mild local anaesthetic are also available on prescription or over the counter from pharmacies.
Depending on what they're being used for, local anaesthetics can be given as injections, creams, gels, sprays or ointments.
Some of the main uses of local anaesthetics are outlined on this page.
Preventing pain during and after surgery
A local anaesthetic, usually given by injection, may be used along with a sedative medication to keep you relaxed while an operation or procedure is carried out.
Local anaesthetics are mainly used for relatively minor procedures, such as:
- a filling or wisdom tooth removal
- a minor skin operation, such as the removal of moles, warts and verrucas
- some types of eye surgery, such as cataract removal
- a biopsy (where a sample of tissue is removed for closer examination under a microscope)
A local anaesthetic may occasionally be used for more major surgery when it's important for you to be awake, such as during certain types of brain surgery, or to prevent pain after a major operation that's been carried out under a general anaesthetic.
Epidural and spinal anaesthetics
An epidural anaesthetic, often referred to as an epidural, is where a local anaesthetic is continually injected through a tube into an area of the lower back called the epidural space.
A spinal anaesthetic is a single injection into a similar space in the back.
Both types of anaesthetic can be used to numb large areas of the body by stopping pain signals travelling along the nerves in the spine.
They're often used during childbirth to ease the pain of labour or if a caesarean section is needed.
They can also be used to reduce the amount of general anaesthesia needed during some operations and can provide pain relief afterwards.
In some types of surgery, such as knee and hip replacements, they can be used in place of a general anaesthetic.
Peripheral nerve blocks
A nerve block is an injection of a local anaesthetic to numb the nerves supplying a particular part of the body, such as the hand, arm or leg.
It may be used so an operation can be carried out without needing a general anaesthetic, or to prevent pain afterwards.
An ultrasound scan is often used to pinpoint the correct nerve.
The injection shouldn't be painful and usually takes about 30 minutes to become fully effective.
When peripheral nerve blocks and epidural or spinal anaesthetics are used in place of general anaesthetics, they're often combined with sedation to make you feel drowsy and more relaxed.
Risks and side effects
Local anaesthetics are generally very safe and serious problems are rare.
You may have:
- some discomfort when the injection is given
- a tingling sensation as the medication wears off
- possibly some minor bruising, bleeding or soreness where the injection was given
You shouldn't experience any significant side effects.
You should move carefully until the anaesthetic has worn off as you may not notice if you injure yourself.
Some people experience temporary side effects from a local anaesthetic, such as:
- blurred vision
- twitching muscles
- continuing numbness, weakness or pins and needles
These problems will usually pass, but you should tell the healthcare professional in charge of your care if you experience any.
In very rare cases, you could have an allergic reaction to the local anaesthetic or develop serious problems, such as fits (seizures) or a cardiac arrest (when the heart stops pumping blood around the body).