There are three main types of painkiller
: non-steroidal anti-inflammatory drugs (NSAIDS), paracetamol and opioids.
Each works in a different way. Most people only need to take painkillers
for a few days or weeks at the most, but some people need to take them for
a somewhat longer duration. You can buy some painkillers from pharmacies ;
this includes some NSAIDs, paracetamol, and some weak opioids (codeine or
dihydrocodeine). Painkillers are medicines that are used to treat pain.
There are a large number of painkillers available and they all come in
various different brand names. They can be taken : orally as liquids,
tablets, or capsules; by injection (intramuscular); via the back passage
(rectum) as suppositories; and, some painkillers are also available as a
creams or ointments for easy, local application.
Even though there a large number of painkillers available, there are only
three main types (each works in a different way). They are :
1. Non-steroidal anti-inflammatory drugs (NSAIDS), e.g., ibuprofen,
diclofenac and naproxen etc. Aspirin is also an NSAID. However, it is also
prescribed (in low doses) to help to keep the blood from clotting.
3. Weak & strong opioids and strong opioids (sometimes called opiates),
e.g., codeine and dihydrocodeine. Examples of strong opioids include
morphine, oxycodone, pethidine & tramadol.
Different types of painkillers are
sometimes combined together into one tablet - for example, paracetamol
plus codeine (co-codamol), or, fairly commonly, paracetamol and ibuprofen.
In addition to the above, some antidepressants and anti-epileptic
medicines can be used to treat neuropathic pain.
How do painkillers work ?
NSAIDs work by blocking (inhibiting) the effect of chemicals (enzymes)
called cyclo-oxygenase (COX) enzymes. COX enzymes help to make other
chemicals called prostaglandins. Some prostaglandins are involved in the
production of pain and inflammation at sites of injury or damage. A
reduction in prostaglandin production reduces both pain and inflammation.
Not all NSAIDs are exactly the same, and some work in slightly different
ways from others. See separate leaflet called Anti-inflammatory
Painkillers for more details.
Paracetamol - is also thought to work by blocking COX enzymes in the
brain and spinal cord (central nervous system). Paracetamol is used to
treat pain and to lower a high temperature. However, it does not help with
Opioids work by binding to certain receptors (opioid receptors) in your
central nervous system, your gut and other parts of your body. This leads
to a decrease in the way you feel pain and your reaction to pain, and it
increases your tolerance for pain.
NSAIDs are generally prescribed for people who have pain and inflammation
- for example, if you have pain in your joints (arthritis) or muscles
(back pain). This is because there is likely to be some inflammation
present and NSAIDs work well to treat pain as well as inflammation. NSAIDs
have a number of possible side-effects and they are not suitable for
everyone. For example, they are not suitable for people who have or have
had stomach ulcers. In this case a doctor may prescribe a safer medicine (paracetamol)
even though it may not work as well. Weak opioids are usually prescribed
for more severe pain, or if you have tried paracetamol and/or ibuprofen
and they have not worked. Stronger opioids are normally used to treat
severe pain - for example, cancer-related pain, pain after an operation,
or if you have had a serious injury. Anti-inflammatory medicines used as a
cream (topical painkillers) are mainly used to treat pain in your soft
tissues and muscles.
People who are in pain all the time are usually recommended to take
painkillers regularly. For example, if you have been prescribed
paracetamol you will normally take it four times a day, every day until
the pain is better. Otherwise, you only need to take painkillers when you
need them. If you are taking an NSAID such as ibuprofen or diclofenac, you
will need to take this with or after food. This is because they can
irritate the lining of your stomach and sometimes cause bleeding in your
stomach. Like all medicines, painkillers should be taken for the shortest
period of time possible, in the lowest dose that controls your pain. This
is to help avoid any side-effects. Most people only need to take
painkillers for a few days (for example, for toothache) or weeks (having
pulled a muscle). However, some people have painful conditions and need to
take painkillers on a long-term basis. Examples include people with
rheumatoid arthritis, osteoarthritis, or chronic back pain.
Most people who take anti-inflammatories have no side-effects, or only
minor ones. When taken appropriately, the benefit usually far outweighs
the potential harms. In particular, many people take a short course of an
anti-inflammatory for all sorts of painful conditions. However,
side-effects, and sometimes very serious possible adverse effects, can
occur. These include bleeding into the stomach and gut, and cardiovascular
Paracetamol : is a relatively safe medicine and side-effects are rare if
you do not take more than the maximum recommended dose. However,
paracetamol can be very dangerous if you take too much (overdose).
Overdoses of paracetamol can happen by mistake, but some people
intentionally take an overdose. The main problem with taking an overdose
of paracetamol is that it can damage your liver permanently and you can
die from this.
Opioids : nausea, vomiting, particularly at the start of treatment.
Constipation. Dry mouth. Can also cause drowsiness and confusion. Some
people can become tolerant to opioid painkillers (needing to take more to
get the same effect) and then depend upon them. This includes opioids that
can be bought in pharmacies. If you think you are depending on opioids and
need to take higher and higher doses, discuss this with your pharmacist or
Some painkillers may interact with other medicines that you might take.
This may cause reactions, or reduce the effectiveness of one or other of
the treatments. So, when you are prescribed a painkiller, you should tell
a doctor if you take other medicines.
Who cannot take painkillers ?
It is very rare for anyone not to be
able to take some type of painkiller. The main reason why you may not be
able to take a painkiller is if you have had a serious side-effect or an
allergic reaction to a particular type of painkiller in the past. Even if
this happens, your doctor will usually be able to choose a different type
of painkiller, which you will be able to take. Aspirin cannot be taken by
children under the age of 16 years, because there is a risk of the child
developing Reye's syndrome (very rare).