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 most, but some people need to take them for a long time. You can buy some painkillers from pharmacies; this includes some NSAIDs, paracetamol, and some weak opioids (codeine or dihydrocodeine). If you buy painkillers that contain weak opioids and you need to take them for more than three days you must discuss this with your pharmacist or doctor.

What are painkillers?

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 by: mouth as liquids, tablets, or capsules, by injection, or via the rectum (back passage) - for example, suppositories. Some painkillers are also available as a creams or an ointment.

Even though there a large number of painkillers available, there are only three main types (each works in a different way). They are:

  • Non-steroidal anti-inflammatory drugs (NSAIDS). Examples of NSAIDs include; ibuprofen, diclofenac, and celecoxib. Aspirin is also an NSAID but nowadays it is mainly used (in low doses) to help to keep the blood from clotting.
  • Paracetamol.
  • Weak opioids and strong opioids (sometimes called opiates). Examples of weak opioids include: codeine, and dihydrocodeine. Examples of strong opioids include: diamorphine, morphine, oxycodone, and pethidine. Many people who need strong opioids are in hospital. Tramadol is also an opioid but fits somewhere in between a weak opioid and a strong opioid.

Different types of painkillers are sometimes combined together into one tablet - for example, paracetamol plus codeine (Co-codamol®), paracetamol plus dihydrocodeine (Paracodol®), aspirin plus codeine.

In addition to the above, some antidepressants and anti-epileptic medicines can be used to treat neuropathic pain. The rest of this leaflet does not discuss these types of medicines. For more information see separate leaflet called 'Neuropathic Pain'.

How do painkillers work?

NSAIDs work by inhibiting (blocking) the effect of enzymes (chemicals) 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 pain and inflammation. Not all NSAIDs are exactly the same, and some work in slightly different ways from others.

For more information see separate leaflet called 'Anti-inflammatory Painkillers'.

Paracetamol - no one really knows for sure exactly how paracetamol works. But it is also thought to work by blocking COX enzymes in the central nervous system (brain and spinal cord). Paracetamol is used to treat pain and to lower a high temperature. But it does not help with inflammation.

Opioids work by binding to certain receptors (opioid receptors) in the central nervous system (brain and spinal cord), the gut and other parts of the body. This leads to a decrease in the way you feel pain and your reaction to pain, and it increases your tolerance for pain.

Which painkiller is usually prescribed?

The type of painkiller your doctor will prescribe depends upon the type of pain you have, any other health problems you may have, how severe your pain is, and the possible side-effects of the medicines.

Paracetamol is normally prescribed if your pain is not too serious and you do not have inflammation.

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 the 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 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 on 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.

Topical painkillers (topical anti-inflammatory medicines) are mainly used to treat pain in the joints. For more information see separate leaflet called and 'Topical Anti-inflammatory Painkillers'.

How should I take painkillers?

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 be quite hard on the stomach and sometimes cause bleeding in the stomach.

What is the usual length of treatment?

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.

What are the possible side-effects?

It is not possible to list all the possible side-effects of each painkiller in this leaflet. However, as with all medicines, there are a number of side-effects that have been reported with each of the different painkillers. If you want more information specific to your painkiller then you should read the information leaflet that comes with the medicine.

Painkillers rarely cause serious side-effects:

  • NSAIDs - 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 problems. The leaflet dealing with anti-inflammatory painkillers gives more detailed information.

  • Paracetamol - is a 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. The leaflet dealing with paracetamol gives more information.

  • Opioids - the most common side-effects are nausea and vomiting (particularly at the start of treatment), constipation, and dry mouth. Opioids can also cause drowsiness and confusion. Some people can become tolerant to opioid painkillers (you need 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 doctor.

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.

Can I buy painkillers?

Yes - you can buy paracetamol, some NSAIDs (ibuprofen, diclofenac, and naproxen) and some weaker opioids. Weaker opioids, such as codeine, and dihydrocodeine, are only available to buy in combination with paracetamol or ibuprofen. It is only possible to buy a few days' supply of the weaker opioid combination tablets. If you need to take these for more that three days, then you will need to discuss this with your doctor or pharmacist.

You need a prescription for weaker opioids that are not in combination with paracetamol, most NSAIDs (for example, indometacin, or ketoprofen), as well as stronger opioids (for example, morphine, diamorphine, and buprenorphine).

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).

How to use the Yellow Card Scheme

If you think you have had a side-effect to one of your medicines, you can report this on the Yellow Card Scheme. You can do this online at the following web address:

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines may have caused. If you wish to report a side-effect, you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • Information about the person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.

Further help and information

The Pain Weblinks Page
Provides a comprehensive list of pain related support groups, and self-help advice.