Painkillers

What are painkillers?

Painkillers are medicines that are used to treat pain. There are a large number of painkillers available and they all have various brands. They can be taken:

• By mouth as liquids, tablets, or capsules.

• By injection.

• Via the back passage (rectum) as suppositories.

Some painkillers are also available as creams, ointments, gels or patches.

Types of painkillers

Even though there are 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 naproxen. Aspirin is also an NSAID; however, it is mainly prescribed (in low doses) to help to keep the blood from clotting - for example, for people who have had a heart attack in the past.

• Paracetamol.

• Weak opioids and strong opioids (sometimes called opiates). Examples of weak opioids include codeine and dihydrocodeine. Although commonly described as 'weak opioids', they are extremely effective analgesics often used to treat severe pain; however, they can lead to significant addiction and adverse effects, so should not be underestimated. Examples of strong opioids include morphine, buprenorphine, oxycodone, pethidine and tramadol.

Different types of painkillers are sometimes combined together into one tablet - for example, paracetamol plus codeine (co-codamol).

In addition to the above, some antidepressants and antiepileptic medicines can be used to treat neuropathic pain. The rest of this leaflet does not discuss these types of medicines.

For more information on them see the separate leaflet called Neuropathic pain (Neuralgia).

There are also other alternative methods for pain relief such as, transcutaneous electrical nerve stimulation (TENS) machine.

See the separate leaflet called TENS machines.

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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. 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 the separate leaflet called Anti-inflammatory tablets (NSAIDs) for more details.

Paracetamol. No one really knows for sure exactly how paracetamol works. But it 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 inflammation.

Opioids work by binding to certain receptors (opioid receptors) in the central nervous system, the gut and other parts of the body. This leads to a decrease in the way pain is felt and responded to, and it increases tolerance to pain.

See the separate leaflet called Strong painkillers (Opioids) for more details.

Which painkiller is usually prescribed?

The type of painkiller a doctor will prescribe depends upon:

• The type of pain.

• Any other health problems.

• The severity of the pain.

• The possible side-effects of the medicines.

Painkillers such as paracetamol are normally advised or prescribed if the pain is mild or moderate and there is no inflammation.

NSAIDs are generally advised or prescribed for people who have pain along with inflammation - for example, if where there is pain in the joints (arthritis) or muscles (back pain). 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 advise a safer medicine (paracetamol) even though it may not work as well. NSAIDs can be used with heat and ice treatment in joint, muscle or ligament injuries.

See the separate leaflet called Ice and heat therapy for pain relief.

Weak opioids are usually prescribed for more severe pain, or if other painkillers have not worked.

Stronger opioids are normally used to treat severe pain - for example, cancer-related pain, pain after an operation, or after a serious injury.

Anti-inflammatory medicines used as a cream (topical painkillers) are mainly used to treat pain in the soft tissues and muscles.

See the separate leaflet called Topical anti-inflammatory painkillers for more details.

How should I take painkillers?

People who are in constant pain are often recommended to take painkillers regularly. For example, if paracetamol has been prescribed it will normally be taken four times a day, every day, until the pain is better. Otherwise, painkillers should only be taken when needed.

For some chronic pain conditions, such as fibromyalgia and chronic tension headache, regular painkillers are not recommended. This is because non-medication treatments can be more helpful for these conditions and painkillers may even make the condition worse.

In 2021, the National Institute for Health and Care Excellence (NICE) updated several of its guidances on painful conditions, including low back pain and sciatica. These highlight some of the risks of side effects of pain medications, including addiction with strong (opioid) painkillers.

This means that doctors will recommend taking painkillers for the shortest time possible, in the lowest dose that is effective. Any concerns should be discussed with a doctor or pharmacist.

NSAIDs such as ibuprofen or diclofenac should be taken with or after food. This is because they can irritate the lining of the stomach and sometimes cause bleeding in the stomach. In some circumstances another medication will be prescribed alongside the NSAID (a proton pump inhibitor or PPI) to protect the stomach from irritation.

What is the usual length of treatment?

Painkillers should be taken for the shortest period of time possible, in the lowest dose that controls the 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 may need to take painkillers on a long-term basis. Examples include people with osteoarthritis or chronic back pain.

Side-effects of painkillers

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. The information leaflet which comes with medication will have more details.

NSAIDs

Most people who take anti-inflammatories, at least in the short term, have no side-effects, or only minor ones. When taken appropriately, the benefits usually far outweigh 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 or kidney problems.

See the separate leaflet called Anti-inflammatory tablets (NSAIDs) for more details.

Paracetamol

This is a safe medicine and side-effects are very rare if the maximum recommended dose is not exceeded. However, paracetamol can be very dangerous if too much is taken (overdose). Overdoses of paracetamol can happen by mistake, but some people intentionally take an overdose. The main effect of an overdose of paracetamol is that it can damage the liver permanently and can cause death.

Opioids

The most common side-effects are:

• Feeling sick (nausea) and being sick (vomiting) - particularly at the start of treatment.

• Constipation.

• Dry mouth.

Opioids can also cause drowsiness and confusion. People often 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.

See the separate leaflet called Strong Painkillers (Opioids) for more details.

Some painkillers may interact with other medicines. This may cause reactions, or reduce the effectiveness of one or other of the treatments.

Can I buy painkillers?

Various painkillers can be bought, including paracetamol and some NSAIDs (eg, ibuprofen, aspirin and naproxen). Weaker opioids, such as codeine, are only available to buy in combination with paracetamol or ibuprofen. The dose of codeine in these combination tablets is lower than the doses that are available on prescription. It is only possible to buy a few days' supply of the weaker opioid combination tablets. If these are needed more than three days then this should be discussed with a doctor or pharmacist.

A prescription is needed for weaker opioids that are not in combination with paracetamol; most NSAIDs (for example, indometacin, or diclofenac), as well as stronger opioids (for example, morphine, diamorphine and tramadol) and opioid patches.

Who cannot take painkillers?

It is very rare for anyone not to be able to take some type of painkiller. The main reason why a painkiller might need to be avoided is following a serious side-effect or an allergic reaction to a particular type of painkiller in the past. Even if this has happened, a different type of painkiller will usually be available.

Aspirin cannot be taken by children under the age of 16 years, because there is a very small risk of the child developing a serious condition called Reye's syndrome.

Frequently asked questions

People frequently have questions about taking painkillers, particularly when buying them over the counter. Pharmacists are very well placed to answer most of these questions at the time but some common questions are answered below.

Can I take painkillers with antibiotics?

It is safe to take painkillers with antibiotics. It is often recommended, as simple painkillers such as paracetamol or ibuprofen can reduce fever as well as pain. Some antibiotics can cause side effects such as abdominal pain, vomiting and diarrhoea in which case NSAIDs should be avoided; paracetamol is a safer option.

Can I take painkillers with high blood pressure?

Blood pressure which is well controlled on medication does not cause a problem with painkillers. Uncontrolled blood pressure increases the risk of strokes and therefore medications such as NSAIDs might be advised against due to the risk of bleeding. However paracetamol is safe in this instance.

Can I take painkillers in pregnancy?

Paracetamol is safe throughout pregnancy. NSAIDs are not recommended in the first trimester (up to around 14 weeks of pregnancy) or the last trimester (from around 28 weeks of pregnancy). Codeine is also usually considered safe in pregnancy though the lowest possible dose is always advised and should be discussed with a doctor - the codeine does pass through to the baby in the womb. There is some evidence of babies being born with neural tube defects (a problem with the spine and the nerves coming from the spine) if codeine is used early in pregnancy and of some babies showing signs of opiate withdrawal if it is used late in pregnancy.

Which painkillers are safest for kidneys?

NSAIDs can cause damage to kidneys. This is most likely when taken for long periods of time and in older people, particularly those whose kidneys already have some damage. People who are known to have kidney disease would usually be advised to take paracetamol (and opiates if necessary). People on long term NSAIDs would normally be advised to have annual blood tests to check their kidney function.

What is a good painkiller for nerve pain?

Nerve pain does not often respond well to standard painkillers. This is why newer medications such as anti-epilepsy medication or anti-depressants may be used for this type of pain. These medications work particularly well for nerve pain.

How long do painkillers take to work?

Painkillers usually start working within a few minutes and then start wearing off again within a few hours. To avoid the pain coming and going, it is usually best to take painkillers regularly (for example, for an earache or toothache) as this works best at keeping pain at bay. This is not the recommendation for all long-term pain and can make some conditions, such as chronic daily headaches, worse rather than better.