Different types of painkillers

Pain can be mild, moderate or severe. It can be treated using different strengths of painkiller, depending on your level of pain. Your doctors and nurses will assess your pain and prescribe the best painkillers to help control it.

  • Mild pain is often treated with non-opioid drugs, for example paracetamol and anti-inflammatory drugs (Brufen®, Neurofen®).
  • Moderate to severe pain is usually treated with painkillers called opioids. These include dihydrocodeine (DF118 Forte®, DHC Continus®), codeine phosphate, tramadol, morphine, fentanyl and oxycodone.

Sometimes opioids are used to treat mild pain.

Non-opioids can be used in combination with opioids. Other medicines, known as adjuvant drugs, may also be used to control pain. Examples are bisphosphonates and steroids.

Some painkillers give quick relief that lasts for a short time. These are called short-acting painkillers. Long-acting painkillers (also called slow-release painkillers) are slower to control the pain but are effective for a longer time.

Strong painkillers can cause side effects in some people. If you have any side effects, tell your doctor or nurse.

Types of painkiller

Pain is often described as being mild, moderate or severe. Different types of painkillers are effective for the different levels of pain. Once your doctors and nurses have assessed your pain they will prescribe the best painkillers to help control it.

  • Mild pain is often successfully treated with mild painkillers called non-opioids.
  • Moderate to severe pain is usually treated with painkillers called opioids. Sometimes opioids are used to treat mild pain.

There are other medicines (adjuvant drugs) that are often given with painkillers to help relieve pain. These include steroids and muscle relaxants.

At first, you usually take a short-acting painkiller. These provide quick pain relief that lasts for a short amount of time. The dose can easily be adjusted until your pain is well controlled.

When the doctor knows how much of the painkiller you need to control your pain, you will usually change to a long-acting drug. Long-acting painkillers are usually slower to control the pain, but are effective for a longer period of time. They are also called slow-release painkillers.

Non-opioid drugs for mild pain

Mild pain is often successfully treated with painkillers such as paracetamol and anti-inflammatory drugs.

Paracetamol can be used for most types of mild pain. You can buy it from a pharmacy or supermarket. It has few side effects, but it is very important not to take more than the recommended dose. Higher doses can damage the liver. Talk to your doctor or specialist nurse as soon as possible if you think you have taken more than the recommended dose of paracetamol. Paracetamol does not reduce inflammation.

Anti-inflammatory drugs such as ibuprofen help reduce inflammation and swelling. They are good for treating pain in the skin, muscle or bone. Ibuprofen has many different brand names, including Brufen® and Neurofen®. You can usually buy these from a pharmacy or supermarket. Other anti-inflammatory medicines need to be prescribed by a doctor.

Check with your doctor or nurse before taking these types of medicines. They do not always work for everyone and may not mix well with other medicines you’re taking.

Anti-inflammatory drugs can cause indigestion and may irritate the lining of the stomach, so it’s important to take them after a meal or snack. Your doctor may prescribe another medicine to help protect your stomach. If you’ve had problems with stomach ulcers before, your doctor may suggest you don’t take anti-inflammatory drugs at all. Or they may suggest you use an anti-inflammatory gel, which you can rub onto the skin.

When taking these drugs, always check the recommended dose on the packet and never take a higher dose.

Be aware that some other medicines or tablets that you can buy from a pharmacy or supermarket, such as cold and flu remedies, may also contain paracetamol or anti-inflammatory drugs. If you are taking painkillers, you should be careful which other medicines you take, so that you don’t take more than the recommended doses. If you are unsure, check with a pharmacist before buying any over-the-counter medicines.

Opioid drugs for mild to moderate pain

Mild to moderate pain is treated with opioid drugs, such as:

  • dihydrocodeine (DF118 Forte®, DHC Continus®)
  • codeine phosphate
  • tramadol.

These drugs are often combined with paracetamol in a single tablet. For example, codeine and paracetamol make the painkiller co-codamol.

Combination painkillers have brand names such as:

  • Tylex®
  • Remedeine®
  • Solpadol®
  • Kapake® 
  • Tramacet®. 

Most are only available with a prescription. There is a limit to the number of tablets you can take in one day. If your pain isn’t controlled, it is important to let your doctor know so that they can give you stronger painkillers.

Opioid drugs for moderate to severe pain

Moderate to severe pain is treated with strong opioids, such as:

  • morphine
  • fentanyl
  • oxycodone.

Morphine, fentanyl, oxycodone, buprenorphine and diamorphine are all commonly used. Tapentadol, hydromorphone, methadone and alfentanil are used less commonly. We have more information about these drugs below.

With this type of painkiller, it’s important for your doctor to find the most effective dose for you. Two people with the same type of cancer may need different doses of the same drug, even if they are at the same stage of their illness.

You will usually start by having a low dose. The doctors will increase it gradually to a dose that controls your pain. If your pain increases or decreases, the dose of your painkiller can be changed. It can take a few days to adjust to taking a strong opioid painkiller, or to taking a higher dose.

Strong painkillers have side effects (see below). If you have side effects, tell your doctor or nurse. A different type of strong painkiller may be better for you and not cause side effects.

Other drugs may be used together with strong painkillers. For example, paracetamol or ibuprofen are often also prescribed. If your doctor or specialist nurse suggests this, it is important to take these as well as your strong painkiller.


You can take morphine as:

  • short-acting tablets (Sevredol®)
  • short-acting syrups (Oramorph®)
  • a short-acting injection
  • suppositories, which are usually short-acting
  • long-acting granules to mix with water (MST Continus®)
  • long-acting tablets and capsules (Morphgesic® SR, MST Continus®, MXL®, Zomorph®).

To begin with, you usually take a short-acting type of morphine every 2 to 4 hours. Your doctor or specialist nurse will explain to you how often to take the drug. It’s usually taken as a tablet or a liquid. Liquid morphine has a bitter taste but mixing it with a fruit drink can help.

When the doctor knows how much morphine you need to control your pain, you will usually change to long-acting drugs. These release the morphine dose very slowly over a period of either 12 or 24 hours, depending on which type you are taking. You may still need to take short-acting morphine in between if you get breakthrough pain.

You may have morphine as an injection or as an infusion using a syringe driver. This is useful if you are feeling sick or vomiting. Occasionally, morphine suppositories are used.


You can have fentanyl in different ways.

Fentanyl patches

These look like waterproof plasters. You stick them onto your skin and the drug is slowly released through the skin. The patches are changed every three days and each new patch is put on a different area of skin.

When you first use the patch, it takes around 12 to 24 hours for the fentanyl to reach its level in the blood. During this time, you’ll usually need to take a short-acting opioid, such as morphine, to keep the pain under control.

You should place patches on parts of your body that are not hairy. Write the date on the patch so you remember when to change it. Patches can sometimes cause a slight skin rash. Try to stop the patch getting hot by protecting it from the sun, hot water, heat pads or hot water bottles. Let your doctor or specialist nurse know if you have a temperature, as it may affect how the medicine is absorbed through your skin.

Buccal, sublingual or nasal fentanyl

There are three types of buccal fentanyl:

  • a short-acting lozenge (Actiq®)
  • a tablet (Effentora®)
  • a dissolvable film (Breakyl®).

You put buccal medicines in your mouth between your cheek and gum. The drug is absorbed from here into the body. Buccal fentanyl works best for breakthrough pain.

Fentanyl can also be given as a sublingual tablet (Abstral®, Recivit®) that you put under the tongue. Or you can have it as a nasal spray (Instanyl®, Pecfent®).


You can take oxycodone by mouth as short-acting capsules or liquid (Lynlor®, Oxycodone®, OxyNorm®, Shortec®) every 4 to 6 hours. Or you can have long-acting tablets (Abtard®, Longtec®, OxyContin®, Reltebon®, Targinact®) every 12 hours.

Oxycodone can also be given by injection, or as an infusion using a syringe driver.

You may have oxycodone if you can’t have morphine or if it doesn’t work well for you.


This may be given as:

  • a skin patch (Hapoctasin®, Transtec®) that you change every three days
  • a skin patch (BuTrans®) that you change every seven days
  • a tablet (Gabup®, Prefibin®, Subutex®, Temgesic®, Tephine®) that you dissolve under the tongue every 6 to 8 hours.


You may have diamorphine if you can’t swallow and need to have painkillers by injection, or as an infusion using a syringe driver. Diamorphine is converted to morphine in the body.


Tapentadol (Palexia®) is available as:

  • short-acting tablets
  • short-acting syrup
  • long-acting tablets.


Hydromorphone is available as:

  • short-acting capsules (Palladone®)
  • long-acting capsules (Palladone® SR).


Methadone may be given as:

  • a tablet (Physeptone®)
  • a syrup
  • an injection (Physeptone®, Synastone®).

It’s usually only given under close supervision from a specialist palliative care doctor or pain doctor. Methadone may help reduce nerve pain.


Alfentanil (Rapifen®) is another strong painkiller that is only given by injection or as an infusion using a syringe driver. It is more likely to be used if someone’s kidneys are not working well.

Managing pain during advanced cancer

Oncologist Sarah Slater explains how painkillers help people with advanced cancer.

About our cancer information videos

Managing pain during advanced cancer

Oncologist Sarah Slater explains how painkillers help people with advanced cancer.

About our cancer information videos

Side effects of strong painkillers

As with most medicines, some people will get side effects. These won’t affect everyone taking strong painkillers. Some of the more common ones are listed below.


Most strong painkillers cause constipation.

If you’re taking strong painkillers, you should also take a laxative throughout your treatment. Some laxatives soften stools and make them easier to pass. Others stimulate the bowel to push the stools along more quickly. Taking a combination of these two types of laxative is often best for preventing constipation. It’s also important to eat a diet high in fibre and to drink plenty of fluids (at least two litres or three and a half pints a day).


You may feel sick when you first start taking opioid painkillers. You may need to take an anti-sickness (anti-emetic) drug for at least the first week of treatment.

If you have sickness that doesn’t stop after seven days, let your doctor know. You may need to change to another painkiller.


This usually decreases within a few days once you are used to the dose. If you start to get drowsy when you have been taking strong painkillers for a while, you should tell your doctor or specialist nurse. This can sometimes happen if you are having other treatments to shrink the cancer that may have helped to reduce your pain. You may need a lower dose of your painkiller or a different type of painkiller.

Alcohol may increase drowsiness so it’s better to avoid it or only drink small amounts. You can gradually increase how much you drink if drowsiness isn’t a problem.

Feeling tired

Strong painkillers can make you feel tired. You should not drive if you have recently started taking strong painkillers or if you have increased the dose. This is because they may make you drowsy and slow your reactions.

Dry mouth

Strong painkillers can make your mouth dry. Chewing gum or using products containing artificial saliva can help. Tell your doctor or nurse if you have a dry mouth.

Other effects

If the dose of a strong painkiller is too high, it can cause other symptoms. It could make you:

  • confused
  • forgetful
  • have vivid dreams and hallucinations (seeing things that are not real)
  • have low blood pressure
  • slow, deep breathing
  • dizzy or faint.

Let your doctor know straight away if you have any of these side effects.

Remember that although all strong painkillers cause similar side effects, some may suit you better than others. If your pain is not well controlled, or if side effects are a problem, tell your doctor or nurse. They may change your dose or give you another type of strong painkiller.