International guidelines set out the types of painkillers that are most effective for different levels of pain. This is known as the analgesic ladder and recommends specific types of painkiller for mild pain, moderate pain and severe pain.

• Mild pain – Mild painkillers or anti-inflammatory drugs (eg paracetamol or ibuprofen)
• Moderate pain – Weak opioid painkillers (eg codeine)
• Severe pain – Strong opioid painkillers (eg morphine)

The idea behind the analgesic ladder is that if a person’s pain is not controlled by the painkillers on one level, their doctor should prescribe a drug from the next level, rather than try a different painkiller from the same group. For example, if you are taking a mild painkiller such as paracetamol, but you are still getting pain, or your pain gets worse, your doctor should prescribe a moderate painkiller. If the pain is still not controlled or if it increases, your doctor can prescribe painkillers used to treat severe pain.

If you have moderate or severe pain when you first see your doctor, you can start by taking painkillers from the second or third step of the ladder – you don’t have to start with painkillers from the mild group.

Often, painkillers from two different groups will be used at the same time, as they work in different ways. Other drugs that help to control pain, such as bisphosphonates and steroids can also be used alongside painkillers.

Painkillers such as paracetamol, aspirin and ibuprofen are often effective in controlling mild pain and can be bought from a pharmacist. Aspirin and ibuprofen can reduce inflammation as well as relieving pain, but they can cause indigestion and occasionally irritation of the stomach lining, which may make it bleed. To reduce the risk of stomach problems you should not take aspirin or ibuprofen on an empty stomach or with alcohol.

Always check the recommended dose on the packet and never take a higher dose than is recommended. Check with your doctor, nurse or pharmacist before taking them, in case they interact with other medicines you are taking or are not suitable for you. You can tell if any other medicines or tablets you buy from the pharmacy (eg cold cures) contain aspirin or ibuprofen by checking the ingredients on the packet. Check with the pharmacist if you are not sure.

Moderate pain is treated with low-dose opioid drugs, such as codeine phosphate, dihydrocodeine (DF118 Forte®, DHC Continus®), or tramodol. These are often combined with paracetamol in a single tablet, (eg co-codamol or co-dydramol). These combinations of painkillers have brand names such as Tylex®, Remedeine®, Solpadol®, and Kapake® and are only available on prescription from a doctor. There is a limit to the number of tablets that can be taken in one day because of the paracetamol content.

Side effects of moderate painkillers

All opioid painkillers cause constipation. Your doctor may prescribe a laxative for you to take with these drugs. This type of painkiller may also cause drowsiness, which may be increased by alcohol. Some drugs may make your mouth dry, which can be a nuisance.

Strong painkillers are known as opioid analgesics. Morphine and diamorphine are the most commonly used. Other strong painkillers are fentanyl, oxycodone, hydromorphone, buprenorphine, and methadone.

With this type of painkiller, it is important for your doctor to find the most effective dose for you. Two people with the same type of cancer, at the same stage of their illness, may need different doses of a drug. It is usual to start at a low dose and build up gradually to get the best pain relief. The dose can be changed and other painkillers can also be used, so that the pain is kept under control.

Side effects of strong painkillers

It can take a few days to adjust to taking strong painkillers. They may cause drowsiness. This usually passes within a few days once you are used to the dosage.

Strong painkillers affect people in different ways. It is fine to drink small amounts of alcohol while you are taking strong painkillers, but the combination may make you very drowsy.

Painkillers may also make you feel tired. You can talk to your GP about how this may affect you at home and at work. If you are planning to drive, or to work with machinery, you should check with your GP before taking strong painkillers. Don’t drive if you don’t feel fully alert or if your reactions are slowed.

All of the strong painkillers have similar side effects. The most common physical side effects are constipation and sickness, which can be relieved with other medicines. Constipation is so common that if you are taking strong painkillers you should also take a laxative throughout your treatment. Some laxatives soften stools and make them easier to pass, while others stimulate the bowel so that it pushes the stools along more quickly. A combination of these two types is often best at preventing constipation. Your doctor will be able to advise which are the best ones for you to take.

Some people feel sick when they first start taking strong painkillers, so they may need to take an anti-sickness drug (anti-emetic) for at least the first week of treatment. If you are starting strong painkillers, it is a good idea to discuss laxatives and anti-sickness drugs with your doctor.

These drugs can make your mouth dry and this can be a nuisance. This symptom can be relieved by drinking plenty of liquid. Chewing gum can also help. If the dose of strong painkillers is too high, they can cause slow, deep breathing and low blood pressure, which may make you feel dizzy or faint. Let your doctor know straight away if you have any of these effects.

Morphine is the most commonly used strong painkiller and can be taken in various ways:

• short-acting tablets (Sevredol®)
• long-acting tablets and capsules (Morphgesic® SR, MST Continus®, MXL®, Zomorph®)
• short-acting syrup (Oramorph®)
• granules to mix with water (MST Continus®)
• suppositories inserted into the back passage (morphine)
• injection into the muscle (Minijet® Morphine Sulphate)
• injection with an anti-sickness drug (Cyclimorph®).

A short-acting type of morphine is usually taken every four hours to begin with, so that the dose can be adjusted until the pain is well controlled. It can be taken as a tablet or a liquid. Liquid morphine has a bitter taste that can be improved by mixing it with a fruit drink. Once the right dose has been worked out for you, you will be able to take long-acting tablets or capsules. The morphine dose is released very slowly, over a period of either 12 or 24 hours, depending on which type you are taking. There is also a slow-release liquid, made by mixing granules in water and taken as a drink.

If you are not able to swallow or are being very sick, there are other options such as injections or suppositories. Morphine suppositories release a constant amount of morphine over a period of at least 24 hours.

Side effects

As well as the usual side effects of strong painkillers, morphine can give a sense of well-being (euphoria) which makes you feel detached from what is going on around you.

A few people find that the side effects of morphine are too uncomfortable for them. They may have ongoing drowsiness or sickness, which is not relieved by the usual medicines. Other strong painkillers – such as fentanyl, methadone, oxycodone or hydromorphone – may suit them better, although they can cause similar side effects in some people.

Diamorphine is available as tablets, or for injection into a vein, muscle, or under the skin. Diamorphine is the most commonly used drug for people who can’t swallow and who need to have their painkillers by injection.

A constant dose of diamorphine can be given continuously by using a small pump known as a syringe driver. A syringe containing diamorphine is put into the driver and attached via a tube to a fine needle placed under the skin (subcutaneously). In this way a small dose of the drug is released at a constant rate for as long as the person needs it. This method of giving drugs is known as continuous infusion and is very effective in keeping people free of pain.

Syringe drivers are battery powered and portable so you can be up and about as usual. They clip easily onto a belt, fit into a pocket or can be placed in a specially designed holster that fits under your arm

Other drugs may be added to the syringe to control symptoms such as feeling sick (nausea) or vomiting.

Less commonly, diamorphine may be given slowly through a needle into a vein (intravenously), or into the fluid around the spinal cord, which is known as intrathecal analgesia or an epidural.

Fentanyl

Fentanyl is a type of opioid painkiller. It can be given by injection, skin patch or as a lozenge.

The patches (Durogesic® or DTrans®) look like waterproof plasters. They are stuck to the skin, and the drug is released slowly through the skin. The patch needs to be changed every three days, and the new patch is put on a different area of skin. The patches can be convenient, as you don't need to remember to take tablets regularly.

Fentanyl is also available as injections (Rapifen®) or as a short-acting lozenge, (Actiq®). The injection or lozenge can be used when patches have just been started, as it takes around a day for fentanyl to reach its maximum level in the blood. The short-acting fentanyl can also be helpful if people need an extra dose to help with a painful procedure, such as having a dressing changed.

Side effects

The side effects are the same as for all strong painkillers; the patches may also cause a slight skin rash where they are applied. Fentanyl causes less constipation for some people than other types of opioid drugs.

Warmth can make the fentanyl absorb more quickly through the skin, so if you have a high temperature it is important to let your doctor or nurse know immediately. It is also important to avoid heating the skin patch, so care should be taken when bathing or showering.

Hydromorphone

Hydromorphone is available as short-acting (Palladone®) and long-acting capsules (Palladone® SR). The side effects are the same as for all strong painkillers.

Methadone

Methadone is available as short-acting tablets or syrup, or for injection into a muscle or under the skin.

Buprenorphine

Buprenorphine is available as:

• a patch (Transtec®) that is changed every three days
• a patch (BuTrans®) that is changed every seven days
• a lozenge (Temgesic®) that is dissolved under the tongue every 6–8 hours
• by injection.

Oxycodone

Oxycodone is given as short-acting capsules or liquid (OxyNorm®) or long-acting tablets (OxyContin®).