Painkillers - Opioids

Strong opioids are medicines used to treat severe or long-term (chronic) pain. Although there are many types of strong opioids, morphine is the most commonly used strong opioid and usually the first one your doctor will prescribe. The most common side-effects are constipation, feeling sick (nausea), and tiredness. It is unusual for people who take a strong opioid to treat pain to become addicted to strong opioids.

What are strong painkillers (opioids)?

Opioids (sometimes called opiates) are medicines used to treat pain. There are many different types of painkillers that are suitable for different types of pain. Most doctors will start off prescribing a weak painkiller such as paracetamol or ibuprofen. If these do not work, depending on the type of pain you have, your doctor may prescribe an opioid.

Opioids are usually divided up into two groups:

  • Weak opioids - these include, codeine, dihydrocodeine, and tramadol.
  • Strong opioids - these include buprenorphine, methadone, diamorphine, fentanyl, hydromorphone, morphine, oxycodone, and pethidine.

Strong opioids are usually prescribed for more severe types of pain - for example, if you have had an operation or have been injured in a car accident. They may also be considered for people who have long-term (chronic) pain, when other painkillers have not worked.

Strong opioids can be taken as: liquids by mouth, quick-acting tablets and capsules, slow-release tablets and capsules, or sachets. They are also available as tablets that are held in the mouth - next to the gum (buccal tablets), patches for the skin, or injections. They all come in various different brand names, and not all brands are the same. Once you have started taking one brand you should stick to the same one, unless your doctor has told you to switch to another.

Although there are quite a few strong opioids, the most commonly prescribed one is morphine. If your doctor thinks that a strong opioid would help your type of pain then morphine is usually the first strong opioid to be prescribed. If this does not work, your doctor may consider switching you to a different one.

How do strong opioids work?

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.

How do I take strong opioids?

To start off with, you will usually be given a quick-acting strong opioid (morphine tablets or liquid) as well as a slow-release morphine tablet or capsule. The slow-release preparation is usually taken once or twice a day, depending on which brand you have been given. Slow-release preparations give a steady level of medicine in the body throughout the day. However, sometimes you can experience pain before you have your next dose of slow-release morphine; this is called 'breakthrough' pain. Quick-acting morphine is used to ease breakthrough pain. It can be taken every four hours, when you need to.

Your doctor will start you off on a low dose of slow-release morphine and increase this over a number of weeks until your symptoms have eased. It is a good idea to write down how much quick-acting morphine you are using each day, as your doctor can then use this information to increase the dose of your slow-release morphine in order to keep you pain-free.

If your doctor has prescribed a fentanyl patch for your skin, this should be applied to a dry non-hairy area of the skin and changed once every three days.

What are the possible side-effects?

As with all medicines, opioids have a number of possible side-effects. The most common side-effects are constipation, feeling sick (nausea) and drowsiness or feeling tired.

  • Constipation - when you start treatment with a strong opioid, your doctor will usually also prescribe a laxative. Laxatives help to ease and prevent constipation by softening the poo (stools), making it easier to pass, or they stimulate your bowel to push the stools along more quickly.
  • Nausea - feeling sick is a common side-effect when you first start taking a strong opioid. This usually passes after a week or so, once your body gets used to this medicine. Your doctor will usually prescribe an anti-sickness medicine (an anti-emetic) when you first start treatment. Tell your doctor if sickness lasts for more than a week. Changing to a different strong opioid may help.
  • Drowsiness and tiredness - again, this usually passes once your body gets used to this medicine. Drinking alcohol as well as taking a strong opioid may increase drowsiness, especially at the start of treatment or when the dose is being increased. It is better to avoid alcohol if you are taking a strong opioid, or to drink less alcohol than usual.

A dry mouth can also be a problem. Some people find drinking plenty of liquids or chewing gum may help with this.

If the dose is too high, these medicines can make you can feel very drowsy, and confused, as well as feeling dizzy or fainting (signs of low blood pressure). They can sometimes make you see things that are not there (called hallucinations), or you might have deep slow breathing. It is important to tell your doctor right away if you think you have any of these side-effects. The dose of your strong opioid may need to be decreased. If you have been prescribed a fentanyl patch and you get any breathing problems, marked drowsiness and confusion, dizziness, or slurred speech, remove the patch from the skin right away and speak to your doctor.

The above is not a comprehensive list - just the main possible side effects to look out for. For a full list of possible side-effects, see the leaflet that comes with your medicine.

What is the usual length of treatment?

Strong opioids may be taken for as long as they are helping to ease your pain. Some people take these medicines for many years.

Can I become addicted to strong opioids?

It is unusual for people who take opioids for pain to become addicted to strong opioids. However, you may find that if you have been taking strong opioids for a long time, they do not work as well as they did in the beginning. You may may need a higher dose to treat your pain. This is called tolerance.

Stopping opioids

Do not suddenly stop taking strong opioids. This is because you may get side-effects called 'withdrawal effects' if you stop them suddenly. Examples of withdrawal effects are: tiredness, sweating, a runny nose, stomach cramps, diarrhoea, and aching muscles. If you want to stop taking these medicines, you should discuss this with your doctor and bring the dose down slowly. Many people find that after a few months they can reduce their dose without their pain increasing. Your doctor will advise you.

Can I drive if I am taking a strong opioid?

It is not against the law to drive when you are taking strong opioids. However, you should not drive if are drowsy or confused. You are more likely to feel drowsy at the start of treatment and when you have a dose increase. It is your responsibility to judge whether you are fit to drive.

Can I buy strong opioids?

No, you cannot buy strong opioids. These medicines are only available on prescription, from a pharmacy. These medicines are also referred to as 'controlled drugs'. This means that they have to be stored in a special cupboard in the pharmacy and that doctors have to write these prescriptions in a certain way.

Travelling abroad

If you need to travel abroad with a strong opioid, you will need to check first with the embassy or high commission (of the country you are visiting) to see if they will allow you to take these medicines with you. If these medicines are allowed, you will then need a letter from your doctor which states your name, address, date of birth, the dates of travel in and out of the country and the country you're visiting. This letter will also need to list the medicines you're taking, the doses and the total amounts you're taking with you.

For people who are travelling for more than three months, a licence from the Home Office is required. Your doctor needs to fill in this form and send it to the Home office. To get a licence you can:

  • Contact the Home Office Drugs Licensing and Compliance Unit by telephoning 020 7035 6330.
  • Use this website to download a form:

Note: it can take up to two weeks for this form to be processed by the Home Office. It is best to allow plenty of time to apply for this licence.

Who cannot take strong opioids

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.

Other considerations

There are a number of other considerations for strong opioids:

  • Storage - if possible, they should always be stored in a locked cupboard and out of the reach of children.
  • After treatment stops - always return strong opioids to your pharmacy so they can be destroyed safely.

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.