Opioids are medicines taken to help reduce pain. They work on the central nervous system to slow down nerve signals between the brain and the body. This can reduce feelings of pain, but it can also produce adverse effects, ranging from constipation to dangerous slowing down of a person’s breathing.
Opioids can also increase the production of the hormone dopamine in the brain. Dopamine can produce feelings of pleasure and pain relief.
Opioid medicines are divided into two groups:
Commonly used opioid medicines contain active ingredients such as buprenorphine, codeine, fentanyl, hydromorphone, methadone, morphine, oxycodone, tapentadol and tramadol.
These medicines can be taken in many different ways, including as tablets or pills, injection or patches on the skin.
All opioids come in varying strengths. The measurement of strength is called ‘oral morphine equivalent daily dose’ (OMEDD). It’s useful to understand the total OMEDD being taken. A doctor or pharmacist can help calculate this.
Opioids may be recommended by a health professional for the treatment of acute pain and chronic pain caused by cancer. However, evidence shows these medicines are not very useful in helping to manage chronic non-cancer pain.
Find out more about pain in general
Find out more about chronic pain
Evidence suggests that harmful effects are more likely to happen to people who take opioids for 3 months or more, or who take higher doses of opioids. The harms from opioids can range from mild to severe and can end up causing death.
Some harms, such as constipation, nausea and drowsiness, tend to occur for a lot of the people who take opioids. Longer term use of opioids increases the risk of bone fractures (breaks), becoming dependent on the opioid and experiencing depression.
Opioids can actually cause more pain. This is called opioid-induced hyperalgesia, and it can occur with long-term use. It happens because taking opioids has made specific nerves and the brain more sensitive to pain.
People taking opioids also need to be careful about mixing them with other medicines that can make them feel sleepy or increase the effects of alcohol. It’s important to tell a doctor about all the medicines being taken.
Evidence shows that the longer someone takes an opioid, the less pain relief they have. This is because the brain gets used to that opioid dose. This effect is known as tolerance and can lead a person to take higher doses or more types of opioids in order to get the same pain relief.
Dependence is different from tolerance. When someone is dependent on their opioid medicine, they will experience withdrawal symptoms if the opioid dose is reduced or stopped. Dependence can occur within one month of starting to take an opioid.
For some people, the main reason they continue to take opioids long-term is to avoid withdrawal symptoms, although they may not realise this. They mistakenly think the opioid is working to reduce pain, when in fact it’s only reducing withdrawal symptoms, which can include pain.
Because opioids can help reduce acute pain and cancer pain, people with chronic non-cancer pain often expect opioids will also reduce or stop the pain they’re feeling. But unfortunately there is no such thing as a ‘pain killer’ and this is especially true for people experiencing chronic non-cancer pain. Opioids can improve pain and the ability to do day-to-day tasks. But this improvement is small and the harms of these medicines also need to be taken into account.
Medical experts recommend that people living with chronic non-cancer pain should first try to manage pain using combinations of treatments and medicines that include:
These treatments are recommended because they can be effective and safe, even more so when done at the same time.
Opioid pain medicines should only be recommended after someone has tried to get the most out of the above treatments but has not felt enough improvement. Even then, it may not be appropriate to take them.
If a person with chronic non-cancer pain and their doctor agree the potential benefits of an opioid outweigh the potential harms then one might be prescribed.
There are many reasons why an opioid is not likely to be recommended as part of management. One reason is when the risk of harm is increased, such as when a person already has a mental health condition such as anxiety, depression or post-traumatic stress disorder. Other reasons might include that a sedative (medicine that causes sleepiness) is already prescribed or there is a past or current substance use disorder involving alcohol and other drugs.
If a decision to prescribe an opioid for chronic non-cancer pain has been made, then the medicine should first be taken for a trial period. The aim of a trial is to better understand how the person responds to the opioid, as well as work out the lowest dose needed to improve pain and ability to do day-to-day tasks.
Benefits are weighed against the harms at the end of the trial to help decide whether to continue taking an opioid. If there is no meaningful improvement in symptoms, it is very unlikely that opioid treatment will be helpful. So stopping the opioid is recommended.
If benefits outweigh harms, there can be an agreement between the patient and doctor to continue the trial for another limited time. It’s important to continue regular reviews of harms and benefits.
The MedicineWise app is a useful tool for monitoring and recording all medicines a person is taking.
If the benefits outweigh the harms after a trial of taking an opioid, the trial can be continued for another period of time. But improvement in the short term does not predict success in the long-term.
In fact, many people with chronic non-cancer pain who take an opioid feel worse or find that the medicine doesn’t work as well the longer they take it. It happens for different reasons. These may include harms such as developing a dependence (physical, psychological or both), opioid-induced hyperalgesia, tolerance or withdrawal.
Another problem that can occur when continuing to take an opioid is positive reinforcement. This means the longer an opioid is taken, the more likely it is for a person to continue taking it, even when experiencing harms. This is commonly called an addiction or dependency, or opioid use disorder.
Opioid use disorder can lead to problems or distress such as:
If you think that you or someone you know has opioid use disorder, seek help as soon as possible. A doctor can help with an assessment and appropriate treatment.
Find a list of Australian alcohol and other drug support services in the Alcohol and Drug Foundation’s Help & Support directory or ring them on 1300 858584.
Opioids have limited value for people with chronic non-cancer pain because the benefits reduce over time, while their potential for harm increases. This is why any agreement to trial an opioid should also include a plan for lowering the dose or stopping the medicine completely. This is called tapering. Suddenly stopping opioids is not recommended because it can cause severe withdrawal symptoms.
Any decision on tapering should be made by the person living with chronic non-cancer pain and their doctor.
The benefits of tapering can include:
For help with making a decision about tapering, use this NPS MedicineWise resource: Lowering your opioid dose page 1.
Reducing or stopping an opioid is called tapering. It is a planned process that allows a person taking opioids to lower their dose or stop their opioid completely. It involves several aspects.4
For help with how to taper, use this NPS MedicineWise resource: Lowering your opioid dose page 2.
Withdrawal symptoms can occur because of physical or psychological dependence, which can take as little as one month to develop. So when a dose is lowered, a ‘withdrawal’ of an opioid can be experienced and the mind and body can respond negatively.
Tapering is when a decision is made together with a doctor to reduce the opioid dose with the aim of taking the lowest amount possible or stopping altogether. This is done slowly so that withdrawal symptoms aren’t experienced or at the very least, they’re minimised.
Withdrawal symptoms vary for each person. They are usually the opposite of what’s experienced when taking an opioid. For example, if opioids cause constipation, the withdrawal symptom will be diarrhoea.
Generally, symptoms may include: sweating, nausea, abdominal pain/cramping, diarrhoea, trouble sleeping, muscle aches, fast heartbeat, anxiety, runny nose and goose bumps.
Withdrawal symptoms as a result of tapering usually last for 4 to 10 days. While unpleasant, they are not dangerous and can be managed together with a doctor.
Withdrawal symptoms are best managed together with a doctor, who may prescribe medicines such as anti-emetics (eg metoclopramide) for nausea and vomiting. It’s important to have a responsible adult with the person experiencing withdrawal symptoms to check that medicines are taken correctly.
Unless advised otherwise by a doctor, there are also self-management strategies that may help with symptoms experienced by people withdrawing from opioids. General strategies may include:
Strategies and medicines for specific symptoms may include:
Taking too much of a medicine is called an overdose. With opioids, which slow down messages between the brain and body, this can cause symptoms such as slurred talking or dangerous slowing down of breathing to a point where it stops. In the worst case, opioid overdose can result in death.
Fortunately, opioid overdose can be reversed by cardiopulmonary resuscitation (CPR) and by giving a medicine called naloxone. Naloxone stops an opioid medicine from being able to work, which can reverse an overdose.
If you are concerned that you or someone you know may have taken too much of an opioid, immediately telephone your doctor or the Poisons Information Centre (13 11 26) for advice.
If urgent medical attention is needed call 000 or go to the Accident and Emergency Department at your nearest hospital.
For more information, see the Consumer Medicine Information (CMI) for the brand of medicine, available from the NPS MedicineWise Medicine Finder or from a pharmacist or doctor.
Useful support and resources for people taking opioids for chronic pain not caused by cancer:
Find out more about opioid medicines at healthdirect:
Last reviewed July 2021.