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The Risks of Opioid Therapy for Pain

Posted on April 8, 2021

The Risks of Opioid Therapy for Pain

Some examples of opioids include codeine, tramadol, morphine and fentanyl.

Opioids are prescribed for a number of complaints, including chronic back pain, cancer pain, and pain caused by serious injuries.

From 2017 to 2018, 5.6 million people in the UK received a prescription for opioid pain medicines of some form, which is 13% of the adult population. For context, 7.3 million people received a prescription for antidepressants, which represents 17% of the population. [1] This gives you an idea of how prevalent opioid medications are.

How do opioids reduce pain?

There are proteins called opioid receptors all over the body, including the spinal cord, brain and gut. What opioids do is attach to these receptors, preventing them from sending messages round the body. As the opioid receptors are responsible for transmitting pain signals, when they are blocked these signals do not get passed on. This prevents the body from feeling pain.

Opioids vs opiates: what’s the difference?

These two terms are often used interchangeably, but there is a difference. ‘Opioids’ is a broad term which refers to natural, synthetic and semisynthetic opioids such as the medications listed above. Opiates, on the other hand, refers specifically to natural opioids.

To give an example, heroin is both an opioid and an opiate, since it is a natural opioid. It is more commonly called an opiate, since this is the more specific term.

Fentanyl, by contrast, is a synthetic opioid and is therefore not an opiate. Opiates are specifically natural opioids. [2]

What you should know before you start opioid treatment for pain

Opioids offer effective pain relief, but carry several risks. Chief among these is the risk of dependence and addiction. Opioids are addictive, and should not be used for long periods unless absolutely necessary. This is the case even with small, therapeutic doses of opioids. Warnings have been added to most labels of opioid medicines in the UK for this reason. [3]

With this risk in mind, patients and their doctors need to agree on a strategy for ending treatment. There is a chance that patients will experience withdrawal symptoms after ending opioid treatment, especially if treatment has lasted for more than a month.

There is also a risk of unintentional overdose, which patients need to be aware of.

At the end of treatment, dosage should be tapered in order to minimise the risk of withdrawal symptoms. This tapering period can last for several weeks.

Hyperalgesia is also a risk. Hyperalgesia refers to increased sensitivity to pain that results from long-term opioid use.

We will go through all of these risks in more detail later in this page.

What are the risk factors for opioid treatment?

For some, it would not be a good idea to take opioids for pain relief. Opioids carry a risk of dependence, and this risk is higher for some people. Risk factors include your medical history, any mental health problems you may have had, your personal substance use history, and your family history.

Medical risk factors include sleep apnoea, fibromyalgia and obesity. If you suffer from any of these, your risk of experiencing adverse effects due to opioid medication will be higher.

Mental health problems, such as severe depression or anxiety, constitute a risk factor for opioid medication. Mental health problems and addiction have a high correlation, which means that if you suffer from mental health problems you are more likely to become dependent on opioids.

If you have had substance use problems of any kind, that also elevates the risk involved with opioid treatment. Even a heavy smoking habit could be a sign that opioid treatment might not be the best option for you. Similarly, if you have had treatment for a substance use disorder (SUD) in the past then opioid treatment might put you at risk of a relapse.

Finally, family history of substance use is a risk factor for opioid medication because it can make you more vulnerable to developing a SUD. Research has shown that genetics play a part in addiction. [4] So does learned behaviour, which means that if you have a parent who uses substance that also elevates your risk of developing a SUD. [5]

The role of the doctor in prescribing opioids for pain

Given the risks of taking opioids for pain relief, doctors have certain responsibilities when prescribing these medications. According to the Centers for Disease Control and Prevention (CDC), doctors should follow certain guidelines when suggesting opioids as a potential pain relief option. The CDC list 12 guidelines; we’ve condensed them a little bit and listed them below.

  • Avoid prescribing opioids for chronic pain, where possible. Opioids work best when used for short time periods only. Chronic conditions can last for months or years, which makes opioids a less effective and more risky option for these sorts of conditions. With chronic conditions, your doctor should explore other options with you, including non-pharmaceutical options and medications that are not opioids. (We will discuss alternatives to opioids later in this page)
  • For acute pain, prescribe the lowest possible dose, for the shortest time necessary. Acute pain normally only lasts for short time periods, and the amount of time you take opioid medication should reflect that. According to the CDC, you will rarely need to prescribe opioid medications for longer than seven days; three days is often enough
  • Decide on certain treatment goals with you, the patient. Pain relief medication is there to improve your quality of life, but it comes with certain risks. For this reason, a course of opioids is only really worth the risk if it leads to a significant reduction in pain. The CDC suggests that ‘a 30% improvement in pain and function is considered clinically meaningful.’ [6] Anything short of that, and your doctor should lower or taper the dosage. Alternatively, they should tell you to stop taking the opioids altogether. The key point is that opioids need to be having a marked positive effect, in line with your treatment goals, otherwise they simply are not worth the risk of addiction and dependence
  • Hold regular evaluations with the patient to check how opioid treatment is progressing. Due to the addictive nature of opioids, doctors need to carefully monitor their patients once they have started taking this medication. They should check up on patients within 1 to 4 weeks of beginning the course of opioids, and then every three months (or more frequently if possible) after that
  • Risk factors need to be monitored on an ongoing basis. If there is any risk of an overdose, for example when a patient is showing withdrawal symptoms and is tapering off opioids, then the doctor should consider prescribing naloxone. Naloxone is a medication which counteracts the effects of an opioid overdose
  • Doctors should consider urine drug testing when prescribing opioids for chronic pain. This is to monitor for other prescribed medications or non-prescribed drugs. Urine testing should happen before prescribing opioids, and on a regular basis when opioids have been prescribed for a chronic condition
  • Doctors should offer evidence-based treatment for patients with opioid use disorder. This could take the form of a behavioural therapy, such as cognitive behavioural therapy, combined with a pharmacological treatment such as buprenorphine or methadone

Types of opioid for pain

There are a variety of different opioids licensed for prescription as pain relief medication. What your doctor prescribes will vary depending on the severity of your pain and the circumstances of your case. It will also depend on your history with substances and whether you have had any mental health problems in the past.

The most common opioids prescribed for pain are:

  • Buprenorphine
  • Codeine
  • Diamorphine
  • Dihydrocodeine
  • Fentanyl
  • Morphine
  • Oxycodone
  • Tramadol

Other opioids that are sometimes prescribed for pain are:

The risks of opioid therapy for pain

The risks of opioid therapy for pain include dependence, withdrawal, hyperalgesia, overdose, and various side effects. In the following section we go through these risks one by one and discuss how to deal with them.


Becoming dependent on opioids is the single biggest risk associated with taking this medication. Opioids are highly addictive and taking them for any amount of time, especially if you have a history of substance use, puts you at risk of becoming dependent. So, if you do need to take opioid medication, what can you do to minimise the risk of dependence? And how can you tell if you are becoming dependent?

  • Signs of dependence. There are lots of signs you can look out for if you are worried you might be becoming dependent on opioids. Here are some examples:
    • Changes in mood. If you begin experiencing abrupt changes in mood, that might be caused by opioid dependence. If you notice that your mood changes coincide with the opioids wearing off, that should be another warning sign
    • Taking more than the prescribed dosage of opioids. You should never take more opioids than you have been prescribed: this is dangerous and can lead to an overdose. If you find yourself doing so, speak to your doctor immediately
    • Taking opioid medication when you do not have any pain. This is a definite sign that you need to speak to your doctor and cut down on your opioid medication.
    • Using someone’s else medication, purchasing more medication illegally, or otherwise finding a way to take more than the required dose of opioids. This is a serious red flag, and suggests that you need to stop taking opioids as soon as possible
  • A note on stopping opioid medication. We’ll discuss this in more depth later on, but it is worth mentioning here. If you are becoming dependent on opioids, do not stop immediately. Going ‘cold turkey’, as it is known, can be dangerous for your health. You will need to taper off or use a pharmacological treatment to ease you off opioids. Speak to your doctor as soon as possible to discuss doing so
  • Taking opioid medication without becoming dependent. Although opioids are very addictive, it is possible to take them without becoming dependent. You have to be strict with yourself, use them for a short time period, and watch out for signs of dependence. We discuss how to take opioids safely in more detail below

Withdrawal caused by opioid medication

If you do become dependent on opioid medication for pain relief, then stopping the course of opioids will lead to withdrawal. Withdrawal from opioid medication can be very unpleasant, leading to a range of withdrawal symptoms.

Examples of withdrawal symptoms that might be caused by cessation of opioid treatment include:

  • Body aches
  • Diarrhoea
  • Difficulty sleeping
  • Irritability and agitation
  • Nausea and vomiting
  • Shivers
  • Sweating
  • Widespread or increased pain [8]

If you experience some or all of these symptoms after the end of a course of opioids, you are likely going into withdrawal. You should speak to your doctor as soon as possible.

Side effects of opioid pain medication

Another downside of opioid pain medication is that it causes several side effects. The most common are:

  • Constipation
  • Dizziness
  • Dry mouth
  • Nausea
  • Pruritis
  • Sedation
  • Vomiting

According to the Faculty of Pain Medication, ‘between 50 and 80% of patients in clinical trials experience at least one side effect from opioid therapy.’ [9] Most of these side effects disappear after treatment has been ongoing for a few days, apart from constipation and itching, which persist throughout treatment.

Patients should be informed about side effects before they begin a course of opioids for pain relief. Most side effects can be managed with the help of prophylactic treatments such as anti-emetics, drinking lots of fluids and (if necessary) opioid antagonists. Opioid antagonists work reasonably well for managing constipation although there is less evidence to support their use as a laxative compared with regular laxatives and drinking lots of water.

Opioid-induced hyperalgesia

Hyperalgesia is a condition which can occur after long-term use of opioids. It refers to an elevated sensitivity to pain. In other words, someone with hyperalgesia will experience things as painful that a normal person would not.

Hyperalgesia often occurs alongside regular pain, caused by a disease or injury. It is also distinct from ‘breakthrough pain’ which happens when someone develops a tolerance to opioids.

Hyperalgesia can be ‘primary’ and ‘secondary’. Primary hyperalgesia refers to pain which is felt at the site of an injury, whereas secondary hyperalgesia refers to pain that is felt all over the body.

Hyperalgesia normally resolves itself with a gradual tapering off of opioids. Other treatment options include switching to a different class of opioids, or taking a NDMA antagonist. Your doctor will look at the specifics of your case before deciding which of these options to recommend.


If you take too much opioid medication, this can cause an overdose. Overdoses are very serious and can be life-threatening.

There are lots of signs to look out for if you worry that you or a loved one may have experienced an overdose. They include:

  • Blue/purple lips or fingernails
  • Confusion or hallucinations
  • Difficulty breathing or no breathing
  • Heavy or unusual snoring
  • Poor coordination or balance
  • Slurred speech
  • Unresponsive or unconscious
  • Very small pupils in the eyes

If you think someone may have overdosed on opioid medication, call the emergency services immediately.

Tips for taking opioid medication safely

Despite the risks that are involved with opioid medication, it is possible to take it safely. Here are our tips for making sure you stay healthy and avoid dependence when taking opioid medication:

  • Make sure you take exactly the dose recommended by your doctor – never take more than they suggest.
  • Do not mix opioid medications. If you feel like you need more pain relief, speak to your doctor and they may be able to increase your dosage.
  • If you have any of the risk factors associated with opioid medication, such as sleep apnoea, try to avoid opioid treatment. If you are pregnant, especially, opioid medication is not recommended as there is a risk that opioids cross the placenta and affect the unborn child.
  • Tell any healthcare providers about your opioid medication. Opioids can react unpredictably with different medication, so it is imperative that medical staff know what medication you are taking in the event of an emergency.
  • Report any side effects of your opioid medication to a doctor as soon as you can.
  • Always check to see if opioid medication is within the expiry date before taking it.

And, for the safety of others:

  • Keep opioid medication out of the sight and reach of children.
  • Never let others take opioid medication prescribed for you. Dosage and type of opioid medication vary from person to person – allowing someone else to take your opioid medication could put them at risk of an overdose.

How do I stop taking opioid medication?

If you are worried that you may be dependent on opioid medication or have simply come to the end of your course of opioids, you will need to stop taking opioids. This needs to be done carefully, in order to avoid withdrawal symptoms as much as possible.

The key to stopping opioid medication is to do so slowly, tapering the dosage. Consult with your doctor on the exact dosages to take each day. The tapering process can sometimes last weeks or months, depending on how high the original dosage was.

The US Centers for Disease Control and Prevention has three tips for tapering opioid medication doses. They are:

  • Go slow. If you have been taking opioids for more than a year, a tapering rate of 10% a month is reasonable.
  • Make sure to check with your doctor or healthcare provider to tell them about any symptoms you may be experiencing.
  • Tapering can be emotionally distressing. It may be worth getting therapy during this period if you feel you would benefit from it.

Alternatives to opioid therapy for pain

If you are worried about the dangers of opioid medication for pain, there are alternatives. They include:

  • Injections or implants. For localised pain, caused by muscle spasms or trapped nerves, sometimes an injection of anaesthetics or other medication can help. For chronic pain, spinal cord stimulation is another option. This means having an implant inserted into your spinal cord which sends electric pulses that block chronic pain in the back, legs and arms.
  • Therapies that do not involve drugs. There are a range of therapies which do not include taking any medication. One popular nondrug therapy is acupuncture, which can be very effective for localised pain. Other alternative therapies include massage, meditation and biofeedback. Interventional therapies can also be useful. These include nerve blocks, and surgical procedures to cut malfunctioning nerves. You would need to see a pain specialist if you are considering an intervention like this.
  • Combination therapy. You can combine opioids with other, non-opioid medication if you want to minimise your opioid intake. Consult with a doctor before taking any other medication so that they can advise you what medications are safe to combine with opioids.

Final thoughts

Despite their incredible pain relief qualities, opioids carry a serious risk of dependence, as well as other side effects. However, it is possible to take them relatively safely if you follow the advice of your doctor, and take them for as short a period as possible.

If you or a loved one are suffering from severe pain and are considering opioid therapy, we wish you all the best, and we hope you are now better placed to make an informed decision.


[1] Public Health England, ‘Prescribed Medicines Review: Summary’, Dec 2020.

[2] Centers for Disease Control and Prevention, Opioid Overdose, Commonly Used Terms.

[3] UK Government, Medicines and Healthcare products Regulatory Agency (MHRA), Drug Safety Update, ‘Opioids: risk of dependence and addiction’, 23 September 2020.

[4] National Institute of Drug Abuse, ‘Genetics and Epigenetics of Addiction Drug Facts’

[5] L Chassin et al., ‘A longitudinal study of children of alcoholics: predicting young adult substance use disorders, anxiety, and depression’, 1999.

[6] Centers for Disease Control and Prevention, ‘Assessing Benefits and Harms of Opioid Therapy’.

[7] NHS ‘Controlling your pain with opioids: Information for patients, relatives and carers’.

[8] UK Government, ‘Guidance: Opioid medicines and the risk of addiction’.

[9] Faculty of Pain Medication, ‘Opioids for long term pain’.

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