What is Opioid Induced Hyperalgesia?

Opioids are a class of drugs commonly used to treat moderate to severe pain. They can be used over prolonged periods to relieve chronic pain. Opioid induced hyperalgesia is a clinical picture which involves increasing pain in patients who are receiving increasing doses of opioids. Opioids are substances such as opium, morphine, heroin, codeine and methadone.


Opioid induced hyperalgesia (increased sensitivity to pain) occurs in many different patients, depending on the dose given and the pattern of administration. Most work has reported opioid induced hyperalgesia if you are receiving continuing treatment with opioids or stop taking opioids.

Risk Factors

  • If you are taking high doses of opioids, you may be more likely to experience increasing pain and sensitivity.
  • If you have medical conditions such as kidney failure or liver failure, the effects of opioid medications may be affected. Opioid drugs are broken down by the liver and excreted by the kidney. One of the after products of morphine is much more potent than morphine itself. It is undecided whether a build up of this after product is linked to being more sensitive to pain.
  • When you are on opioids and suddenly stop taking the medication, evidence has shown that hyperalgesia has been one of the many symptoms associated with stopping opioid medications.


Doctors may consider this condition in patients who have a history of;

  • increasing sensitivity to pain,
  • pain that worsens despite high doses of opioids and
  • pain that becomes more wide-spread around the body.

Clinical Examination

When the doctor is examining you, some of the following signs may be found. On examination, you may complain of pain from non-painful stimuli, such as soft touching of the skin with cotton wool.
There may be increased activity in your nervous system. These signs include;

  • myoclonus (uncontrollable twitching and jerking of muscles or muscle groups),
  • seizures (due to abnormal electrical activity in the brain causing things such as abnormal movements, spasms, or changes in behaviour).


Research has shown that opioid induced hyperalgesia is a significant consequence of taking opioid medications. If you are taking such medications and are experiencing increasing pain, the use of alternative pain killers and stopping opioids may need to be considered.
In most cases, the first step is to look at reducing or discontinuing the current opioid.
Alternatively, the doctor can look at changing your opioid to one with less risk of toxic effects to your nervous system: eg. – fentanyl or methadone.
Low doses of drugs which have an opposing mechanism of action to opioids (called opioid antagonists), or specific NMDA (N-methyl-D-aspartate; a special amino acid implicated in opioid sensitivity) antagonists (such as ketamine) may be appropriate in some cases. Your doctor will be able to provide you with more information about this.
High levels of water intake is also recommended for your well-being.


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