science

Opioid-induced hyperalgesia

Opioid-induced hyperalgesia is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Opioid-induced hyperalgesia rather than just read about it. In short: Opioid-induced hyperalgesia (OIH) or opioid-induced abnormal pain sensitivity, also called paradoxical hyperalgesia, is an uncommon condition of generalized pain caused by the long-term use of high dosages of opioids such as morphine, oxycodone, and methadone. OIH is not necessarily confined to the original affected site.

Key takeaways

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Learn the definition first, then one example that makes the definition concrete.
Connect Opioid-induced hyperalgesia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Opioid-induced hyperalgesia from memory before moving on to harder problems.

Reference excerpt

Opioid-induced hyperalgesia (OIH) or opioid-induced abnormal pain sensitivity, also called paradoxical hyperalgesia, is an uncommon condition of generalized pain caused by the long-term use of high dosages of opioids such as morphine, oxycodone, and methadone. OIH is not necessarily confined to the original affected site. This means that if the person was originally taking opioids due to lower back pain, when OIH appears, the person may experience pain in the entire body, instead of just in the lower back. Over time, individuals taking opioids can also develop an increasing sensitivity to noxious stimuli, even evolving a painful response to previously non-noxious stimuli (allodynia). This means that if the person originally felt pain from twisting or from sitting too long, the person might now additionally experience pain from a light touch or from raindrops falling on the skin. OIH differs from drug tolerance, although it can be difficult to tell the two conditions apart. OIH can often be treated by gradually tapering the opioid dose and replacing opioid-based pain care with other pain management medications and techniques or by opioid rotation. In a 2012 study, 39 patients had abdominal pain and OIH. They underwent detoxification and almost all of those patients "were able to stop using narcotics and have significant improvement in pain."

Differentiation from tolerance Tolerance, another condition that can arise from prolonged exposure to opioids, can often be mistaken for opioid-induced hyperalgesia and vice versa, as the clinical presentation can appear similar. Although tolerance and opioid-induced hyperalgesia both result in a similar need for dose escalation to receive the same level of effect to treat pain, they are nevertheless caused by two distinct mechanisms. The similar net effect makes the two phenomena difficult to distinguish in a clinical setting. Under chronic opioid treatment, a particular individual's requirement for dose escalation may be due to tolerance, opioid-induced hyperalgesia, or a combination of both. In tolerance, there is a lower sensitivity to opioids, theorized to occur via two major mechanisms: decreased receptor activation (desensitization of antinociceptive mechanisms) and opioid receptor down-regulation (internalization of membrane receptors). In opioid-induced hyperalgesia, sensitization of pronociceptive mechanisms occurs, resulting in a decrease in the pain threshold, or allodynia. In addition, what appears to be opioid tolerance can be caused by opioid-induced hyperalgesia lowering the baseline pain level, thus masking the drug's analgesic effects. Identifying the development of hyperalgesia is of great clinical importance since patients receiving opioids to relieve pain may paradoxically experience more pain as a result of treatment. Whereas increasing the dose of opioid can be an effective way to overcome tolerance, doing so to compensate for opioid-induced hyperalgesia may worsen the patient's condition by increasing sensitivity to pain while escalating physical dependence. This "uncommon but important phenomenon [can be] seen with high-dose opioid therapy." However, the conclusion of a report published in the Journal of Pain and Palliative Care Pharmacotherapy suggests that "[h]yperalgesia shares a common mechanism with tolerance and it may be that hyperalgesia is a manifestation of tolerance itself."

Pharmacology

The pharmacology of opioids involves the substance binding to opioid receptors in the nervous system and other tissues. The three known and defined opioid receptors are mu, kappa and delta, with many other receptors reported as well. These receptors are notable for binding opioids and eliciting an analgesic response, thus alleviating the sensation of pain. The mu opioid receptor is targeted most often by opioids to relieve pain. Two of the most commonly used opioid antagonists at the mu receptor are naltrexone and naloxone. The pharmacology for opioid-induced hyperalgesia is more complicated, and is believed to involve the activation of NMDA receptors and increased excitatory peptide neurotransmitters (such as cholecystokinin).

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Opioid-induced hyperalgesia

Start with the simplest possible case. Write down what Opioid-induced hyperalgesia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Opioid-induced hyperalgesia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Opioid-induced hyperalgesia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Opioid-induced hyperalgesia

In research: Opioid-induced hyperalgesia appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Opioid-induced hyperalgesia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Opioid-induced hyperalgesia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Opioids, Pain, so understanding it makes those chapters shorter.
In everyday life: Look for Opioid-induced hyperalgesia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Opioid-induced hyperalgesia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Opioid-induced hyperalgesia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Opioid-induced hyperalgesia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Opioid-induced hyperalgesia in simple terms?

Why does Opioid-induced hyperalgesia matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Opioid-induced hyperalgesia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Opioid-induced hyperalgesia.