What Causes Hyperalgesia? Types & Treatment

Medically Reviewed on 11/11/2021
what causes hyperalgesia
Hyperalgesia is a condition in which you develop an increased sensitivity to pain, often caused by bodily injury or opioid use

Hyperalgesia is a condition in which you develop an increased sensitivity to pain.  Hyperalgesia is believed to be the result of an allergic or inflammatory response. When immune system cells interact with the peripheral nervous system, pain-inducing chemicals are released, which increase the responsiveness of nerve receptors.

Hyperalgesia can be caused by various medical conditions, including:

Long-term opioid (heroin and morphine) use can lead to hyperalgesia and pain out of proportion to physical findings, which is a common cause of the loss of efficacy of these medications over time. 

Because it can be difficult to distinguish from tolerance, opioid-induced hyperalgesia is frequently treated by increasing the dosage, potentially exacerbating the problem by increasing sensitivity to pain.

What are different types of hyperalgesia?

People with hyperalgesia experience excruciating pain even when an injury or medical condition has not worsened. This pain may worsen over time and spread to other parts of the body, evolving into a new or distinct type of pain. 

  • Opioid-induced hyperalgesia: Increased pain sensitivity after using opioids such as heroin, morphine, or fentanyl. Opioids are commonly used as analgesics. However, high doses can have the opposite effect and increase pain.
  • Injury-induced hyperalgesia: Increased pain response caused by a tissue or nerve injury and sometimes experienced after surgery. It can be divided into two subtypes:
    • Primary hyperalgesia is characterized by intense pain in the vicinity of the injured body part.
    • Secondary hyperalgesia occurs when pain appears to spread from the injured area to other parts of the body.

Because there is no standard method for detecting hyperalgesia, diagnosis can be difficult. Typically, your doctor will assess your symptoms, medical history, and medications. They may conduct a physical examination to look for recent injuries or underlying diseases.


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What are treatment options for hyperalgesia?

Hyperalgesia is a treatable condition that may respond to standard treatment.

  • Reducing opioid dose over time: If your hyperalgesia is caused by opioid use, your doctor may instruct you to gradually reduce your opioid dose. Because of the lengthy treatment period, you may experience severe pain and opioid withdrawal symptoms. However, your doctor can assist you in managing your symptoms.
  • Switching to other opioid medications: Your doctor may prescribe smaller doses of a different opioid. Opioids such as methadone, oxycodone, and tramadol are effective in the treatment of opioid-induced hyperalgesia.
  • Using N-methyl-D-aspartate (NMDA) receptor antagonist drugs: According to some studies, NMDA receptors increase your pain sensitivity. NMDA receptor antagonists are medications that block pain receptors and suppress pain responses. Ketamine and methadone are two common NMDA receptor antagonists used to treat hyperalgesia.
  • Other medications: Hyperalgesia is similar to medical conditions caused by nerve irritation or damage. As such, it may respond to medications such as selective serotonin reuptake inhibitors, tricyclic antidepressants, nonsteroidal anti-inflammatory drugs, glucocorticoids, gabapentin, or pregabalin.

Treatment of hyperalgesia can be clinically challenging, and finding an effective drug or drug combination for a specific person may require trial and error. The use of a transcutaneous electrical nerve stimulation device may also alleviate hyperalgesia.

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Medically Reviewed on 11/11/2021
Image Source: iStock Images

A comprehensive review of opioid-induced hyperalgesia: https://pubmed.ncbi.nlm.nih.gov/21412369/

Models and Mechanisms of Hyperalgesia and Allodynia: https://journals.physiology.org/doi/full/10.1152/physrev.00025.2008

Hyperalgesia: An Emerging Iatrogenic Syndrome: https://www.jpsmjournal.com/article/S0885-3924(03)00258-6/fulltext