Male doctor assesses male patient for possible hyperalgesia symptoms

Physicians commonly prescribe opioids to treat pain, with more than 17 percent of Americans filling at least one opioid prescription in 2017, according to the Centers for Disease Control and Prevention. Yet few people realize that prolonged use of opioids can actually make pain worse.

A condition called opiate-induced hyperalgesia remains relatively misunderstood by patients and physicians. Here’s what you need to know about hyperalgesia and what you can consider asking your doctor.

What Is Hyperalgesia?

The word “hyperalgesia” means increased (“hyper”) pain (“algesia”). Opiate-induced hyperalgesia is precisely what it sounds like: a condition in which taking opioids causes a person to experience a greater degree of pain.

Read More: What Is Hyperalgesia? Learn the Signs and Symptoms

It is difficult to estimate how many people suffer from hyperalgesia. Experts agree that there isn’t sufficient data to support or refute the condition’s existence and that the quality of available studies on hyperalgesia is poor, according to Practical Pain Management.

Scientists continue to study hyperalgesia, but the exact causes are not yet understood. When a person takes opioids, the opioid molecules bind to special receptors throughout the brain and body. The opioids block pain messages sent to the brain. For some people, after opioids bind, the pain receptors become even more sensitive, meaning as time goes on, even a less-painful stimulus can cause a severe pain response. When this condition develops, the brain receives major pain signals even when the circumstances would normally not be particularly painful.

Why Many Pain Patients Are Unaware of Hyperalgesia

Many pain patients have never heard of hyperalgesia and are unaware of its effects. Part of this lack of awareness may be due to physicians failing to mention the possibility of the condition because they think it’s unlikely in their patients.

According to a report on opioid-induced hyperalgesia by physicians at the Institute of Pain Medicine in Haifa, Israel, evidence to support the notion that opioid dose escalation causes OIH is limited, in part because studies of chronic pain patients have used various experimental pain models yielding inconsistent results that can be hard to interpret. The study noted that the need for pain models to establish the clinical diagnosis of OIH — and the need to indentify which specific model would be preferred — is yet to be determined.

Some medical practitioners simply write a prescription for opioid painkillers without thoroughly explaining every potential risk. Even if they do describe the risks, doctors may focus on the risk of addiction or developing a tolerance to the medication, not hyperalgesia. Thus, patients may not be informed that they could potentially experience greater pain as a result of taking opioid painkillers.

What Is the Difference Between Hyperalgesia and Tolerance?

Another difficulty patients encounter is understanding the difference between hyperalgesia and tolerance. Tolerance is a normal physiological reaction to taking opioid medications over an extended period of time. As your body becomes accustomed to the presence of opioids, your pain receptors can become less responsive to the drug. This means that you may need a higher dose to achieve the same painkilling effects that you used to get from a lower dose.

Many patients understand that developing a tolerance is a possible consequence of taking opioid painkillers. When some start to experience increased pain, however, they might increase their drug dose to compensate for the tolerance. Taking more opioids than prescribed can be dangerous, so pain patients can benefit from regularly communicating any changes in tolerance to their doctors.

Although patients who have developed a tolerance can still get the painkilling effects of opioids at a higher dose, patients experiencing opiate-induced hyperalgesia feel no effect or pain relief by taking more of the drug. Instead, taking more of the opiate could make things worse by causing pain receptors to become even more sensitized. Complicating things further, patients can experience both hyperalgesia and tolerance at the same time. Disentangling these effects can be challenging, making patient-doctor communication even more critical.


Female doctor and female patient discuss how to diagnose and treat opioid-induced hyperalgesia


Why Diagnosing Hyperalgesia Is Important

The lack of studies on opioid-induced hyperalgesia makes it difficult to properly diagnose OIH and means there isn’t data to show how many people are affected by it. And this lack of data means that, even though the condition is a real problem, doctors don’t have evidence or data to make discussing the issue with patients a priority.

The few studies that have been conducted show evidence for hyperalgesia most clearly in patients taking extreme doses, such as opioid abusers and terminal cancer patients with severe pain, according to Science Magazine. Evidence of OIH in patients taking lower doses of opioids over long periods of time, such as when managing chronic pain over months or years, is harder to come by. Variables such as opioid tolerance levels, changes in the underlying condition, or changes in the patient’s chronic pain symptoms complicate diagnosing OIH. Some researchers are working to document changing pain thresholds with quantitative sensory tests to help diagnose OIH, according to Science Magazine.

Risks of Leaving OIH Untreated

Without an abundance of evidence of OIH and a clear method of diagnosing the condition, some doctors remain skeptical of it. Their skepticism can cause them to dismiss a patient’s complaint of excessive pain as exaggeration. Doctors might even mislabel pateints with hyperalgesia as “medication-seeking” if they don’t recognize hyperalgesia as the reason the patients are requesting more drugs.

One of the biggest risks of hyperalgesia going undiagnosed is that physicians might prescribe higher doses of opioid painkillers in an attempt to treat the patient’s pain. This leads to increased risk of developing or worsening an opioid use disorder. Conversely, if a doctor disregards the patient’s complaints of increasing pain as illegitimate, the patient could be at risk of several problems, such as excessive pain or a potential to use or abuse other drugs in an attempt to relieve hyperalgesia symptoms.

How to Recognize Signs of Hyperalgesia to Discuss With a Doctor

Some physicians are misinformed or underinformed about hyperalgesia, so patients have an opportunity to become their own advocates. People taking opioid painkillers can watch for symptoms of opioid-induced hyperalgesia to considering discussing with their doctor. The most common symptoms include:

  • Pain intensity that increases even though the underlying medical condition has not gotten worse
  • The area of pain becomes broader than the initially affected region
  • New pain develops in a different part of the body without