Hyperalgesia is defined as an increased sensitivity to pain. Opioid-induced hyperalgesia (OIH) is defined as a state of sensitization caused by the exposure to opioids. OIH is distinguishable whereby a patient who receives opioids to help with chronic pain can actually become more sensitive to pain. It can be the same pain as the patient is taking opioids to relieve or it could be a completely different pain in a new location. Due to an increased usage of opioids in chronic pain patients, OIH is becoming a great concern in the medical field. Something that would not normally cause pain, may cause a high rate of pain and things that normally do cause pain, may cause a significantly worsened pain.
OIH has three main symptoms: an increase in how intense the pain feels, the spreading of the pain from the initial location to other locations, and an increase in the pain that you feel to external stimuli. Physicians may increase the dosage of opioids to help with this increased pain but it can actually make it more severe for those suffering from OIH. OIH is completely different from opioid tolerance. Opioid tolerance occurs when the same dosage of opioids stops relieving the pain as effectively as it once did due to the patient building up a tolerance to opioids. In opioid tolerance, an increase in the dosage usually helps relieve the pain it is prescribed for. Hyperalgesia occurs when certain nerve receptors become more sensitive. When tissue is damaged, the body releases compounds. The compounds enhance the responsiveness of the nerve receptors. This leads to hyperalgesia. Due to trauma to the tissue or nerves at a surgical site, some people may develop hyperalgesia following a surgery. Those suffering from fibromyalgia or shingles may also develop hyperalgesia. OIH can develop in people taking opioids long-term or only taking them for a short period of time. If you are experiencing increased pain while taking opioids, your doctor may suspect OIH.
Treatment usually includes reducing the opioid dosage, tapering off opioids, or supplementing with receptor modulators. A receptor modulator is a substance that acts on a chemical receptor, usually as an agonist, antagonist, or combination of both. An agonist is a muscle that is controlled by the action of an antagonist with which it is paired. Not all patients who take high doses of opioids experience hyperalgesia. Your doctor should rule out any preexisting conditions before diagnosing hyperalgesia. Your medical history should be evaluated, as well as any medications you are taking, before deciding on how to treat your hyperalgesia.