Why Opioids Can Stop Working

By Drs. David Niesel and Norbert Herzog The epidemic of opioid abuse and the resulting increases in overdoses and deaths have been front and center in the news for quite some time. Now a little appreciated effect called hyperalgesia, an increased sensitivity to pain, can make these drugs less effective for chronic pain leading people to take higher and higher doses seeking relief, increasing the chance of addiction. Opioids can actually prolong and amplify pain rather than relieving it. Opioids are pain relieving drugs that include hydrocodone, oxycodone, morphine, codeine and other related drugs including illegal ones such as heroin. They are prescribed to relieve pain from a variety of conditions. Opioids act by binding to proteins called opioid receptors located in the brain, spinal column, digestive tract and other organs. Once attached to these receptors, they reduce the perception of pain. However, they can cause drowsiness, nausea, constipation and mental confusion but can also dangerously depress respiration at higher doses. Surprisingly, opioids can remodel the nervous system to amplify pain signals even after the original injury has healed leaving animals more sensitive to pain. Similarly, people who take opioids prior to surgery typically experience more pain. In an attempt to understand this hyperalgesia and the role of the immune system in it, scientists used an animal model of chronic pain as the result of traumatic nerve injury. Control animals underwent a ...
Source: Science - The Huffington Post - Category: Science Source Type: news