Opioids have long been the cornerstone of acute pain management, however, long-term adverse effects are known to occur with prolonged use. Opioid tolerance (increased dose needed for analgesia) and opioid-induced hyperalgesia (paradoxical increase in pain with opioid administration) results in poorly controlled pain and dose escalation. While the precise mechanism for OIH is not fully understood, it is likely the result of multifactorial changes, and the impact of opioid exposure on the descending modulatory system suggests important mechanisms for targeted prevention and treatment.
Historically, the phenomenon of OIH has been described as early as the 19th century. In 1870, the physician Clifford Allbutt described the phenomenon stating, “at such times I have certainly felt it a great responsibility to say that pain, which I know is an evil, is less injurious than morphia, which may be an evil. Does morphia tend to encourage the very pain it pretends to relieve?”
