Codeine for Acute Pain in Patients Undergoing Orthopedic Surgery: A Review of Clinical Effectiveness [Internet]

Excerpt

Orthopedic (i.e., musculoskeletal) surgery, as with most surgical procedures, can bring about inflammation, tissue injury (e.g., mechanical, thermal, chemical), or nerve injury (e.g., transection, stretching, compression). These three noxious stimuli cause specialised sensory nerves located almost everywhere in the body, called nociceptors, to send an impulse along their nerve fiber to the dorsal horn of the spinal cord which then relays the signal to neurones projecting to the brain.^, As the signal ascends and reaches the brain, it is distributed to various central structures where it can be processed further. Although the physiology of pain is elaborate and poorly understood, it is thought that at this point in transmission, pain becomes a conscious experience, and subject to modulation by many additional factors such as chemical mediators of pain, the endogenous opiate system, and other domains such as a person’s personality, circumstances, and emotional state. Pain can be classified as acute (lasting for minutes to several weeks), or chronic (lasting months to years).^, This report will focus on acute pain as a result of orthopedic surgery.

The goals of therapy for postoperative acute pain include the recognition that the patient is experiencing pain, to anticipate and pre-emptively relieve the pain, to rapidly reduce the intensity of the pain, and to generally minimise discomfort.^,– Treatment should be continued as long as the patient is experiencing pain.

Typically, therapeutic options for orthopedic postoperative pain control are multimodal and tailored to the patient’s characteristics, their needs, and the level of pain associated with the surgery. These factors will determine the type of analgesic technique (systemic, regional, local), as well as the category of pharmacotherapy (e.g., opioid, non-opioid) that should be privileged. Opioids (e.g., morphine, fentanyl, hydromorphone, oxycodone, codeine) are the most widely used treatment of postoperative pain;^, however, non-opioids (e.g., non steroidal anti-inflammatory drugs, acetaminophen, salicylates) can also be used.^,

This being said, opioid prescribing practices have come under scrutiny in recent years as Canada battles with an opioid epidemic. Overprescribing by physicians,^– and the diversion of non-consumed supplies, have been recognised as a contributor to the national opioid epidemic. As a result there has been a desire to optimize opioid prescribing after surgery, when patient and surgical factors make this possible. Specifically, the role of codeine in orthopedic post-operative pain management is being questioned and will be the focus of the present report.

In Canada, several formulations of codeine are available for treatment of pain. Codeine primarily agonises the mu receptor.^, It is metabolised in the liver by the cytochrome P450 system, specifically via the CYP2D6 isoenzyme, to various metabolites including morphine,^, which accounts for some of its analgesic effect.^,, The rate of metabolism by the CYP2D6 isoenzyme is known to vary in the general population,^, which highlights the variety of pain relief that can been observed when codeine is used as a single agent. It is a relatively weak opioid, and may also be used in combination with acetaminophen, where an additive analgesic effect is seen.

A previous CADTH report, published in 2010, sought clinical effectiveness and guideline evidence on pre-hospital orthopedic injury or fracture pain management. The objective of the present report is to investigate the clinical effectiveness of codeine or codeine with acetaminophen for the management of acute pain in adults post orthopedic surgery.