World's largest opioid review finds they often don't work

Researchers from the University of Sydney led the investigation, which examined the effectiveness and safety of opioid medications such as codeine, morphine, oxycodone, and tramadol. The analysis brought together evidence from 59 systematic reviews covering more than 50 acute pain conditions affecting both children and adults.

Published in the journal Drugs, the review offers the most comprehensive assessment to date of where opioids help, where they do not, and where evidence remains limited.

"Opioids are among the most commonly prescribed treatments for acute pain, however, our review found that they did not provide large or lasting pain relief compared with placebo for the vast majority of acute pain conditions, with pain relief typically lasting only a few hours," said lead author Associate Professor Christina Abdel Shaheed, from the School of Public Health at the University of Sydney.

"Overall, oral opioids were only slightly better than placebo for acute musculoskeletal pain, which they are often prescribed for, in the six to 48 hours after starting treatment. Opioids also increased the risk of side effects when used for acute musculoskeletal pain, some types of post-surgical pain or traumatic limb pain.

"By showing that the benefits are generally small, short-lived, absent for many common conditions, and sometimes harmful, our research challenges the widely held belief that opioids are the most effective 'go-to' option for acute pain."

Where Opioids Help and Where They Don't

The researchers found that opioids can provide modest, short term pain relief for certain acute conditions. These include stomach pain, pain after dental surgery, ear procedures, traumatic limb injuries, childbirth, caesarean delivery, and bunionectomy (bunion removal).

However, the medications showed no advantage over placebo for several other conditions. These included some types of limb surgery, kidney stone pain, pain following tonsil removal, and pain experienced by newborns using assisted breathing devices.

The review also found inconsistent benefits over time for heart related pain, pain after hysterectomy (removal of a woman's uterus), and topical opioid treatments (patches) used for dermatological (skin) pain.

Side Effects and Safety Concerns

In addition to their limited effectiveness, opioids were linked to a higher risk of side effects in several situations, including acute musculoskeletal pain, traumatic limb injuries, and some forms of post surgical pain. Common side effects included nausea and vomiting.

The researchers noted that while very short term opioid use can reduce pain for certain acute conditions, regular use carries important risks. These include tolerance, dependence, misuse, overdose, hospitalization, and death.

The study also highlighted concerns about the quality of available safety data. According to the authors, many clinical trials did not adequately report side effects, suggesting that the true risks associated with opioid use may be greater than currently documented.

Overall, the evidence does not support routine opioid use for acute pain. The researchers also pointed out that some studies evaluated only single doses, which may not accurately reflect how these medications are used in everyday medical practice.

Risk of Dependence Can Develop Quickly

"Persistent use of opioid medicines can develop quickly following first time use (sometimes within days), and may arise from regular use for acute pain," said co-first author Dr. Stephanie Mathieson from the University of Sydney's Institute for Musculoskeletal Health and School of Pharmacy.

"It is important that patients are informed about the potential harms from opioids when prescribed them, and that doctors prescribe these medicines judiciously (lowest effective dose for the smallest amount of time) for acute pain," she said.

Co-first author Associate Professor Joshua Zadro from the University's Institute for Musculoskeletal Health and School of Health Sciences said the findings have broad implications.

"These findings are important for patients across all age groups who experience acute pain, doctors treating these conditions and policy makers who regulate the safe use of these medicines in the community."