A study published this month in Science Translational Medicine suggests that a commonly prescribed pain-management treatment may actually lead to chronic back pain, Gina Kolata reports for the New York Times.

Cheat sheets: Evidence-based medicine 101

Study details and key findings

Professional medical societies follow a set of pain-management guidelines that recommend people with back pain first try nondrug treatments like exercise, physical therapy, heat or massage. "Those measures turn out to be as effective as pain-suppressing drugs, without the same side effects," Kolata writes.

However, if the pain does not go away, the guidelines recommend nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen to help manage the pain—a recommendation that could cause chronic back pain, according to the new study.

Earlier this month, researchers at McGill University drew blood samples from 98 participants to look for molecular markers that would predict which individuals would have persistent pain and which would have pain that quickly dissipated.

The researchers drew blood from each participant when they first reported developing back pain and three months after their pain began.

"What we saw wasn't exactly what we expected," said Luda Diatchenko, the study's principal investigator and a professor at McGill who specializes in human pain genetics.

The participants who said their pain went away had rapid and severe inflammation when their pain was acute, Kolata writes. Among those participants, inflammation markers diminished over the next three months. Meanwhile, participants whose pain persisted did not show the same inflammatory reaction.

"Absolutely nothing was happening" for participants with chronic pain, Diatchenko said.

"It was a huge difference," she added.

The researchers also studied people with temporomandibular joint disorders (TMJ), which cause jaw pain. Similarly, participants who recovered quickly had rapid and severe inflammatory responses.

Notably, the researchers also replicated these findings in mice. To trigger back and leg pain, they compressed the animals' sciatic nerves or injected the sciatic nerves with an irritant. According to Kolata, when they blocked the mice's immune response with dexamethasone—a steroid that is commonly used to treat back pain—the pain became chronic.

The researchers questioned whether chronic pain stemmed from pain suppression or inflammation suppression. However, they found that the pain only became chronic with a prescription anti-inflammatory called diclofenac.

Those findings led them to question whether patients who took NSAIDs like ibuprofen or steroids like dexamethasone to relieve their back pain were also more likely to develop chronic pain.

To answer this question, they analyzed data from the UK Biobank. Specifically, they studied 2,163 people with acute back pain. Of those, 461 developed chronic pain. Ultimately, the researchers found that individuals who were taking NSAIDs almost doubled their chance of developing chronic back pain compared with those taking other drugs or no drugs.

Commentary

Steven Atlas, director of primary care practice-based research and quality improvement at Massachusetts General Hospital, said that short term use of NSAIDs is not likely to be harmful. And while he said the new study does not provide definitive proof that long term use is harmful, it "at least gives a biological mechanism that says short term use is not the same as long term."

Still, several medical experts warned against interpreting the results too broadly. Diatchenko said she does not believe the study's findings are relevant to the issue of opioid addiction.

In addition, according to Kolata, "[t]he study did not use the gold standard for medical research, which would be a clinical trial in which people with back pain would be randomly assigned to take a nonsteroidal anti-inflammatory drug or a placebo and followed to see who developed chronic pain. Instead, it involved observations of patients, an animal study and an analysis of patients in a large database."

"It's intriguing but requires further study," Atlas said.

Similarly, Bruce Vrooman, a pain specialist at Dartmouth Hitchcock Medical Center, agreed, while calling the study "impressive in its scope" and noting that if the results hold up in a clinical trial, it could "force reconsideration of how we treat acute pain."

However, Thomas Buchheit, director of the regenerative pain therapies program at Duke University, presented a different view.

"People overuse the term 'paradigm shift', but this is absolutely a paradigm shift," Buchheit said. "There is this unspoken rule: If it hurts, take an anti-inflammatory, and if it still hurts, put a steroid on it," he added. "But," he said, this study signals that "we have to think of healing and not suppression of inflammation." (Kolata, New York Times, 5/14)