Common medications can prolong back pain, study finds

The very medications often used to relieve pain in the lower back, which the Centers for Disease Control and Prevention says is the most common type of pain, can cause the pain to linger, a new study has found.

Persistent use of analgesic steroids and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen can actually convert pain from a sprained back into a chronic condition.

Some medical experts have recommended caution in interpreting the results. The study did not use the gold standard in medical research, which would be a clinical trial in which people with back pain were randomly assigned to take a nonsteroidal anti-inflammatory drug or a placebo and followed up to see who would go on to experience chronic pain. Instead, it involved observation of patients, an animal study, and an analysis of patients in a large database.

“It’s interesting, but requires further study,” commented Steven J. Atlas, director of general practice-based research and quality improvement at Massachusetts General Hospital.

Bruce M. Vrooman, a pain specialist at Dartmouth Hitchcock Medical Center in New Hampshire, agreed, but found the study “impressive for its scope” and said that if its results are confirmed with a clinical trial, it “may compel us to review how we treat acute pain”.

Thomas Buchheit, director of the regenerative pain therapies program at Duke University, had a different reaction.

“People abuse the term ‘paradigm shift,’ but this is a paradigm shift, without a doubt,” he opined. “There is a rule that is not made explicit: if it hurts, take an anti-inflammatory. If it still hurts, add a steroid.” But, he said, the study shows “that we need to think about healing, not suppressing inflammation.”

Guidelines from associations of medical professionals already provide that people with back pain should start with non-drug treatments such as exercise, physical therapy, heat treatment or massage. These measures are as effective as painkillers, without causing the same side effects.

If pain persists, the guidelines say, people can try nonsteroidal anti-inflammatory drugs like ibuprofen (acetaminophen is not an anti-inflammatory because it does not block inflammation).

But the study, published in the journal Science Translational Medicine, included a warning that such advice on medication use can contribute to chronic pain that will reduce a person’s quality of life.

The study began when researchers at McGill University began looking for molecular markers in the blood that could predict which patients would have pain that would subside in a short time and which would have persistent pain.

The group had blood samples from 98 people taken when they first reported having back pain and again three months after the pain started.

“What we saw was not quite what we expected,” said Luda Diatchenko, the study’s principal investigator and a professor at McGill University who specializes in the genetics of human pain.

People who said their pain disappeared had rapid, intense inflation with sharp pain. Then the inflammation markers decreased over the next three months. Those whose pain persisted did not have this inflammatory reaction.

“Absolutely nothing happened” to people with chronic pain, Diatchenko said. “It was a huge difference.”

The researchers continued to investigate. They studied people with a different type of pain, TMD, or temporomandibular disorders, which cause jaw pain. Again, people who recovered had rapid and intense inflammatory responses.

The researchers replicated the findings in mice, compressing the animals’ sciatic nerves to cause back and leg pain and injecting the sciatic nerves with an irritant. When they blocked the animals’ immune response with dexamethasone, a corticosteroid commonly used to treat back pain, the pain became chronic.

The group then asked whether the chronic pain resulted from pain suppression or inflammation suppression. A prescription anti-inflammatory, diclofenac, was given to some mice. Other mice were given one of three other pain relievers: gabapentin, morphine and lidocaine.

The pain only persisted, becoming chronic, with diclofenac.

These results led them to ask: Are patients who take nonsteroidal anti-inflammatory drugs like ibuprofen or corticosteroids like dexamethasone to relieve their back pain more likely to develop chronic pain?

The researchers sought data from the UK Biobank, a repository containing information on the conditions and drug use of around half a million patients. They studied 2,163 people with acute back pain, 461 of whom eventually progressed to chronic pain. Those who took a nonsteroidal anti-inflammatory drug were almost twice as likely to develop chronic back pain as those who took any other drug or none at all.

Diatchenko doesn’t think what he found has anything to do with opiate addiction. In fact, she said, “to avoid opiates, doctors started prescribing more NSAIDs.”

The tendency to use nonsteroidal anti-inflammatory drugs persists despite their less than stellar performance. A review of randomized controlled trials found that these drugs have almost no benefit in reducing low back pain when compared with placebos.

Atlas said anti-inflammatories use is likely not harmful in the short term, but the new study, while not proving that long-term use is harmful, “at least reveals a biological mechanism that says short-term use is not harmful.” is the same as the long term”.

James N. Weinstein, senior vice president of health at Microsoft, would like people to rethink their instinct to reach for ibuprofen pills and opt for exercise instead, counterintuitive as that may seem.

He, who for 28 years was editor-in-chief of the medical journal Spine and was not involved in the new study, said that when he has a backache, he goes for a run. And that relieves his pain.

“I really enjoyed it,” he said, speaking of the study, “and I know it’s true.”

_{Translation by Clara Allain}