Commonly prescribed drugs for back pain often ineffective, review says

Doctors are prescribing anti-seizure and nerve pain medications for a common type of chronic low-back pain, a non-licensed use, despite a lack of studies supporting their effectiveness for that purpose, according to a new review.

The drugs, known as gabapentinoids, include gabapentin (originally marketed under the brand name Neurontin) and pregabalin (previously sold as Lyrica alone). Health Canada approved gabapentin to treat epilepsy that isn't controlled by conventional therapy, and pregablin is indicated for types of nerve pain. 

Both medications are also prescribed for non-licensed uses, including non-specific chronic lower back pain that doesn't involve nerves in the legs and whose cause can't be traced. About 90 to 95 per cent of adults experience low back pain at some point.

In Tuesday's issue of the journal PLOS Medicine, Dr. Harsha Shanthanna, an anesthesiologist and associate professor in the anesthesia department at McMaster University in Hamilton, and his team analyzed eight randomized controlled trials on use of the drugs among adults with chronic low back pain.

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"There are very few studies that allow physicians to make informed decisions. That's probably one of the most important findings," Shanthanna said in an interview. "Whatever studies do exist do not support its use or do not show a benefit in the form of pain relief."

In 2004, after Neurontin's patent expired, Pfizer admitted to fraudulently marketing gabapentin. In 2012, Pfizer settled over its misleading promotional claims of pregabalin.

The other main finding, Shanthanna said, was that four side-effects were common with these medications:

• Dizziness.
• Fatigue.
• Difficulties with thinking or mental activity.
• Visual disturbances.

Family doctors, neurologists and chronic pain physicians prescribe the medications.

Shanthanna said physicians are thoughtful and careful when choosing pain medications for individual patients, which tends to be based on trial and error. "What we emphasize in our review is we've got to be more cautious."

He called for more research to guide physicians.

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"This should actually make us do more studies so that we can more definitely and more conclusively inform ourselves rather than getting a skewed picture." 

Canada's Patented Medicine Prices Review Board notes that between 2011 to 2013, about one-third of new gabapentin users had used opioids just before switching.

The Canadian site notes increasing misuse of gabapentin, as does Ohio's Substance Abuse Monitoring. In 2014 in England, the National Health Service's advisory warned of misuse potential for both gabapentin and pregabalin, along with suggestions on using the medicines.

Alternatives to drugs needed

Earlier this month, Dr. Christopher Goodman and Dr. Allan Brett of the South Carolina School of Medicine wrote a commentary in the New England Journal of Medicine about increased prescribing of gabapentin and pregabalin for pain.

"We suspect that clinicians who are desperate for alternatives to opioids have lowered their thresholds for prescribed gabapentinoids to patients with various types of acute, subacute, and chronic non-cancer pain," Goodman and Brett wrote.

They said indiscriminate off-label use of gabapentinoids reinforces the tendency of clinicians to view pain treatment through a pharmacologic lens.

Rather, the pair wrote, for clinicians to manage both acute and chronic pain appropriately, they need to spend time assessing how the patient's pain affects their activity and function to mitigate it, not necessarily eliminate it.

But non-pharmacologic approaches, such as cognitive behavioural therapy or referrals to multidisciplinary pain clinics, may be unavailable or unaffordable, they said.