4 July 2018

Rethink anticonvulsants for low back pain

Drugs Pain Research

A five-fold increase in the prescribing of anticonvulsant drugs for back and neck pain over the last decade is misguided, with new research firmly showing they have no benefit and the potential for harm.

Drug treatments for low back pain have attracted growing attention, as an opioid crisis rips through the US and other countries, and an increasing number of people suffer pain and disability with the condition. 

But as clinicians turn from opioid prescribing, they may be replacing it with another, equally ineffective, option. 

“Our research shows that anticonvulsants are not effective for low back pain and can lead to more unwanted effects,” Associate Professor Christine Lin, one of the lead authors of a new systematic review into the drugs, said.

The Australian researchers reviewed nine randomised, placebo-controlled trials and found high and moderate quality evidence that the drugs were ineffective for chronic low back pain and lumbar radicular pain. 

In fact, they found that compared with placebo, patients taking gabapentin or pregabalin were 40% more likely to experience adverse effects, most commonly drowsiness, dizziness and nausea. 

One topiramate study also suggested that drug had a sedative effect.

Suicidal ideation and drug misuse had also been reported, Professor Lin said. 

Despite this, the prescribing rate of nerve pain medicines such as anticonvulsants grew from 12 per 1000 spinal pain problems encountered by Australian GPs to 76 per 1000 between 2005 and 2014, Professor Lin, who is Principal Research Fellow at the University of Sydney’s Faculty of Medicine and Health, said. 

This was largely driven by an uptake in pregabalin use. Prescriptions for pregabalin jumped from 1.3 million in the year leading up to March 2014, to 3.7 million in the year leading up to June 2017.

As a result, the anticonvulsant drug now costs the Australian government around $160 million a year, making it one of Australia’s most expensive medications. 

Professor Lin said the “astounding” growth in the popularity of pregabalin may have come from a desire to avoid opioids, which has coincided with the 2013 PBS listing of the drug for neuropathic pain. “Clinicians want to be able to provide patients a treatment and patients want to receive a treatment from their clinician,” she said. 

“Being the new kid on the block, coupled with heavy industry marketing, I think were responsible in driving up the prescription rates as well.”   

While guidelines recommend non-pharmacologic approaches, options such as physiotherapy are often more expensive and less accessible to patients. 

Australian and UK guidelines do not currently mention anticonvulsants as a treatment option for low back pain, while the US says there is insufficient evidence for their use.

This study does, however, raise questions about UK guidelines which support treating sciatica patients with gabapentinoids, in line with neuropathic pain conditions.

While it had no impact on disability, the researchers did find moderate quality evidence that topiramate had a small clinical benefit for pain over the short-term.