In summary, for patients who received anticonvulsants:

Benefits in NNT

    No one was helped
    No one was helped

Harms in NNT

    16% more were harmed (adverse events)
    1 in 6 were harmed (adverse event)

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Source: Enke O, New HA, New CH, Mathieson S, McLachlan AJ, Latimer J, et al. Anticonvulsants in the treatment of low back pain and lumbar radicular pain: a systematic review and metaanalysis. CMAJ. 2018;190(26):E786-E793.

Study Population: 9 trials comprising 859 total adults with low back pain with or without radiation to the leg, sciatica, or neurogenic claudication of any duration

Efficacy Endpoints: Reduction in pain or disability in the immediate-, short-, intermediate-, and long-term

Harm Endpoints: Adverse events

Narrative: Low back pain is a common cause of presentation to the emergency department, comprising over 4% of all presentations.1 Globally, low back pain was found to rank highest in disability and sixth overall in disease burden, with a prevalence of 9.4%.2 However, the majority of episodes do not require a surgical intervention and are treated conservatively with medical therapy.3 While clinical guidelines generally recommend nonpharmacologic interventions and nonopioid analgesics,4 one large study found that the prescription of anticonvulsant medications has nearly doubled from 2000 to 2010.5 However, it is important to determine whether these medications are safe and effective for use in this patient population.

The systematic review discussed here included 9 randomized parallel and crossover controlled trials (859 subjects in aggregate) investigating the efficacy of anticonvulsants compared with placebo in adults with nonspecific low back pain with or without radiation to the leg, sciatica, or neurogenic claudication of any duration.6 The systematic review excluded studies investigating patients who were pregnant, post-surgical, or who had mixed conditions (e.g. low back pain and neck pain). Outcomes included pain intensity, disability, and adverse events. Pain and disability were assessed at the following time points: immediate (≤2 weeks after randomization), short-term (2 weeks to 3 months), intermediate-term (3 to 12 months) and long-term (≥12 months).

Seven trials evaluated a gabapentinoid (e.g. gabapentin, pregabalin), and 2 evaluated topiramate. The mean age of participants was 50.8 years in the treatment group and 51.5 years in the placebo group. Four trials recruited participants with chronic low back pain with or without radiating leg pain and 5 trials recruited participants with lumbar radicular pain. Only 1 trial included participants with acute symptoms.

There was no difference in pain scores in the short-term, intermediate-term, or long-term endpoints among the included studies (moderate to high quality evidence). Gabapentinoids also did not reduce the risk of disability (based on validated disability scales) in study participants (moderate quality evidence). However, there was an increased rate of adverse events in the treatment group (53.0% vs 36.7%; pooled relative risk: 1.4, 95% CI, 1.2 to 1.7; absolute risk difference: 16.3%; Number-needed-to-harm [NNH] of 6; high quality evidence). The most common adverse events reported in participants taking a gabapentinoid were drowsiness or somnolence, dizziness, and nausea. The most common adverse events reported in participants taking topiramate were paresthesias, drowsiness or somnolence, dizziness, and diarrhea.

Caveats: While this meta-analysis found that anticonvulsants did not improve pain or disability, there are several limitations that must be considered. First, while most studies included gabapentinoids, the dose and frequency varied significantly within the included trials. Additionally, there was limited data on topiramate, so it remains unclear whether this medication is effective in this population and further studies are needed. The populations also varied with regard to the underlying pathology and inclusion criteria. Of note, some studies required radiographic imaging to exclude underlying pathology, while others relied exclusively on clinical criteria. Moreover, the time periods varied with regard to the chronicity of the symptoms. This is important because chronic back pain is associated with worse outcomes than acute back pain.7 While most studies evaluated chronic back pain, Maher et al included predominately acute (i.e., less than 3 months duration) back pain patients and also found no difference in pain or disability in their study.8 Finally, there were differences in the pain assessment endpoints in the study groups. As a result, many of the assessments included relatively smaller groups.

Based on the above data, this analysis suggests that gabapentinoids are associated with an increased risk of adverse events without an improvement in pain or disability. We have therefore assigned a color recommendation of Red (Harm > Benefits) to this intervention.

The original manuscript was published in Academic Emergency Medicine as part of the partnership between TheNNT.com and AEM.

Author: Michael Gottlieb, MD, RDMS; Alex Koyfman, MD; Brit Long, MD
Supervising Editor: Shahriar Zehtabchi, MD

Published/Updated: February 3, 2020

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
  2. Tip content...