Gabapentin is prescribed for
analgesia in chronic
low back pain, yet there are no controlled trials supporting this practice. This randomized, 2-arm, 12-week, parallel group study compared
gabapentin (forced titration up to 3600 mg daily) with inert placebo. The primary efficacy measure was change in
pain intensity from baseline to the last week on treatment measured by the Descriptor Differential Scale; the secondary outcome was disability (Oswestry Disability Index). The intention-to-treat analysis comprised 108 randomized patients with chronic
back pain (daily
pain for ≥6 months) whose
pain did (43%) or did not radiate into the lower extremity. Random effects regression models which did not impute missing scores were used to analyze outcome data.
Pain intensity decreased significantly over time (P < 0.0001) with subjects on
gabapentin or placebo, reporting reductions of about 30% from baseline, but did not differ significantly between groups (P = 0.423). The same results pertained for disability scores. In responder analyses of those who completed 12 weeks (N = 72), the proportion reporting at least 30% or 50% reduction in
pain intensity, or at least "Minimal Improvement" on the Physician Clinical Global Impression of Change did not differ significantly between groups. There were no significant differences in
analgesia between participants with radiating (n = 46) and nonradiating (n = 62)
pain either within or between treatment arms. There was no significant correlation between
gabapentin plasma concentration and
pain intensity.
Gabapentin appears to be ineffective for
analgesia in chronic
low back pain with or without a radiating component.