Extended-release Gabapentin for Failed Back Surgery Syndrome

Results From a Randomized Double-blind Cross-over Study

Jennifer S. Gewandter; Maria E. Frazer; Xueya Cai; Valerie F. Chiodo; Shirley A. Rast; Michelle Dugan; Hudson A. Carter; Redi Rahmani; Jonathan J. Stone; John D. Markman

Disclosures

Pain. 2019;160(5):1029-1036. 

In This Article

Abstract and Introduction

Abstract

Persistent pain after lumbar surgery (failed back surgery syndrome [FBSS]) remains a leading indication for chronic analgesia. However, no analgesics have proven efficacious for this condition. Although trials have evaluated gabapentinoids for chronic low back pain, none of these trials focused solely on FBSS. This randomized, double-blind cross-over trial evaluated the efficacy of gabapentin (1800 mg/day) for FBSS. Eligible patients had a diagnosis of FBBS, an average daily pain score of at least 4 of 10, a neuropathic pain component (indicated by the PainDetect), and reported at least half of their pain radiating in their lower extremity. Participants were randomized to 2, 7-week study periods separated by a 10-day washout. The primary outcome measure was a 0 to 10 numeric rating scale (NRS) of average pain. Secondary measures included the McGill Pain Questionnaire and Patient Global Impression of Change. The treatment effect was analyzed using a mixed effect analysis of covariance with fixed effects for treatment, period, and baseline 7-day mean NRS pain score and a random effect for the participant. The outcome of the model was the mean 7-day NRS score for the last 7 days of each treatment period. Thirty-two participants were randomized and included in the primary analysis; 25 completed both study periods. No difference was detected between treatments on any outcome measure, including the primary (least square mean difference in NRS: −0.01 confidence interval: [−0.22 to 0.20]). Given the escalating rate of complex lumbar surgery, future research to develop novel therapies for this prevalent syndrome is needed.

Introduction

The number of spine surgeries in the United States has tripled over the past 20 years.[1] Persistent pain after lumbar surgery remains a leading indication for subspecialty pain management referral and chronic analgesic use. Growth in the proportion of fusion surgery relative to the total number of spine operations (eg, laminectomy and discectomy) is associated with a rise in operative revisions for chronic pain and other complications.[18] Recent studies find that rates of long-term opioid use are higher after spine surgery for the indication of chronic low back pain than before these procedures.[5] The increased rates of analgesic prescribing reflect high residual levels of pain intensity and functional limitation in this postsurgical population.

The relative contribution of neuropathic and inflammatory mechanisms to chronic low back pain syndromes is unknown.[3,17] The complexity of determining a causative pathoanatomical lesion and characterizing the pathophysiology of pain is greater in patients with failed back surgery syndrome (FBSS). Unlike the indication for an initial spine surgery, for which a focal anatomical lesion such as a disk protrusion or fracture of the pars is identified, the motive for subsequent surgeries is often a search for the cause of ongoing pain and therefore is frequently characterized as "exploratory." Moreover, there are multiple aspects of the original perioperative course (eg, muscle retraction, electrocautery, incisions, and subsequent scar tissue formation) that may give rise to sources of neuropathic pain. Putative causes such as epidural adhesions causing traction of lumbar nerve roots are routinely hypothesized, but clinical studies have found that these imaging findings lack sensitivity and specificity.[2]

Multiple recent studies of gabapentinoids for chronic low back pain syndromes have been conducted; however, none of these included only a postsurgical population.[20] The questionable efficacy of gabapentinoids in low back pain syndromes and the increasing appreciation for their risks has led to concern about potential overuse of this drug class in chronic low back pain.[25] Thus, further evaluation of gabapentinoids in patients with prior lumbar surgery is warranted.[10] Here, we describe the first analgesic study conducted exclusively in the FBSS population. We hypothesized that the augmented role of neuropathic mechanisms in this important postsurgical chronic low back pain subgroup would increase the likelihood of demonstrating an analgesic and functional benefit.

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