Extended-release gabapentin for failed back surgery syndrome: results from a randomized double-blind cross-over study.

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.

Interpretation of urine drug testing results in patients using transdermal buprenorphine preparations for the treatment of chronic noncancer pain.

OBJECTIVE: To determine whether the prevailing liquid chromatography and tandem mass spectroscopy assay (LC-MS/MS) assay designed to monitor buprenorphine compliance of the sublingual formulation used in the substance abuse treatment setting can be extrapolated to the transdermal formulation used in the chronic pain treatment setting, which is 1000-fold less concentrated. DESIGN: Retrospective chart review. SUBJECTS: Self-reported compliant patients using the transdermal or sublingual formulations of buprenorhphine. Transdermal patch application was also visually confirmed during clinic visits. METHODS: Urine drug test results from a LC-MS/MS were compared between samples from transdermal and sublingual patients. RESULTS: While all sublingual patients tested positive for at least one metabolite of buprenorphine, only 69% of the transdermal patients did so. In addition, the most abundant metabolite in the transdermal patients was buprenorphine-glucuronide, as compared with norbuprenorphine-glucuronide in sublingual patients. CONCLUSIONS: These data suggest that currently available urine drug tests for buprenorphine, including the more expensive LC-MS/MS based assays, may not be sufficiently sensitive to detect the metabolites from transdermal buprenorphine patients. This study highlights the need to evaluate the value and sensitivity of urine drug tests given the wide range of buprenorphine dosing in clinical practice. These results underscore the need for additional cost benefit analyses comparing different confirmatory drug testing techniques including many commercially available drug testing options. © 2014 Wiley Periodicals, Inc.

A Randomized, Double-blind, Placebo-Controlled Crossover Trial of Oxymorphone Hydrochloride and Propoxyphene/Acetaminophen Combination for the Treatment of Neurogenic Claudication Associated With Lumbar Spinal Stenosis.

STUDY DESIGN: Randomized, double-blind, placebo-controlled, single-dose crossover study. OBJECTIVE: To test the analgesic efficacy of oxymorphone hydrochloride (OH) and propoxyphene/acetaminophen (PA) for patients with neurogenic claudication associated with lumbar spinal stenosis. SUMMARY OF BACKGROUND DATA: Although opioids are often prescribed for neurogenic claudication, no randomized controlled studies support their efficacy for this condition. Patients with neurogenic claudication are generally excluded from clinical trials or included with patients who have nonspecific chronic low back pain, yielding a heterogeneous study population with very different pathophysiologies and clinical presentations. METHODS: Participants received a single dose of each of the 3 treatments in random order. Treatments were separated by at least 3-day washout periods. The primary outcome variable was the time to first treadmill walking-induced moderate pain (≥4 out of 10 on a Numeric Rating Scale) (Tfirst) assessed 90 minutes after treatment administration. Secondary outcome measures included patient global assessment of low back pain, Roland-Morris Disability Questionnaire, Modified Brief Pain Inventory-Short Form, Oswestry Disability Index, and Swiss Spinal Stenosis Questionnaire. RESULTS: The study was prematurely terminated because of the removal of PA from the US market. Twenty-four patients were randomized; 21 completed all 3 treatment periods. There were no significant differences among the treatment groups with respect to the median Tfirst (OH-placebo: median [98.3% confidence limits]=-0.25 min [-6.54, 5.00]; PA-placebo: 0.02 min [-7.65, 4.90]; OH-PA: -0.27 min [-5.56, 6.66]). CONCLUSION: This trial failed to demonstrate a benefit of OH or PA in patients experiencing neurogenic claudication. Considering the potential negative side effects of chronic opioid use, additional research is necessary to evaluate the efficacy of sustained opioid treatment specifically for neurogenic claudication. LEVEL OF EVIDENCE: 2.

Double-blind, randomized, controlled, crossover trial of pregabalin for neurogenic claudication.

OBJECTIVES: To test the effects of pregabalin on the induction of neurogenic claudication. METHODS: This study was a randomized, double-blind, active placebo-controlled, 2-period, crossover trial. Twenty-nine subjects were randomized to receive pregabalin followed by active placebo (i.e., diphenhydramine) or active placebo followed by pregabalin. Each treatment period lasted 10 days, including a 2-step titration. Periods were separated by a 10-day washout period, including a 3-day taper phase after the first period. The primary outcome variable was the time to first moderate pain symptom (Numeric Rating Scale score ≥4) during a 15-minute treadmill test (Tfirst). Secondary outcome measures included pain intensity at rest, pain intensity at the end of the treadmill test, distance walked, and validated self-report measures of pain and functional limitation including the Roland-Morris Disability Questionnaire, modified Brief Pain Inventory-Short Form, Oswestry Disability Index, and Swiss Spinal Stenosis Questionnaire. RESULTS: No significant difference was found between pregabalin and active placebo for the time to first moderate pain symptom (difference in median Tfirst = -1.08 [95% confidence interval -2.25 to 0.08], p = 0.61). In addition, none of the secondary outcome measures of pain or functional limitation were significantly improved by pregabalin compared with active placebo. CONCLUSIONS: Pregabalin was not more effective than active placebo in reducing painful symptoms or functional limitations in patients with neurogenic claudication associated with lumbar spinal stenosis. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients with neurogenic claudication, compared with diphenhydramine, pregabalin does not increase the time to moderate pain during a treadmill test.