The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Multicenter Study
A randomized, double-blind, placebo-controlled trial to assess the efficacy and safety of gabapentin enacarbil in subjects with neuropathic pain associated with postherpetic neuralgia (PXN110748).
Gabapentin enacarbil (GEn) is an actively transported prodrug of gabapentin that provides sustained, dose-proportional exposure to gabapentin. This randomized, double-blind, parallel-group, placebo-controlled study evaluated the safety and efficacy of 3 different maintenance doses of oral GEn in subjects with postherpetic neuralgia. Adults with a 24-hour average pain intensity score of ≥4.0 received GEn 1,200 mg, 2,400 mg, 3,600 mg, or placebo for 14 weeks (including a 1-week up-titration, 12-week maintenance, and 1-week taper). The primary endpoint was change from baseline to end of maintenance treatment in mean 24-hour average pain intensity score. The intent-to-treat population consisted of 371 subjects (GEn 1,200 mg = 107, 2,400 mg = 82, 3,600 mg = 87, placebo = 95). With regard to the primary endpoint, all 3 GEn treatment groups demonstrated a statistically significant difference relative to placebo. The adjusted mean change from baseline for the treatment groups ranged from -2.36 to -2.72 versus -1.66 for the placebo group. Exposure-response modeling suggested an ED50 around 1,200 mg/day, which was consistent with historical findings reported for gabapentin. The most commonly reported adverse events were dizziness and somnolence. All studied doses of GEn significantly improved pain associated with postherpetic neuralgia as compared to placebo and were well tolerated. ⋯ GEn provides clinically important pain relief with doses from 1,200 mg to 3,600 mg and is generally well tolerated and efficacious. As an actively transported prodrug of gabapentin, it provides dose-proportional and extended exposure to gabapentin.
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Randomized Controlled Trial Multicenter Study
A randomized, placebo-controlled study of the impact of the 7-day buprenorphine transdermal system on health-related quality of life in opioid-naïve patients with moderate-to-severe chronic low back pain.
This study evaluated the impact of treatment with Buprenorphine Transdermal System (BTDS) on the health-related quality of life for patients with moderate-to-severe chronic low back pain (CLBP), and the correspondence between quality of life and pain. A multicenter, enriched, double-blind (DB), placebo-controlled, randomized trial evaluated BTDS 10 and 20 μg/hour for treatment of opioid-naïve patients with moderate-to-severe CLBP. The SF-36v2 survey, which measures 8 domains of quality of life, was administered at screening and following an open-label run-in period with BTDS and at weeks 4, 8, and 12 of the DB phase. Post hoc analyses compared SF-36v2 scores between BTDS and placebo groups during the DB phase. Condition burden was examined through comparisons with a U.S. general population sample. Correlations examined the correspondence between quality of life and pain measures. BTDS produced larger improvements than placebo at 12 weeks in all quality-of-life domains (Ps < .05). Treatment group differences in both physical and mental quality of life emerged by 4 weeks. Patients' pretreatment quality of life was worse than that in the general population (Ps < .05); only BTDS treatment eliminated deficits in pain, social functioning, and role limitations due to emotional health. Improvements in quality of life were moderately associated with pain reduction. These data suggest that moderate-to-severe CLBP patients receiving BTDS exhibited better quality of life than patients receiving placebo. ⋯ This post hoc analysis suggests that patients with moderate-to-severe CLBP treated with BTDS exhibit better health-related quality of life than those using placebo within 4 weeks of treatment, and were more likely to exhibit clinically meaningful improvements in quality of life following 12 weeks of treatment.
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Randomized Controlled Trial Multicenter Study
Viscerosomatic facilitation in a subset of IBS patients, an effect mediated by N-methyl-D-aspartate receptors.
Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which the pathophysiological mechanisms of the pain and hypersensitivity are incompletely understood. IBS patients frequently complain of pain in body regions somatotopically distinct from the gut, suggesting involvement of central hyperalgesic mechanisms. We tested the role of tonic peripheral impulse input by using both repetitive thermal stimuli to the leg and repetitive stimuli to the rectum. Changes in thermal/visceral pain sensitivity after nociceptive thermal/visceral repetitive stimulation were determined. A subset of IBS patients showed enhanced rectal/thermal pain sensitivity after repetitive thermal/rectal stimulation, respectively. IBS patients then received 60 mg dextromethorphan and placebo (diphenhydramine) in a randomized, double-blind, crossover trial. The results showed that 1) a subset of IBS patients had increased visceral/cutaneous hypersensitivity following a series of repetitive nociceptive stimuli and that 2) this increased pain sensitivity was blocked by administration of dextromethorphan. This is the first human study indicating that repetitive stimulation enhances a bidirectional mechanism of secondary hyperalgesia due to viscerosomatic facilitation in IBS patients. These unique findings elucidate mechanisms of somatic hypersensitivity in IBS patients and support an etiologic basis for abnormal N-methyl-D-aspartate receptor mechanisms that may be the target of future therapies for IBS. ⋯ Repetitive stimulation enhances a bidirectional mechanism of secondary hyperalgesia due to viscerosomatic convergence in IBS patients. The findings elucidate unique mechanisms of somatic/visceral hypersensitivity in a subset of IBS patients and further support an etiologic basis for abnormal N-methyl-D-aspartate receptor mechanisms that may be future targets of therapies for IBS.
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Multicenter Study
Pain assessment and intensity in hospitalized children in Canada.
Numerous acute pediatric pain assessment measures exist; however, pain assessment is not consistently performed in hospitalized children. The objective of this study was to determine the nature and frequency of acute pain assessment in Canadian pediatric hospitals and factors influencing it. Pain assessment practices and pain intensity scores documented during a 24-hour period were collected from 3,822 children aged 0 to 18 years hospitalized on 32 inpatient units in 8 Canadian pediatric hospitals. Pain assessment was documented at least once within the 24 hours for 2,615/3,822 (68.4%) children; 1,097 (28.7%) with a pain measure alone, 1,006 (26.3%) using pain narratives alone, and 512 (13.4%) with both a measure and narrative. Twenty-eight percent of assessments were conducted with validated measures. The mean standardized pain intensity score was 2.6/10 (SD 2.8); however, 33% of the children had either moderate (4-6/10) or severe (7-10/10) pain intensity recorded. Children who were older, ventilated, or hospitalized in surgical units were more likely to have a pain assessment score documented. Considerable variability in the nature and frequency of documented pain assessment in Canadian pediatric hospitals was found. These inconsistent practices and significant pain intensity in one-third of children warrant further research and practice change. ⋯ This article presents current pediatric pain assessment practices and data on pain intensity in children in Canadian pediatric hospitals. These results highlight the variability in pain assessment practices and the prevalence of significant pain in hospitalized children, highlighting the need to effectively manage pain in this population.
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Randomized Controlled Trial Multicenter Study Comparative Study
Comparative responsiveness of pain measures in cancer patients.
Brief measures to assess and monitor pain in cancer patients are available, but few head-to-head psychometric comparisons of different measures have been reported. Baseline and 3-month data were analyzed from 274 patients enrolled in the Indiana Cancer Pain and Depression (INCPAD) trial. Participants completed the Brief Pain Inventory (BPI), the PEG (a 3-item abbreviated version of the BPI), the short form (SF)-36 pain scale, and a pain global rating of change measure. The global rating was used as the criterion for standardized response mean and receiver operating characteristic curve analyses. To assess responsiveness to the trial intervention, we evaluated standardized effect size statistics stratified by trial arm. All measures were responsive to global improvement, discriminated between participants with and without improvement, and detected a significant intervention treatment effect. Short and longer measures were similarly responsive. Also, composite measures that combined pain severity and interference into a single score (BPI total, PEG, SF-36 pain) performed comparably to separate measures of each domain (BPI severity and BPI interference). ⋯ Pain measures as brief as 2 or 3 items that provide a single score are responsive in patients with cancer-related pain. Ultra-brief measures offer a valid and efficient means of assessing and monitoring pain for the clinical management as well as research of cancer-related pain.