Pain relief and functional improvement in patients with neuropathic pain associated with spinal cord injury: an exploratory analysis of pregabalin clinical trials.

BACKGROUND: Characterizing relationships between pain relief and function can inform patient management decisions. This analysis explored graphically the relationship between pain relief and functional improvement in patients with neuropathic pain associated with spinal cord injury in two clinical trials of pregabalin. METHODS: This was a post hoc analysis of two randomized, double-blind, clinical trials in patients who were treated with pregabalin (n=181) or placebo (n=172) for neuropathic pain associated with spinal cord injury. The bivariate relationship between percent pain relief and absolute change in the functional outcomes with placebo and pregabalin was evaluated graphically using scatter plots, and loess curves illustrated the extent of the relationship between pain and function. Linear trend analysis evaluated the statistical significance of these relationships using Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT)-based thresholds of pain reduction (<15%, 15% <30%, 30% to <50%, and ≥50%). Outcome measures included modified Brief Pain Inventory pain interference with function in one of the studies and the Medical Outcomes Study Sleep Scale (an 11-point Numeric Rating Scale) and the Hospital Anxiety and Depression Scale (HADS) for the pooled studies. RESULTS: Data ellipses showed a shift with pregabalin relative to placebo toward greater improvement with increasing pain relief for all outcome measures except HADS. Loess curves suggested a relationship between increased pain relief and improved function except for HADS, with the clearest relationship observed for sleep. Linear trend analysis showed significant relationships between pain and Medical Outcomes Study Sleep Scale (P<0.0001) and between pain and function on the modified Brief Pain Inventory Interference Index and most individual items (P<0.05). CONCLUSION: Greater functional improvements were generally achieved at higher levels of clinically significant pain reduction. Pregabalin resulted in shifts from placebo toward greater functional improvement with greater pain relief.

Burden of HIV-Related Neuropathic Pain in the United States.

BACKGROUND: HIV-related neuropathic pain (HIV-NeP) is common; however, the burden of HIV-NeP is not well-understood. METHODS: The cross-sectional study aimed to characterize the HIV-NeP burden. A total of 103 patients with HIV-NeP recruited during routine office visits completed a questionnaire to assess patient-reported outcomes, including pain severity, health status, sleep, mood, and lost productivity. Physicians completed a 6-month retrospective chart review. RESULTS: The sample was predominantly male and not employed for pay. A majority (75.7%) of patients experienced moderate or severe pain. Pain interference, general health, physical health, and depression were worse among patients with more severe pain (all Ps < .006). Most (87.4%) patients were prescribed at least 1 medication for NeP. HIV-related neuropathic pain was associated with 36.1% work impairment. Adjusted annualized costs increased with increasing pain severity (P < .0001). CONCLUSION: The impact of HIV-NeP on health status, physical function, and depression increases with severity, resulting in substantial clinical and economic burden.

Pain severity and the economic burden of neuropathic pain in the United States: BEAT Neuropathic Pain Observational Study.

BACKGROUND: As with many chronic conditions, patients with neuropathic pain (NeP) are high consumers of health care resources. However, limited literature exists on the economic burden of NeP, including its impact on productivity. The aim of this study was to characterize health care resource utilization, productivity, and costs associated with NeP by pain severity level in US adults. METHODS: Subjects (n=624) with painful diabetic peripheral neuropathy, human immunodeficiency virus-related peripheral NeP, post-trauma/post-surgical NeP, spinal cord injury with NeP, chronic low back pain with NeP, and small fiber neuropathy were recruited during routine office visits to US community-based general practitioners and specialists. Clinicians captured clinical characteristics, NeP-related medications, and health care resource utilization based on 6-month retrospective medical chart review. Subjects completed questionnaires on demographics, pain/symptoms, costs, and productivity. Brief Pain Inventory pain severity scores were used to classify subjects by mild, moderate, or severe pain. Annualized NeP-related costs (adjusted for covariates) were estimated, and differences across pain severity groups were evaluated. RESULTS: In total, 624 subjects were recruited (mean age 55.5±13.7 years; 55.4% male), and 504/624 (80.8%) reported moderate or severe pain. Statistically significant differences were observed across pain severity levels for number of comorbidities, prescription medications, physician office visits, and lost productivity (all P≤0.0001). At all pain severity levels, indirect costs were the primary cost driver. After adjusting for demographic and clinical variables, total mean (95% confidence interval [CI]) annualized direct medical costs to payers, direct costs to subjects, and indirect costs per subject were US$6,016 (95% CI 5,316-6,716), US$2,219 (95% CI 1,919-2,519), and US$19,000 (95% CI 17,197-20,802), respectively, with significant differences across pain severity levels. CONCLUSION: Subjects with NeP, mainly those showing moderate or severe pain, had significant associations between pain severity and NeP-related health care resource utilization, productivity, and costs. The economic burden, particularly indirect costs, was highest among those with severe pain and higher than previously reported in studies of specific NeP conditions.

Health care resource utilization and medical costs of spinal cord injury with neuropathic pain in a commercially insured population in the United States.

OBJECTIVE: To evaluate health care resource use, costs, and cost drivers among patients with neuropathic pain (NeP) after spinal cord injury (SCI) in a commercially insured population. DESIGN: Retrospective longitudinal cohort study comparing SCI patients with and without NeP. SETTING: Truven Health MarketScan commercial claims database from 2005 through 2012. PARTICIPANTS: Commercially insured SCI patients with NeP (n=3524) propensity score matched to SCI patients without NeP (n=3524). INTERVENTIONS: Not applicable. MAIN OUTCOMES MEASURES: Health care resource utilization and expenditures for the 12 months after NeP onset (index event; identified through International Classification of Diseases, 9th Revision, Clinical Modification diagnosis 338.0x or use of NeP-specific antiepileptic drugs or NeP-specific antidepressants) in patients with SCI compared with matched patients without NeP. RESULTS: Utilization over 12 months postindex among patients with SCI-associated NeP was higher than among SCI-only patients for inpatient admissions (27.4% vs 22.1%), emergency department visits (36.7% vs 26.4%), and office visits per patient (mean ± SD: 13.0±9.5 vs 9.5±8.3); all P values were <.001. All-cause expenditures showed adjusted incremental costs of $22,545 (95% confidence interval, $19,010-$26,168) per patient with SCI-associated NeP during the 12-month postindex period. CONCLUSIONS: Patients with evidence of NeP secondary to SCI have significantly higher health care utilization and total costs compared with SCI patients without evidence of NeP. Factors contributing to NeP in patients with SCI need to be clinically assessed to determine the optimal approach for treating these individuals.

Health care utilization and expenditures among Medicaid beneficiaries with neuropathic pain following spinal cord injury.

BACKGROUND: The study aimed to evaluate health care resource utilization (HRU) and costs for neuropathic pain (NeP) secondary to spinal cord injury (SCI) among Medicaid beneficiaries. METHODS: The retrospective longitudinal cohort study used Medicaid beneficiary claims with SCI and evidence of NeP (SCI-NeP cohort) matched with a cohort without NeP (SCI-only cohort). Patients had continuous Medicaid eligibility 6 months pre- and 12 months postindex, defined by either a diagnosis of central NeP (ICD-9-CM code 338.0x) or a pharmacy claim for an NeP-related antiepileptic or antidepressant drug within 12 months following first SCI diagnosis. Demographics, clinical characteristics, HRU, and expenditures were compared between cohorts. RESULTS: Propensity score-matched cohorts each consisted of 546 patients. Postindex percentages of patients with physician office visits, emergency department visits, SCI- and pain-related procedures, and outpatient prescription utilization were all significantly higher for SCI-NeP (P<0.001). Using regression models to account for covariates, adjusted mean expenditures were US$47,518 for SCI-NeP and US$30,150 for SCI only, yielding incremental costs of US$17,369 (95% confidence interval US$9,753 to US$26,555) for SCI-NeP. Factors significantly associated with increased cost included SCI type, trauma-related SCI, and comorbidity burden. CONCLUSION: Significantly higher HRU and total costs were incurred by Medicaid patients with NeP secondary to SCI compared with matched SCI-only patients.

Burden of illness associated with peripheral and central neuropathic pain among adults seeking treatment in the United States: a patient-centered evaluation.

OBJECTIVE: The aim of this study was to evaluate patient-reported burden associated with peripheral and central neuropathic pain (NeP) by pain severity and NeP condition. DESIGN: Six hundred twenty-four subjects with one of six NeP conditions were recruited during routine office visits. Subjects consented to retrospective chart review and completed a one-time questionnaire (including EuroQol-5 dimensions, 12-item Short-Form Health Survey, Brief Pain Inventory-Short Form, Medical Outcomes Study Sleep Scale, Hospital Anxiety and Depression Scale, and demographic and clinical characteristics). Pain severity scores were used to stratify subjects by mild, moderate, and severe pain. Summary statistics and frequency distributions were calculated. Differences by severity level were compared using Kruskal-Wallis (continuous variables) and chi-square or Fisher's exact test (categorical variables). Effect size was computed with Cohen's d (mild vs severe). RESULTS: Subjects' mean age was 55.5. The majority (80.8%) had moderate or severe pain. Patient-reported outcomes (health status, physical and mental health, pain interference with function, sleep, anxiety, and depression) were significantly worse among subjects with greater pain severity (all P < 0.0001). Severe pain subjects were negatively impacted by ≥30% in each outcome compared with mild pain subjects; standardized effect size was moderate for anxiety (0.59) and large (>0.95) for all others. The observed burden was most substantial among chronic low back pain-NeP, although the pattern of disease burden was similar across the six NeP conditions. CONCLUSIONS: Subjects across NeP conditions exhibited high pain levels, which were significantly associated with poor function, compromised health status and sleep, and increased anxiety and depression. Results indicate substantial patient burden across broad NeP, particularly among subjects with severe pain.

Health status, function, productivity, and costs among individuals with idiopathic painful peripheral neuropathy with small fiber involvement in the United States: results from a retrospective chart review and cross-sectional survey.

OBJECTIVE: To characterize the burden of idiopathic painful peripheral neuropathy with small fiber involvement (idiopathic SFN) by pain severity in the US. METHODS: One hundred previously diagnosed idiopathic SFN subjects were enrolled during routine office visits. Subjects completed a one-time questionnaire, and investigators reported clinical characteristics and healthcare resource use, based on 6 month retrospective chart review. Annualized direct and indirect costs were estimated. Results were stratified across pain severity groups. RESULTS: Mean age was 63.5 years; 53.0% were female; 76.0% had moderate or severe pain. Most common comorbidities were sleep disturbance/insomnia (37.0%), anxiety (34.0%), and depressive symptoms (33.0%). Overall mean health status (0.59; -0.11-1.00 scale), physical and mental health (31.7 and 45.6, respectively, 0-100 scale), sleep index (45.1; 0-100 scale), and pain interference with function (5.0; 0-10 scale) differed by pain severity, with worse outcomes among those with greater pain (all p < 0.002). 84.0% were prescribed ≥1 SFN medication. 16.0% were employed; mean overall work impairment was 36.9%. Annualized average adjusted direct and indirect costs per subject ($8055 and $13,733, respectively) differed by pain severity. CONCLUSIONS: Idiopathic SFN subjects with pain experience moderate or severe pain, which negatively impacts health status, function, and productivity, and leads to substantial direct and indirect costs.

Economic and humanistic burden of post-trauma and post-surgical neuropathic pain among adults in the United States.

BACKGROUND: Neuropathic pain (NeP) can be chronic, debilitating, and can interfere with sleep, functioning, and emotional well being. While there are multiple causes of NeP, few studies have examined the disease burden and treatment patterns associated with post-traumatic/post-surgical (PTPS) NeP. OBJECTIVE: To characterize pain, health status, function, health care resource utilization, lost productivity, and costs among subjects with PTPS NeP in the United States. METHODS: This observational study enrolled 100 PTPS NeP subjects recruited during routine visits from general practitioner and specialist sites. Subjects completed a one-time questionnaire with validated measures of pain severity and pain interference, health status, sleep, anxiety and depression, productivity, and study-specific items on demographics, employment status, and out-of-pocket expenses. Investigators completed a case report form based on a 6-month retrospective chart review, recording subjects' clinical characteristics as well as current and previous medications/treatments for NeP. Subjects were stratified into mild, moderate, and severe pain groups. RESULTS: Subjects' demographic characteristics were: mean age of 54.9 years, 53% female, and 22% employed for pay. Mean pain severity score was 5.6 (0-10 scale), with 48% and 35% classified as having moderate and severe pain, respectively. The mean number of comorbidities increased with greater pain severity (P = 0.0009). Patient-reported outcomes were worse among PTPS NeP subjects with more severe pain, including pain interference with function, health state utility, sleep, and depression (P < 0.0001). Eighty-two percent of subjects were prescribed two or more NeP medications. The total mean annualized adjusted direct and indirect costs per subject were $11,846 and $29,617, respectively. Across pain severity levels, differences in annualized adjusted direct and indirect costs were significant (P < 0.0001). CONCLUSION: PTPS NeP subjects reported high pain scores, which were associated with poor health utility, sleep, mood, and function, as well as high health care resource utilization and costs. The quality of life impact and costs attributable to PTPS NeP suggest an unmet need for effective and comprehensive management.

Burden of illness associated with painful diabetic peripheral neuropathy among adults seeking treatment in the US: results from a retrospective chart review and cross-sectional survey.

BACKGROUND: The purpose of this study was to characterize the burden of illness among adult subjects with painful diabetic peripheral neuropathy (pDPN) seeking treatment in the US. METHODS: This observational study recruited 112 subjects with pDPN during routine visits from general practitioner and specialist sites. Subjects completed a one-time questionnaire, which included demographics, symptom duration, health care resource use, out-of-pocket costs, employment status, and validated measures that assessed pain, functioning, sleep, anxiety and depression, health status, and productivity. Investigators completed a case report form based on a 6-month retrospective chart review to capture clinical information, pDPN-related treatments, and other pDPN-related health care resource use over the past 6 months. Annualized costs were extrapolated based on reported 6-month health care resource use. RESULTS: The mean age of the subjects was 61.1 years, 52.7% were female, and 17.9% were in paid employment. The most common comorbid conditions were sleep disturbance/insomnia (43.8%), depressive symptoms (41.1%), and anxiety (35.7%). The mean pain severity score was 5.2 (0-10 scale), and 79.5% reported moderate or severe pain. The mean pain interference with function score was 5.0 (0-10 scale) overall, with 2.0 among mild, 5.1 among moderate, and 7.0 among severe. The mean Medical Outcomes Study sleep problems index score was 48.5 (0-100 scale). The mean health state utility score was 0.61. Among subjects employed for pay, mean overall work impairment was 43.6%. Across all subjects, mean overall activity impairment was 52.3%. In total, 81.3% were prescribed at least one medication for their pDPN; 50.9% reported taking at least one nonprescription medication. Adjusted mean annualized total direct and indirect costs per subject were $4841 and $9730, respectively. Outcomes related to pain interference with function, sleep, health status, activity impairment, prescription medication use, and direct and indirect costs were significantly worse among subjects with more severe pain (P < 0.0020). CONCLUSION: Subjects with pDPN exhibited high pain levels, which were associated with poor sleep, function, and productivity. Health care resource utilization in pDPN was prevalent and costs increased with greater pain severity. The burden of pDPN was greater among subjects with greater pain severity.

A randomized trial of pregabalin in patients with neuropathic pain due to spinal cord injury.

OBJECTIVE: To assess the efficacy and tolerability of pregabalin for the treatment of central neuropathic pain after spinal cord injury (SCI). METHODS: Patients with chronic, below-level, neuropathic pain due to SCI were randomized to receive 150 to 600 mg/d pregabalin (n = 108) or matching placebo (n = 112) for 17 weeks. Pain was classified in relation to the neurologic level of injury, defined as the most caudal spinal cord segment with normal sensory and motor function, as above, at, or below level. The primary outcome measure was duration-adjusted average change in pain. Key secondary outcome measures included the change in mean pain score from baseline to end point, the percentage of patients with ≥30% reduction in mean pain score at end point, patient global impression of change scores at end point, and the change in mean pain-related sleep interference score from baseline to end point. Additional outcome measures included the medical outcomes study-sleep scale and the Hospital anxiety and depression scale. RESULTS: Pregabalin treatment resulted in statistically significant improvements over placebo for all primary and key secondary outcome measures. Significant pain improvement was evident as early as week 1 and was sustained throughout the treatment period. Adverse events were consistent with the known safety profile of pregabalin and were mostly mild to moderate in severity. Somnolence and dizziness were most frequently reported. CONCLUSIONS: This study demonstrates that pregabalin is effective and well tolerated in patients with neuropathic pain due to SCI. CLASSIFICATION OF EVIDENCE: This study provides class I evidence that pregabalin, 150 to 600 mg/d, is effective in reducing duration-adjusted average change in pain compared with baseline in patients with SCI over a 16-week period (p = 0.003, 95% confidence interval = -0.98, -0.20).

Double-blinded, placebo-controlled trial of midodrine for exercise performance enhancement in tetraplegia: a pilot study.

BACKGROUND/OBJECTIVE: Spinal cord injury (SCI) impairs cardiovascular autonomic responses to exercise and, depending on the level of injury, may result in hypotension and pathologic fatigue with exertion. Other clinical populations with sympathetic regulatory dysfunction, but without skeletal muscle paralysis, exhibit similar signs and symptoms. Their ability to engage in physical activity improves with elevation of blood pressure through pharmacologic treatment: Midodrine, an oral alpha-sympathomimetic agent, has been shown to be safe and efficacious for this purpose. Use of this medication in individuals with SCI merits investigation. METHODS: Double-blind, placebo-controlled, randomized, crossover, within-subjects protocol. Four participants with chronic, motor-complete injuries from C6 to C8 underwent 4 peak exercise tests (PXT) using a wheelchair ergometer, following administration of midodrine, 5 mg, 10 mg, and placebo, in random order. Heart rate, blood pressure, oxygen consumption (VO2), and perceived exertion were measured. RESULTS: Treatment with midodrine, 10 mg, was associated with elevated systolic blood pressure during peak exercise in 3 participants. Two participants showed a concurrent decrease in perceived exertion and increase in VO2. No adverse effects of midodrine were evident. CONCLUSION: Midodrine enhances exercise performance in some individuals with SCI, similar to other clinical populations with cardiovascular autonomic dysfunction.