Pregabalin in central neuropathic pain associated with spinal cord injury: A placebo-controlled trial

Prediction of therapeutic response to pregabalin in subjects with neuropathic pain

OBJECTIVE

To evaluate four models based on potential predictors for achieving a response to pregabalin treatment for neuropathic pain (NeP).

METHODS

In total, 46 pain studies were screened, of which 27 NeP studies met the criteria for inclusion in this analysis. Data were pooled from these 27 placebo-controlled randomized trials to assess if baseline characteristics (including mean pain and pain-related sleep interference [PRSI] scores), early clinical response during weeks 1-3 of treatment (change from baseline in pain and PRSI scores), and presence of treatment-emergent adverse events (AEs) were predictive of therapeutic response. Therapeutic response was defined as a ≥30% reduction from baseline in either pain and/or PRSI scores at week 5 with supplemental analyses to predict pain outcomes at weeks 8 and 12. Predictors of Patient Global Impression of Change (PGIC) were also evaluated. Four models were assessed: Random Forest, Logistic Regression, Naïve Bayes, and Partial Least Squares.

RESULTS

The number of pregabalin-treated subjects in the training/test datasets, respectively, were 2818/1407 (30% pain analysis), 2812/1405 (30% sleep analysis), and 2693/1345 (PGIC analysis). All four models demonstrated consistent results, and the most important predictors of treatment outcomes at week 5 and pain outcomes at weeks 8 and 12 were the reduction in pain score and sleep score in the first 1-3 weeks. The presence or absence of the most common AEs in the first 1-3 weeks was not correlated with any treatment outcome.

CONCLUSIONS

Subjects with an early response to pregabalin are more likely to experience an end-of-treatment response.

Pain Management in Athletes With Impairment: A Narrative Review of Management Strategies

OBJECTIVE

To review the literature related to different treatment strategies for the general population of individuals with amputation, spinal cord injury, and cerebral palsy, as well as how this may impact pain management in a correlated athlete population.

DATA SOURCES

A comprehensive literature search was performed linking pain with terms related to different impairment types.

MAIN RESULTS

There is a paucity in the literature relating to treatment of pain in athletes with impairment; however, it is possible that the treatment strategies used in the general population of individuals with impairment may be translated to the athlete population. There are a wide variety of treatment options including both pharmacological and nonpharmacological treatments which may be applicable in the athlete.

CONCLUSIONS

It is the role of the physician to determine which strategy of the possible treatment options will best facilitate the management of pain in the individual athlete in a sport-specific setting.

Long-Term Outcomes in the Management of Central Neuropathic Pain Syndromes: A Prospective Observational Cohort Study

Background:Central neuropathic pain syndromes are a result of central nervous system injury, most commonly related to stroke, traumatic spinal cord injury, or multiple sclerosis. These syndromes are distinctly less common than peripheral neuropathic pain, and less is known regarding the underlying pathophysiology, appropriate pharmacotherapy, and long-term outcomes. The objective of this study was to determine the long-term clinical effectiveness of the management of central neuropathic pain relative to peripheral neuropathic pain at tertiary pain centers.Methods:Patients diagnosed with central (n=79) and peripheral (n=710) neuropathic pain were identified for analysis from a prospective observational cohort study of patients with chronic neuropathic pain recruited from seven Canadian tertiary pain centers. Data regarding patient characteristics, analgesic use, and patient-reported outcomes were collected at baseline and 12-month follow-up. The primary outcome measure was the composite of a reduction in average pain intensity and pain interference. Secondary outcome measures included assessments of function, mood, quality of life, catastrophizing, and patient satisfaction.Results:At 12-month follow-up, 13.5% (95% confidence interval [CI], 5.6-25.8) of patients with central neuropathic pain and complete data sets (n=52) achieved a ≥30% reduction in pain, whereas 38.5% (95% CI, 25.3-53.0) achieved a reduction of at least 1 point on the Pain Interference Scale. The proportion of patients with central neuropathic pain achieving both these measures, and thus the primary outcome, was 9.6% (95% CI, 3.2-21.0). Patients with peripheral neuropathic pain and complete data sets (n=463) were more likely to achieve this primary outcome at 12 months (25.3% of patients; 95% CI, 21.4-29.5) (p=0.012).Conclusion:Patients with central neuropathic pain syndromes managed in tertiary care centers were less likely to achieve a meaningful improvement in pain and function compared with patients with peripheral neuropathic pain at 12-month follow-up.

The analgesic effect of intravenous methylprednisolone on acute neuropathic pain with allodynia due to central cord syndrome: a retrospective study

Background

Central cord syndrome (CCS) may be associated with severe neuropathic pain that often resists to conventional pain therapy regimens and affects the patients’ quality of life (QoL) seriously. Current treatments for CCS-associated neuropathic pain have limited evidence of efficacy. This retrospective study was performed to present the effects of early treatment with methylprednisolone (MP) on acute neuropathic pain relief and the QoL in CCS patients.

Patients and methods

Data were collected from the medical records of CCS patients who suffered from acute neuropathic pain with allodynia. All the patients received intravenous MP treatment for up to 1 week. Patients were evaluated with standard measures of efficacy: neuropathic pain intensity, the area of allodynia, and the QoL at baseline, daily treatment, and at 1 and 3 months after the end of MP treatment.

Results

Thirty-four eligible patients were enrolled in our study. By the end of MP treatment, the proportion of patients who gained total or major (visual analog scale [VAS] score decreased by 50% or more) allodynia relief from the treatment was 91.18%, and a decrease in spontaneous pain was also observed. Moreover, this study showed MP could significantly improve the QoL of patients based on McGill Pain Questionnaire Short Form and EuroQol Five Dimensions Questionnaire. Four patients (11.76%) during MP treatment experienced mild or moderate side effects. None of the patients manifested CCS-associated neuropathic pain recurrence and MP-associated side effects at follow-up.

Conclusion

The current results suggested that MP offered an effective therapeutic alternative for relieving CCS-associated acute neuropathic pain with allodynia. Given the encouraging results of this study, it would be worthwhile to confirm these results in randomized placebo-controlled clinical trials.

Placebo response in neuropathic pain after spinal cord injury: a meta-analysis of individual participant data

Background

Understanding factors associated with high placebo responses in clinical trials increases the likelihood of detecting a meaningful treatment effect. The aim of the present study was to identify subject-level factors that contribute to placebo variability in patients with neuropathic pain due to spinal cord injury (SCI).

Methods

Multiple regression analysis of patient data from randomized, double-blind, placebo-controlled trials (duration >4 weeks) involving individuals with SCI was performed. Patient demographics, as well as injury and pain characteristics were examined for their association with changes in pain rating from baseline to the end of the trial (i.e., placebo response). The overall effect of individual predictors was quantified with meta-analysis statistics.

Results

A total of 276 patients with SCI from six studies were included in the analysis. Based on the meta-analysis of subject-level predictors, larger placebo responses were associated with male subjects (β=0.635; standard error [SE]=0.262; p=0.016) and higher baseline pain (β=−0.146; SE=0.073; p=0.044). There were no significant effects for injury characteristics (i.e., severity, level, and time since injury) or pain characteristics (i.e., location and evoked). No significant publication bias was detected.

Conclusion

The current meta-analysis of individual patient data demonstrated the importance of sex and baseline pain intensity on changes in pain ratings in the placebo arm of SCI central neuropathic pain randomized controlled clinical trials. Overall, our findings indicate that placebo responses occur independent of injury characteristics.

The Effect of Pregabalin and Metformin on Subacute and Chronic Radiculopathy

Background:

Radicular pain is one of the most common forms of chronic pain in the world, which has challenges about effective medical therapy. The aim of this study was to evaluate the effect of pregabalin (PGB) and metformin (Met) on subacute and chronic radiculopathy.

Materials and Methods:

This double-blind prospective clinical trial was performed on 71 patients with subacute and chronic cervical and lumbosacral radiculopathy. Group A was treated with PGB 75 mg daily while Group B was treated with PGB 75 mg daily and Met 500 mg daily for 3 months. Finally, the pain score in both groups was evaluated based on visual analog scale (VAS) and numerical scale pain.

Results:

The results showed a significant reduction in VAS and pain severity in both groups but this reduction in the terms of VAS (47.79% vs. 46.48%, P = 0.125) and pain severity (47.1% vs. 39.2%, P = 0.264) was more in treated patients with PGB and Met as compared to PGB group while total pain experience (53.5% vs. 49.1%, P = 0.464) and interference with daily function (57.1% vs. 50.61%, P = 0.726) were more in patients treated with PGB alone.

Conclusion:

Our results showed that PGB and PGB + Met reduced pain intensity and interference with daily function while we did not observe significant differences between two groups. PGB alone would have the potentiality to become a simple and economic means to decrease radicular pain.

TRPA1 polymorphisms in chronic and complete spinal cord injury patients with neuropathic pain: a pilot study

Study design

Pilot study.

Objectives

Single-nucleotide polymorphisms (SNPs) in TRPA1 gene are related to the etiology of chronic pain. The study is a pilot study with the primary objective of analyzing these SNPs in Spanish patients with chronic and complete spinal cord injury (SCI) and neuropathic pain (NPP).

Setting

Asepeyo Hospital Department of Chronic and Complete SCI.

Methods

Twelve patients with chronic and complete SCI and NPP, and 12 patients with chronic and complete SCI with no pain were reviewed. International Spinal Cord Injury Pain Classification (LANSS) and visual analog score (VAS) were chosen to classify pain syndrome. SNPs were identified by melting analysis after DNA amplification with real-time fluorescence PCR.

Results

There were differences in rs11988795 variant: GG homozygous (p = 0.01) and G allele (p = 0.001) were more frequent in SCI patients with no pain. There were differences in rs13255063 variant: TT homozygous were prevalent (p = 0.03) in patients with NPP.

Conclusions

Until now this is the first study to show a description of TRPA1 SNPs in Spanish patients with chronic and complete SCI and NPP. These results suggest that GG genotype in rs11988795 variant and G allele could be protective factors against NPP. TT genotype in rs13255063 variant could be a risk factor for NPP. Neuropathic pain after spinal cord injuries may have genetic contributions.

Pregabalin versus placebo in targeting pro-nociceptive mechanisms to prevent chronic pain after whiplash injury in at-risk individuals - a feasibility study for a randomised controlled trial

BACKGROUND

Whiplash-associated disorders (WAD) are an enormous and costly burden to Australian society. Up to 50% of people who experience a whiplash injury will never fully recover. Whiplash is resistant to treatment and no early management approach has yet been shown to prevent chronic pain. The early presence of central sensitization is associated with poor recovery. Pregabalin's effects on central sensitization indicate the potential to prevent or modulate these processes after whiplash injury and to improve health outcomes, but this has not been investigated. This paper describes the protocol for a feasibility study for a randomised controlled trial of pregabalin plus evidence-based advice compared to placebo plus evidence-based advice for individuals with acute whiplash injury who are at risk of poor recovery.

METHODS

This double blind, placebo-controlled randomised feasibility study will examine the feasibility and potential effectiveness of pregabalin and evidence-based advice (intervention) compared to placebo and evidence-based advice (control) for individuals with acute whiplash injury at risk of poor recovery. Thirty participants (15 per group) aged 18-65 years with Grade II WAD, within 48 hours of injury and currently experiencing at least moderate pain (NRS: ≥ 5/10) will be recruited from Emergency Departments of public hospitals in Queensland, Australia. Pregabalin will be commenced at 75 mg bd and titrated up to 300 mg bd as tolerated for 4 weeks followed by 1 week of weaning.

RESULTS

The feasibility of trial procedures will be tested, as well as the potential effect of the intervention on the outcomes. The primary outcome of neck pain intensity at 3 months from randomisation will be compared between the treatment groups using standard analysis of variance techniques.

DISCUSSION

Feasibility and potential effectiveness data will inform an appropriately powered full trial, which if successful, will provide an effective and cost-effective intervention for a costly and treatment resistant condition. It will also have implications for the early management of other traumatic conditions beyond whiplash.

TRIAL REGISTRATION

Clinical Trials Primary Registry: Australian and New Zealand Clinical Trials Registry.

CLINICAL TRIAL REGISTRATION NUMBER

ACTRN12617000059369 . Date of Registration: 11/01/2017. Primary Trial Sponsor: The University of Queensland, Brisbane QLD 4072 Australia.

Characteristics of Ocular Pain Complaints in Patients With Idiopathic Dry Eye Symptoms

OBJECTIVE

The purpose of this study was to examine the severity and quality of ocular pain complaints in patients with dry eye symptoms.

METHODS

Subjects with clinically relevant dry eye symptoms (dryness, discomfort, tearing) of unknown origin seen in the Miami Veterans Affairs eye clinic were administered questionnaires for dry eye symptoms and ocular pain and underwent a standardized ocular examination. Qualities and severity ratings of ocular pain in subjects with idiopathic dry eye were compared with similar measures from published data in other chronic pain populations.

RESULTS

The study sample consisted of 154 subjects, of which 91% were men and ranged in age from 27 to 89 (mean age=61). Fifty-three percent of participants reported an average ocular pain of at least moderate intensity (numerical rating scale≥4), with specific characteristics (i.e., "burning" spontaneous pain) reported at frequencies comparable to prevalent chronic neuropathic pain syndromes as reported in the literature. Significant correlations were found between ocular pain metrics and dry eye symptom severity scores (r=0.57-0.66). Dry eye signs, however, did not generally correlate with ocular pain severity.

CONCLUSIONS

A significant proportion of subjects with idiopathic dry eye symptoms reported moderate or greater ocular pain intensity, with most endorsing descriptors commonly used by patients with nonocular neuropathic pain conditions. Identifying subgroups of dry eye patients based on the presence and characteristics of ocular pain complaints may improve dry eye subclassification and better individualize treatment strategies.

Dronabinol Is a Safe Long-Term Treatment Option for Neuropathic Pain Patients

Treatment of neuropathic pain (NP) symptoms associated with multiple sclerosis (MS) is frequently insufficient. Yet, cannabis is still rarely offered for treatment of pain. This clinical trial aimed at showing the positive benefit-risk ratio of dronabinol. Two hundred forty MS patients with central NP entered a 16-weeks placebo-controlled phase-III study followed by a 32-weeks open-label period. One hundred patients continued therapy for overall up to 119 weeks. Primary endpoint was change of pain intensity on the 11-point Numerical Rating Scale over a 16-weeks treatment period. Safety was assessed on the basis of adverse reactions (ARs), signs of dependency and abuse. Pain intensity during 16-weeks dronabinol and placebo treatment was reduced by 1.92 and 1.81 points without significant difference in between (p = 0.676). Although the proportion of patients with ARs was higher under dronabinol compared to placebo (50.0 vs. 25.9%), it decreased during long-term use of dronabinol (26%). No signs of drug abuse and only one possible case of dependency occurred. The trial results demonstrate that dronabinol is a safe long-term treatment option.

Pregabalin for the treatment of neuropathic pain: a narrative review for primary care providers

BACKGROUND

Neuropathic pain (NeP) is a distinct type of pain caused by damage to the nervous system itself. This often severe and chronic type of pain requires specific treatments that target the underlying pain pathophysiology.

AIM

The purpose of the current narrative review is to provide an overview of pregabalin (Lyrica ¹ ) for the treatment of NeP including its effects on pain, pain-related sleep interference, and other health-related outcomes, timing of therapeutic effect, safety and tolerability, and dosing. The information provided here will help primary care providers develop more effective NeP treatment strategies.

Neuropathic pain responds better to increased doses of pregabalin: an in-depth analysis of flexible-dose clinical trials

Background

Pregabalin is an effective treatment option for many patients with neuropathic pain. Higher doses of pregabalin have been shown to be more effective in improving pain outcomes but, in practice, failing to appropriately increase the dose can leave patients under-treated.

Methods

This was a pooled analysis of 6 flexible-dose clinical trials of pregabalin in patients with neuropathic pain (diabetic peripheral neuropathy, peripheral herpetic neuralgia, posttraumatic pain, or postsurgical pain). Patients were divided into “dose pathway” groups based on their weekly pregabalin dose from the start of their trial to the first week of their maintenance phase. These were: 150 mg/day only; 150 to 300 mg/day; 150 to 300 to 450 mg/day; 150 to 300 to 450 to 600 mg/day; 150 to 300 to 600 mg/day; 300 to 600 mg/day. Pain outcomes assessed for each group at each new dose were proportion of 30% and 50% responders (≥30% or ≥50% reduction in mean pain score from baseline) and mean change in pain score. Percent change in mean pain score from baseline was assessed using a marginal structural model.

Results

Seven hundred and sixty-one patients treated with flexible-dose pregabalin were included in the analysis. For each dose pathway group, there was a notably greater proportion of 30% and 50% responders and change in pain score, at each escalating dose. As assessed by the marginal structural model, higher doses of pregabalin were estimated to result in a significantly greater change in mean pain score at each week. This dose response with flexible-dose pregabalin was consistent with that previously observed with fixed-dose pregabalin.

Conclusion

Many patients who do not respond to lower doses of pregabalin will respond with notable improvements in pain outcomes when the dose is escalated. These data should encourage physicians treating patients with neuropathic pain to escalate pregabalin to the dose that delivers optimal analgesia and tolerable side effects.

Neuropathic Pain and Spinal Cord Injury: Phenotypes and Pharmacological Management

Chronic neuropathic pain is a complicated condition after a spinal cord injury (SCI) that often has a lifelong and significant negative impact on life after the injury; therefore, improved pain management is considered a significant and unmet need. Neuropathic pain mechanisms are heterogeneous and the difficulty in determining their individual contribution to specific pain types may contribute to poor treatment outcomes in this population. Thus, identifying human neuropathic pain phenotypes based on pain symptoms, somatosensory changes, or cognitive and psychosocial factors that reflect specific spinal cord or brain mechanisms of neuropathic pain is an important goal. Once a pain phenotype can be reliably replicated, its relationship with biomarkers and clinical treatment outcomes can be analyzed, and thereby facilitate translational research and further the mechanistic understanding of individual differences in the pain experience and in clinical trial outcomes. The present article will discuss clinical aspects of SCI-related neuropathic pain, neuropathic pain phenotypes, pain mechanisms, potential biomarkers and pharmacological interventions, and progress regarding how defining neuropathic pain phenotypes may lead to more targeted treatments for these difficult pain conditions.

Hypercapnia Caused by a Therapeutic Dosage of Pregabalin in a Tetraplegic Patient With Cervical Spinal Cord Injury

Pregabalin is often used for the treatment of neuropathic pain in patients with spinal cord injury (SCI). We reported a patient with C5 [S(C5/C6)] ASIA Impairment Scale C SCI due to cervical myelopathy who presented CO2 retention when taking a therapeutic dosage of pregabalin. An 88-year-old patient with cervical SCI was transferred to the department of physical medicine and rehabilitation. When he had transferred, his neuropathic pain had been treated with 150-mg pregabalin per day (75 mg twice a day); however, he still exhibited severe neuropathic pain with a Numeric Pain Rating Scale score of 7 to 8. Dosage for the pregabalin increased from 150 mg/d (75 mg twice a day) to 225 mg/d (150 mg at morning and 75 mg at dinner). That afternoon, he presented drowsiness and confusion, and arterial blood gas analysis (ABGA) demonstrated respiratory acidosis with CO2 retention; pH, 7.312; PaCO2, 62.8 mm Hg; PaO2,58.9 mm Hg; HCO3 concentration, 30.8 mmol/L; base excess, 3.2 mmol/L; and oxygen saturation, 90.4%. Finally, he required tracheal intubation and ventilation. After 6 weeks, the patient was transferred to a general ward, and the follow-up ABGA and end-tidal CO2 showed normal range with the discontinuation of pregabalin. We demonstrated CO2 retention via ABGA in a patient with SCI due to cervical myelopathy who developed hypercapnia after taking a therapeutic dose of pregabalin. Physicians should pay particular attention to CO2 retention when prescribing a therapeutic dosage of pregabalin in a patient with cervical SCI.

Effectiveness of low-dose pregabalin in three patients with Lewy body disease and central neuropathic pain

Many patients with Lewy body disease complain of pain, and their pain may be associated with this disease. Recently, pain has become a focus of attention in Parkinson's disease, but there is little information regarding pain in patients who have dementia with Lewy bodies. We used pregabalin to treat three Lewy body disease patients with chronic pain that may have been related to degeneration of central neurons. All three patients responded well to pregabalin at 25-50 mg/day. To our knowledge, there have been no previous reports of pregabalin showing efficacy for central neuropathic pain in Parkinson's disease or Lewy body disease.

Pregabalin for Neuropathic Pain: Why Benefits Could Be Expected for Multiple Pain Conditions

BACKGROUND AND OBJECTIVE

Limited research exists to support the extrapolation of the analgesic efficacy of pregabalin from one neuropathic pain condition to another. This retrospective analysis evaluated similarities in the efficacy of pregabalin for treating neuropathic pain associated with post-herpetic neuralgia (PHN), diabetic peripheral neuropathy (DPN), and spinal cord injury (SCI) in a Japanese population, as a basis for considering the extrapolation of these data to other neuropathic pain conditions.

METHODS

Data were analysed across pregabalin doses within each pain condition, from three comparable 13- to 16-week, randomized, double-blind, placebo-controlled trials (RCTs) and the corresponding 52-week, open-label extension trials of pregabalin in Japanese patients with PHN, DPN or SCI. Efficacy outcomes in the RCTs included endpoint and weekly mean pain and sleep interference scores; endpoint proportions of responders in pain; Patient Global Impression of Change scores; and 36-Item Short Form Health Survey (SF-36) scores or Hospital Anxiety and Depression Scale (HADS) assessments. Study discontinuation rates were compared between treatment groups. The extension trials assessed pain intensity, using the Short-Form McGill Pain Questionnaire.

RESULTS

In the RCTs for all pain conditions, significant improvements in comparison with placebo in mean pain and sleep interference scores were evident after 1 week with pregabalin and were sustained throughout the treatment periods (p < 0.05). At the study endpoint, in comparison with placebo, a significantly greater percentage of pregabalin-treated patients experienced a ≥30 % reduction in pain across the RCTs (p < 0.05), and pregabalin significantly improved six of 16 SF-36 subscale scores in the PHN and DPN trials (p < 0.05). In the SCI trial, pregabalin-treated patients had numerically better outcomes of HADS scores. In the extension trials, improvements in pain intensity were maintained over a 52-week period.

CONCLUSION

Similarities in the pregabalin efficacy profiles, including time to onset and magnitude of response, were confirmed regardless of the neuropathic pain condition. These data support the potential for extrapolating analgesic efficacy to other neuropathic pain conditions. CLINICALTRIALS.

GOV IDENTIFIERS

NCT00394901, NCT00553475, NCT00407745, NCT00424372, NCT00553280, NCT01202227.

Pregabalin in Patients With Painful Diabetic Peripheral Neuropathy Using an NSAID for Other Pain Conditions: A Double-Blind Crossover Study

OBJECTIVES

To evaluate pregabalin's efficacy and safety versus placebo to reduce pain in patients with diabetic peripheral neuropathy (DPN) using a concomitant nonsteroidal anti-inflammatory drug.

MATERIALS AND METHODS

In a randomized, double-masked, 14-week, 2-period, crossover study, patients with painful DPN using a nonsteroidal anti-inflammatory drug for non-DPN-related pain received 150 to 300 mg/d pregabalin or placebo (period 1); 14-day washout; then, the opposite therapy (period 2). Endpoints included weekly change in DPN pain score, sleep interference, adverse events, and patient-reported outcomes.

RESULTS

Patients with similar baseline characteristics were randomized (period 1) to 1 of the 2 following possible sequences: pregabalin→placebo (n=154) or placebo→pregabalin (n=147). Results of the primary efficacy measure, mean weekly DPN pain at endpoint, showed no significant difference between pregabalin and placebo. However, 1 sensitivity analysis (mixed-model repeated measures) found greater pain score reductions with pregabalin than placebo at weeks 2 to 4 and overall (all P<0.05). One secondary endpoint analysis, mean treatment difference in DPN-related sleep interference, favored pregabalin over placebo (P=0.0009). Other sensitivity and secondary analyses were nonsignificant. Treatment-emergent adverse events were consistent with the known safety profile of pregabalin.

DISCUSSION

Pregabalin (vs. placebo) showed overall improvements in sleep, pain reduction in 1 sensitivity analysis, and was well tolerated. Potential factors that may have confounded the ability to detect a treatment difference in DPN pain reduction (high placebo response, carryover effect, short washout period, or pregabalin dose) are discussed in the context of future studies.

Improvement in pain severity category in clinical trials of pregabalin

BACKGROUND

Pregabalin is approved by the US Food and Drug Administration for the treatment of fibromyalgia (FM), diabetic peripheral neuropathy (DPN), postherpetic neuralgia (PHN), and neuropathic pain due to spinal cord injury (SCI). Approval was based on clinical trial data demonstrating statistically significant differences in pain scores versus placebo. However, statistically significant pain relief may not always equate to clinically meaningful pain relief. To further characterize the clinical benefit of pregabalin, this analysis examined shifts in pain severity categories in patients with FM, DPN/PHN (pooled in this analysis), and SCI treated with pregabalin.

METHODS

Data were pooled from 23 placebo-controlled trials in patients with FM (1,623 treated with pregabalin, 937 placebo), DPN/PHN (2,867 pregabalin, 1,532 placebo), or SCI (181 pregabalin, 175 placebo). Pain scores were assessed on an 11-point numeric rating scale and categorized as mild (0 to <4), moderate (4 to <7), or severe (7 to 10). Only patients with mean score ≥4 at baseline were randomized to treatment. The percentage of patients shifting pain category from baseline to endpoint for pregabalin and placebo was analyzed using a modified ridit transformation with the Cochran-Mantel-Haenszel procedure.

RESULTS

A higher proportion of patients shifted to a less severe pain category at endpoint with pregabalin compared with placebo. With flexible-dose pregabalin, the percentage of patients improving from: severe to mild (pregabalin versus placebo) was 15.8 versus 13.4 in FM patients, 36.0 versus 16.6 in DPN/PHN patients, 14.3 versus 7.7 in SCI patients; severe to moderate was 28.7 versus 28.2 in FM patients, 32.5 versus 28.2 in DPN/PHN patients, 35.7 versus 28.2 in SCI patients; and moderate to mild was 38.3 versus 26.4 in FM patients, 59.5 versus 41.4 in DPN/PHN patients, 38.6 versus 27.2 in SCI patients.

CONCLUSION

Compared with placebo, pregabalin is more often associated with clinically meaningful improvements in pain category in patients with FM, DPN, PHN, or SCI.

Symptom-Based Treatment of Neuropathic Pain in Spinal Cord-Injured Patients: A Randomized Crossover Clinical Trial

OBJECTIVE

The objective of this study was to identify the differences in medication effect according to pain characteristics in spinal cord-injured patients.

METHODS

This study is a prospective, randomized, crossover study. Fifty-five patients and 66 locations of neuropathic pain were included. Pain was classified into four spontaneous characteristics and three evoked pain characteristics. Oxcarbazepine (Na channel blocker) and pregabalin (calcium channel α2-δ ligand medication) were tried. Patients were divided into two groups: evoked pain present and evoked pain absent. Overall average visual analog scale was obtained.

RESULTS

Oxcarbazepine was significantly more effective for patients without evoked pain than in those with it for electrical, burning, and pricking pain. The effect of pregabalin was not different regarding the presence or absence of evoked pain for all pain categories, except burning pain. In patients with evoked pain, pregabalin was shown to be significantly more effective for electrical pain, allodynia, and heat hyperalgesia than oxcarbazepine. In the evoked pain absent group, oxcarbazepine showed greater improvement than pregabalin but was not significant.

CONCLUSIONS

In summary, the phenotype of neuropathic pain was associated with the efficacy of different pharmacologic treatments. Symptom-based treatment, therefore, can lead to more efficient analgesia.

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.

Transcranial magnetic stimulation of the brain: guidelines for pain treatment research

Recognizing that electrically stimulating the motor cortex could relieve chronic pain sparked development of noninvasive technologies. In transcranial magnetic stimulation (TMS), electromagnetic coils held against the scalp influence underlying cortical firing. Multiday repetitive transcranial magnetic stimulation (rTMS) can induce long-lasting, potentially therapeutic brain plasticity. Nearby ferromagnetic or electronic implants are contraindications. Adverse effects are minimal, primarily headaches. Single provoked seizures are very rare. Transcranial magnetic stimulation devices are marketed for depression and migraine in the United States and for various indications elsewhere. Although multiple studies report that high-frequency rTMS of the motor cortex reduces neuropathic pain, their quality has been insufficient to support Food and Drug Administration application. Harvard's Radcliffe Institute therefore sponsored a workshop to solicit advice from experts in TMS, pain research, and clinical trials. They recommended that researchers standardize and document all TMS parameters and improve strategies for sham and double blinding. Subjects should have common well-characterized pain conditions amenable to motor cortex rTMS and studies should be adequately powered. They recommended standardized assessment tools (eg, NIH's PROMIS) plus validated condition-specific instruments and consensus-recommended metrics (eg, IMMPACT). Outcomes should include pain intensity and qualities, patient and clinician impression of change, and proportions achieving 30% and 50% pain relief. Secondary outcomes could include function, mood, sleep, and/or quality of life. Minimum required elements include sample sources, sizes, and demographics, recruitment methods, inclusion and exclusion criteria, baseline and posttreatment means and SD, adverse effects, safety concerns, discontinuations, and medication-usage records. Outcomes should be monitored for at least 3 months after initiation with prespecified statistical analyses. Multigroup collaborations or registry studies may be needed for pivotal trials.

Lipoxin A4 inhibits microglial activation and reduces neuroinflammation and neuropathic pain after spinal cord hemisection

BACKGROUND

Spinal cord injury (SCI) is a severe neurological disorder with many disabling consequences, including persistent neuropathic pain, which develops in about 40 % of SCI patients and is induced and sustained by excessive and uncontrolled spinal neuroinflammation. Here, we have evaluated the effects of lipoxin A4 (LXA4), a member of a unique class of endogenous lipid mediators with both anti-inflammatory and analgesic properties, on spinal neuroinflammation and chronic pain in an experimental model of SCI.

METHODS

Spinal hemisection at T10 was carried out in adult male CD1 mice and Wistar rats. To test if LXA4 can reduce neuroinflammation and neuropathic pain, each animal received two intrathecal injections of LXA4 (300 pmol) or vehicle at 4 and 24 h after SCI. Sensitivity to mechanical stimulation of the hind paws was evaluated using von Frey monofilaments, and neuroinflammation was tested by measuring the mRNA and/or protein expression levels of glial markers and cytokines in the spinal cord samples after SCI. Also, microglia cultures prepared from murine cortical tissue were used to assess the direct effects of LXA4 on microglial activation and release of pro-inflammatory TNF-α.

RESULTS

LXA4 treatment caused significant reductions in the intensity of mechanical pain hypersensitivity and spinal expression levels of microglial markers and pro-inflammatory cytokines induced by SCI, when compared to rodents receiving control vehicle injections. Notably, the increased expressions of the microglial marker IBA-1 and of the pro-inflammatory cytokine TNF-α were the most affected by the LXA4 treatment. Furthermore, cortical microglial cultures expressed ALX/FPR2 receptors for LXA4 and displayed potentially anti-inflammatory responses upon challenge with LXA4.

CONCLUSIONS

Collectively, our results suggest that LXA4 can effectively modulate microglial activation and TNF-α release through ALX/FPR2 receptors, ultimately reducing neuropathic pain in rodents after spinal cord hemisection. The dual anti-inflammatory and analgesic properties of LXA4, allied to its endogenous nature and safety profile, may render this lipid mediator as new therapeutic approach for treating various neuroinflammatory disorders and chronic pain with only limited side effects.

Central Neuropathic Pain Syndromes

Chronic pain is common in patients with neurologic complications of a central nervous system insult such as stroke. The pain is most commonly musculoskeletal or related to obligatory overuse of neurologically unaffected limbs. However, neuropathic pain can result directly from the central nervous system injury. Impaired sensory discrimination can make it challenging to differentiate central neuropathic pain from other pain types or spasticity. Central neuropathic pain may also begin months to years after the injury, further obscuring recognition of its association with a past neurologic injury. This review focuses on unique clinical features that help distinguish central neuropathic pain. The most common clinical central pain syndromes-central poststroke pain, multiple sclerosis-related pain, and spinal cord injury-related pain-are reviewed in detail. Recent progress in understanding of the pathogenesis of central neuropathic pain is reviewed, and pharmacological, surgical, and neuromodulatory treatments of this notoriously difficult to treat pain syndrome are discussed.

Spinal cord injury-induced pain: mechanisms and treatments

Pain is a common consequence of a spinal cord injury (SCI) and has a major impact on quality of life through its impact on physical function, mood and participation in work, recreational and social activities. Several types of pain typically present following SCI with central neuropathic pain being a frequent and difficult to manage occurrence. Despite advances in our understanding of the mechanisms contributing to this type of pain and an increasing number of trials examining treatment efficacy, our ability to relieve neuropathic SCI pain is still very limited. Optimal management relies upon an integrated approach that uses a combination of pharmacological and nonpharmacological options.

Nelson A, J. Avram M, Lee Robak S, T. Benzon H. Efficacy of Pregabalin in the Treatment of Radicular Pain: Results of a Controlled Trial

Background:

Pregabalin is commonly used to treat patients with various neuropathic pain syndromes.

Objectives:

The purpose of the present study was to evaluate the efficacy of pregabalin in patients with lumbar or cervical radicular pain.

Patients and Methods:

A prospective, randomized, double-blind trial was conducted in 39 patients with lumbar and cervical radicular pain, who received 3 weeks of either pregabalin (n = 10) or placebo (n = 9) treatment. Baseline pain and disability were evaluated before the treatment and were re-evaluated, along with overall patient satisfaction, after the 3 weeks of treatment.

Results:

Data on 19 of the 39 patients recruited were available for analysis. No statistically significant differences in the pain, disability, and patient satisfaction scores were found between the groups. When the individual patient scores were assessed, the placebo treatment was found to be efficacious in 4 of the 9 patients and pregabalin was effective in 2 of the 10 patients, but the difference was not statistically significant (P = 0.350).

Conclusions:

The present data do not suggest that pregabalin is more efficacious than placebo in the treatment of lumbar and cervical radicular pain. However, the small sample size of this study may have affected the ability to detect such a difference.

A retrospective study to identify risk factors for somnolence and dizziness in patients treated with pregabalin

Background

Pregabalin is a therapeutic drug for neuropathic pain that is associated with somnolence and dizziness. These adverse events are often experienced shortly after initiating pregabalin, and may lead to treatment discontinuation. The purpose of this study was to explore factors that influence the incidence of somnolence and dizziness induced by pregabalin, and to identify patients at higher risk of adverse events.

Methods

A retrospective analysis was conducted of patient characteristics (age, gender, renal function, initial daily dose of pregabalin, co-administration of strong opioids and hypnotics) and the incidence of somnolence and dizziness during the first week of pregabalin treatment. An electronic chart was used to collect data from 204 inpatients prescribed pregabalin at Nagoya University Hospital from June 2011 to November 2012.

Results

Among 36 patients who regularly received strong opioids, 18 (50.0 %) reported somnolence or dizziness during the first week of pregabalin treatment. The remaining 168 patients did not regularly receive strong opioids, and 25 (14.9 %) had an adverse event. In multivariate analysis, age (≧65 years, adjusted odds ratio: 2.507, 95 % CI: 1.164-5.397, p = 0.019) and regular co-administration of strong opioids (adjusted odds ratio: 5.507, 95 % CI: 2.460-12.328, p < 0.001) correlated with somnolence or dizziness.

Conclusions

These data suggest that age (≧65 years) and co-administration of strong opioids are risk factors for somnolence or dizziness during pregabalin treatment for neuropathic pain. More careful dose titration is recommended for elderly patients and those receiving concomitant strong opioids.

Temporal analysis of pain responders and common adverse events: when do these first appear following treatment with pregabalin

Background

Pregabalin is an α₂δ ligand indicated in the USA for treatment of a number of chronic pain conditions, including diabetic peripheral neuropathy, postherpetic neuralgia, pain associated with spinal cord injury, and fibromyalgia. A greater understanding of when patients first respond to treatment with pregabalin and when adverse events emerge, or worsen, could aid design of new proof-of-concept studies and help guide treatment of patients.

Methods

This was an analysis of five randomized, placebo-controlled, double-blind trials (between 8 and 16 weeks in duration) of flexible-dose pregabalin (150–600 mg/day). Individual patient data were pooled into three groups by disease condition: diabetic peripheral neuropathy or postherpetic neuralgia (n=514), spinal cord injury (n=356), and fibromyalgia (n=498). Responders were classified as having a ≥30% and/or ≥50% reduction in mean pain score from baseline; once a patient responded, they were not scored subsequently (and were excluded from the responder analysis). The emergence of adverse events at each week was also recorded.

Results

The majority of the 30% and 50% responders emerged within the first 3–4 weeks with pregabalin, but were more uniformly distributed across the 6 weeks of the analysis with placebo. The majority of common adverse events also emerged within the first 3–4 weeks of pregabalin treatment.

Conclusion

These data suggest that the majority of pain responders and common adverse events emerge within 3–4 weeks of treatment with pregabalin. These data could advise new proof-of-concept studies and guide clinical management.

Management of Neuropathic Pain Associated with Spinal Cord Injury

Spinal cord injury (SCI) is an injury to the spinal cord that leads to varying degrees of motor and/or sensory deficits and paralysis. Chronic pain of both neuropathic and nociceptive type is common and contributes to reduced quality of life. The aim of the review is to provide current clinical understanding as well as discuss and evaluate efficacy of pharmacological interventions demonstrated in the clinical studies. The review was based on literature search in PubMed and Medline with words "neuropathic pain" and "spinal cord injury". The review included clinical studies and not experimental data nor case reports. A limited number of randomized and placebo-controlled studies concerning treatment options of neuropathic pain after SCI were identified. Amitriptyline, a tricyclic antidepressant and the antiepileptic drugs, gabapentin and pregabalin, are most studied with demonstrated efficacy, and considered to be the primary choice. Opioids have demonstrated conflicting results in the clinical studies. In addition, administration route used in the studies as well as reported side effects restrict everyday use of opioids as well as ketamine and lidocaine. Topical applications of capsaicin or lidocaine as well as intradermal injections of Botulinum toxin are new treatment modalities that are so far not studied on SCI population and need further studies. Non-pharmacological approaches may have additional effect on neuropathic pain. Management of pain should always be preceded by thorough clinical assessment of the type of pain. Patients need a follow-up to evaluate individual effect of applied measures. However, the applied management does not necessarily achieve satisfactory pain reduction. Further clinical studies are needed to evaluate the effect of both established and novel management options.