Pregabalin for postherpetic neuralgia: placebo-controlled trial of fixed and flexible dosing regimens on allodynia and time to onset of pain relief

A Meta-analysis of Randomized Controlled Trials Comparing the Efficacy and Safety of Pregabalin and Gabapentin in the Treatment of Postherpetic Neuralgia

OBJECTIVE

To systematically evaluate the clinical efficacy of pregabalin and gabapentin in the treatment of postherpetic neuralgia (PHN), including the difference in pain control and occurrence of adverse reactions.

METHODS

PubMed, MEDLINE, EMBASE, Cochrane Library, and Web of Science databases were searched for randomized controlled trials (RCTs) comparing the efficacy of pregabalin and gabapentin in patients with PHN. Data from studies meeting the inclusion criteria were extracted and the Cochrane Risk of Bias risk assessment tool was used to evaluate the quality of the included studies. Revman 5.3 and Stata17 were used to perform the meta-analysis and to detect publication bias.

RESULTS

A total of 14 RCTs with 3545 patients were included in this study, including 926 in the pregabalin treatment group, 1256 in the gabapentin treatment group, and 1363 in the placebo control group. Pregabalin was better than gabapentin in alleviating pain and improving the global perception of change in pain and sleep (P < 0.05). Gabapentin was associated with a lower incidence of adverse events than pregabalin (P < 0.05). Funnel plot and Begg's and Egger's tests showed no significant publication bias.

CONCLUSION

Pregabalin appears to have a better overall therapeutic effect than gabapentin for patients with PHN, but gabapentin has a lower incidence of adverse reactions and a better safety profile. Clinicians should comprehensively consider patient factors and fully evaluate the advantages and disadvantages of each treatment option to select the most suitable drugs for patient use. Considering the limited quantity and quality of the existing literature, high-quality RCTs are needed to confirm the advantages of pregabalin over gabapentin in the treatment of PHN and guide clinical decision-making.

The risk of fragility fractures following initiation of gabapentin and pregabalin-A Danish, nationwide, high-dimensional propensity score-matched cohort study

Gabapentin and pregabalin have been associated with an increased risk of fragility fractures. Due to differences in pharmacokinetics, we aimed to assess the fracture-risk difference between the two medicines. We performed a Danish nationwide new user, high-dimensional propensity score-matched cohort study to assess the 90-day risk of fragility fractures among adults, from January 1996 to December 2018. We applied a high-dimensional propensity score to match new users of gabapentin with new users of pregabalin in a 1:1 intention-to-treat approach. Hazard ratios (HRs), incidence rates (IRs) and incidence rate difference (IRD) were obtained. We identified 388 236 eligible patients of which 294 223 and 98 869 initiated gabapentin and pregabalin, respectively. We included 48 272 matched pairs for further analysis. The mean age was 56 (IQR 44-69) years, and the average follow-up was approximately 11 500 person-years (PY). The IRs of fragility fractures were 23.7 (95%CI 21.0-26.7) and 23.2 (95%CI 20.5-26.2) per 1000 PY for gabapentin and pregabalin-exposed patients, respectively. This yielded an HR of 1.02 (95%CI 0.86-1.21) when using gabapentin as the intervention drug and pregabalin as the reference drug. The IRD was estimated to 0.5 PY (95%CI -3.5-4.5). In conclusion, short-term risk of fragility fractures among gabapentin initiators was not different compared to those initiating pregabalin.

Phenotypes and Genotypes in Postherpetic Neuralgia Drug Therapy: A Narrative Mini-review

Neuropathic pain is a debilitating symptom reported by patients presenting with postherpetic neuralgia (PHN). Efforts to alleviate this pain have been projected to lie in individualization of pharmacological treatment through pain phenotyping and subsequent investigations into the genetic basis of PHN therapy. Understanding the various mechanisms related to these phenotypes can aid in improvement of available treatment options and discovery of new ones. Knowledge and application of genetic variations in PHN, structural proteins, and genes can aid in ascertaining risk, susceptibility to, severity of, and protection from PHN. This review summarizes the most recent information that has been published on phenotypes and genotypes with possible clinical applications and directions for future research.

Xiaoketongbi Formula vs pregabalin for painful diabetic neuropathy: A single-center, randomized, single-blind, double-dummy, and parallel controlled clinical trial

BACKGROUND

We assessed the efficacy and safety of the Xiaoketongbi Formula (XF) vs. pregabalin in patients with painful diabetic neuropathy (PDN).

METHODS

Patients with PDN (n = 68) were included in a single-center, randomized, single-blind, double-dummy, parallel controlled clinical trial. The primary outcome was the change in the Brief Pain Inventory for Diabetic Peripheral Neuropathy (BPI-DPN). Secondary outcomes evaluated included the reduction of BPI-DPN >50%, changes in the numeric rating scale-11 (NRS-11) score for pain, Daily Sleep Interference Diary (DSID), Patient Global Impression of Change (PGIC), nerve conduction velocity (NCV), and adverse events.

RESULTS

After 10 weeks of treatment, the BPI-DPN score reduced from 42.44 ± 17.56 to 26.47 ± 22.22 and from 52.03 ± 14.30 to 37.85 ± 17.23 in the XF and pregabalin group (Ps  < 0.001), respectively. The difference in the absolute change in BPI-DPN score between both groups was -1.79 (95% CI: -9.09, 5.50; p = 0.625). In the XF and pregabalin groups, 44.1% (15/34) and 20.6% (7/34) of patients reported a BPI-DPN reduction >50% (p = 0.038), respectively. There were no significant differences between groups in NRS-11 and DSID (Ps  > 0.05). A significantly greater number of patients in the XF group felt "significantly improved" or "improved" than in the pregabalin group (35.3% (12/34) vs. 11.8% (4/34), p = 0.045). The absolute change in motor nerve conduction velocity of the right median nerve was significantly different between both groups (XF group 0.7 ± 2.3 vs. pregabalin group -2.2 ± 4.1, p = 0.004). No serious adverse events were reported in either group.

CONCLUSIONS

XF is equivalent to pregabalin in reducing pain symptoms and improves the quality of life in patients with PDN. In addition, XF has the potential to improve nerve function by increasing NCV.

The current clinical use of adjuvant analgesics for refractory cancer pain in Japan: a nationwide cross-sectional survey

BACKGROUND

Although adjuvant analgesics are used to treat opioid-refractory cancer pain, there is insufficient evidence to support this practice and limited data to guide the choice depending on cancer pain pathophysiology, dose titration and starting dose. This survey aimed to clarify the current use of adjuvant analgesics for treating opioid-refractory cancer pain.

METHODS

In this cross-sectional study, we sent an online survey questionnaire to 208 certified palliative care specialists. Primary outcomes were (i) effective pathophysiological mechanism of cancer pain and (ii) initiating doses and time period to the first response to each adjuvant analgesic therapy.

RESULTS

In total, 87 (42%) palliative care specialists responded. Of all patients with cancer pain, 40% of patients (median) with refractory cancer pain were prescribed adjuvant analgesics. Additionally, 94.3, 93.1 and 86.2% of palliative care specialists found dexamethasone/betamethasone effective for neuropathic pain caused by tumor-related spinal cord compression, pregabalin effective for malignant painful radiculopathy and dexamethasone/betamethasone effective for brain tumor or leptomeningeal metastases-related headache, respectively. The median starting dose of pregabalin, dexamethasone/betamethasone, lidocaine and ketamine were 75, 4, 200, and 50 mg/day, respectively, and the median time to the first response of those medications were 5, 3, 2 and 3 days, respectively.

CONCLUSIONS

Many palliative care specialists select adjuvant analgesics depending on the pathophysiological mechanism of cancer pain in each case. They used such adjuvant analgesics in low doses for cancer pain with short first-response periods.

Design and conduct of confirmatory chronic pain clinical trials

The purpose of this article is to provide readers with a basis for understanding the emerging science of clinical trials and to provide a set of practical, evidence-based suggestions for designing and executing confirmatory clinical trials in a manner that minimizes measurement error. The most important step in creating a mindset of quality clinical research is to abandon the antiquated concept that clinical trials are a method for capturing data from clinical practice and shifting to a concept of the clinical trial as a measurement system, consisting of an interconnected set of processes, each of which must be in calibration for the trial to generate an accurate and reliable estimate of the efficacy (and safety) of a given treatment. The status quo of inaccurate, unreliable, and protracted clinical trials is unacceptable and unsustainable. This article gathers aspects of study design and conduct under a single broad umbrella of techniques available to improve the accuracy and reliability of confirmatory clinical trials across traditional domain boundaries.

Treatment Response to Gabapentin in Neuropathic Ocular Pain Associated with Dry Eye

PURPOSE

To investigate the response to gabapentin treatment in patients with dry eye (DE) accompanied by features of neuropathic ocular pain (NOP), and to analyze the differences between clinical manifestations of the groups according to treatment response.

METHODS

We retrospectively reviewed the records of 35 patients with DE accompanied by NOP features and obtained information on their medical history and previous ocular history. The patients underwent clinical examinations of the tear film, ocular surface, and meibomian gland and completed the Ocular Pain Assessment Survey (OPAS). One month after treatment with topical eye drops, add-on of gabapentin treatment was determined according to the Wong-Baker FACES Pain Rating Scale (WBFPS). A reduction of 2 points or more on the WBFPS was considered a positive treatment response. Enrolled patients were divided into three groups according to the treatment response: topical treatment response group (group 1, n = 11); gabapentin response group (group 2, n = 13); and gabapentin non-response group (group 3, n = 11). The medical history, clinical parameters, and OPAS scores were compared between groups.

RESULTS

The incidence of systemic comorbidities was higher in group 2 than in other groups. The corneal staining scores were lower in groups 2 and 3 than in group 1. Among the treatment response groups, group 2 showed improvements in OPAS scores of ocular pain severity, pain other than eyes, and quality of life, while group 1 showed improved OPAS scores of ocular pain severity and ocular associated factors. Group 2 exhibited lower scores of pains aggravated by mechanical and chemical stimuli than group 3.

CONCLUSIONS

Gabapentin could be effective in patients who have systemic comorbidity and less pain evoked by mechanical and chemical stimuli for the treatment of DE patients with NOP, which is refractory to topical treatment.

Systematic review and network meta-analysis of the efficacy and safety of lidocaine 700 mg medicated plaster vs. pregabalin

Objective: Neuropathic pain prevalence is estimated between 7% and 10% of the population. International guidelines recommend a variety of drugs at different therapy lines for pain relief. However, side effect profiles, for example, prompted the UK government recently to classify pregabalin and gabapentin as class C drugs. Lidocaine 700 mg medicated plaster (LMP) might be a safer alternative. A systematic review assessed how LMP and pregabalin compared in terms of efficacy and safety. The review focused on pain reduction, quality of life and adverse events in peripheral neuropathic pain (PNP) i.e. post-herpetic neuralgia, diabetic peripheral neuropathy, post-surgical/trauma, or other PNP conditions.Methods: Electronic databases were searched as well as a number of other sources up to November 2018. Sensitive strategies were used, with no restriction by language or publication status. Two independent reviewers screened records and extracted data with consensus determining final decisions. Risk of bias was assessed using the Cochrane Collaboration 2011 checklist for RCTs. Full network meta-analysis was conducted to compare LMP to pregabalin 300/600 mg in terms of pain reduction, quality of life, as well as serious adverse events and selected adverse events. Trials with enriched enrolment design were excluded.Results: Searches retrieved 7,104 records. In total 111 references pertaining to 43 RCTs were included for data extraction. Bayesian network meta-analysis of several pain outcomes showed no clear difference in efficacy between treatments However, LMP was clearly advantageous in terms of dizziness and any adverse event vs. pregabalin 600 mg/day and discontinuations vs. pregabalin 300 mg/day or 600 mg/day, as well as being associated with improved quality of life (albeit in this case based on weak evidence).Conclusions: LMP was found to be similar to pregabalin in reducing pain in all populations but had a better adverse events profile.

The relationship between the reporting of euphoria events and early treatment responses to pregabalin: an exploratory post-hoc analysis

Background

Euphoria is a complex, multifactorial problem that is reported as an adverse event in clinical trials of analgesics including pregabalin. The relationship between the reporting of euphoria events and pregabalin early treatment responses was examined in this exploratory post-hoc analysis.

Methods

Data were from patients with neuropathic or non-neuropathic chronic pain enrolled in 40 randomized clinical trials, who received pregabalin (75–600 mg/day) or placebo. Reports of treatment-emergent euphoria events were based on the Medical Dictionary of Regulatory Activities preferred term “euphoric mood”. Prevalence rates of euphoria events overall and by indication were assessed. Post-treatment endpoints included ≥30% improvements in pain and sleep scores up to 3 weeks as well as a ≥1-point improvement in daily pain score up to 11 days after treatment.

Results

13,252 patients were analyzed; 8,501 (64.1%) and 4,751 (35.9%) received pregabalin and placebo, respectively. Overall, 1.7% (n=222) of patients reported euphoria events. Among pregabalin-treated patients, a larger proportion who reported euphoria events achieved an early pain response compared with those who did not report euphoria (30% pain responders in week 1 with euphoria events [43.0%], without euphoria events [24.2%]). Results were similar for weeks 2 and 3. For Days 2–11, a larger proportion of pregabalin-treated patients with (relative to without) euphoria events were 1-point pain responders. Findings were similar in pregabalin-treated patients for sleep endpoints (30% sleep responders in week 1 with euphoria events [50.7%], without euphoria events [36.1%]). Similar results were found for weeks 2 and 3. Patients who received placebo showed similar patterns, although the overall number of them who reported euphoria events was small (n=13).

Conclusion

In patients who received pregabalin for neuropathic or non-neuropathic chronic pain, those who experienced euphoria events may have better early treatment responses than those who did not report euphoria events.

Pregabalin for neuropathic pain in adults

BACKGROUND

This review updates part of an earlier Cochrane Review titled "Pregabalin for acute and chronic pain in adults", and considers only neuropathic pain (pain from damage to nervous tissue). Antiepileptic drugs have long been used in pain management. Pregabalin is an antiepileptic drug used in management of chronic pain conditions.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of pregabalin for chronic neuropathic pain in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase for randomised controlled trials from January 2009 to April 2018, online clinical trials registries, and reference lists.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing pregabalin (any route of administration) with placebo or another active treatment for neuropathic pain, with participant-reported pain assessment.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and biases. Primary outcomes were: at least 30% pain intensity reduction over baseline; much or very much improved on the Patient Global Impression of Change (PGIC) Scale (moderate benefit); at least 50% pain intensity reduction; or very much improved on PGIC (substantial benefit). We calculated risk ratio (RR) and number needed to treat for an additional beneficial (NNTB) or harmful outcome (NNTH). We assessed the quality of the evidence using GRADE.

MAIN RESULTS

We included 45 studies lasting 2 to 16 weeks, with 11,906 participants - 68% from 31 new studies. Oral pregabalin doses of 150 mg, 300 mg, and 600 mg daily were compared with placebo. Postherpetic neuralgia, painful diabetic neuropathy, and mixed neuropathic pain predominated (85% of participants). High risk of bias was due mainly to small study size (nine studies), but many studies had unclear risk of bias, mainly due to incomplete outcome data, size, and allocation concealment.Postherpetic neuralgia: More participants had at least 30% pain intensity reduction with pregabalin 300 mg than with placebo (50% vs 25%; RR 2.1 (95% confidence interval (CI) 1.6 to 2.6); NNTB 3.9 (3.0 to 5.6); 3 studies, 589 participants, moderate-quality evidence), and more had at least 50% pain intensity reduction (32% vs 13%; RR 2.5 (95% CI 1.9 to 3.4); NNTB 5.3 (3.9 to 8.1); 4 studies, 713 participants, moderate-quality evidence). More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (62% vs 24%; RR 2.5 (95% CI 2.0 to 3.2); NNTB 2.7 (2.2 to 3.7); 3 studies, 537 participants, moderate-quality evidence), and more had at least 50% pain intensity reduction (41% vs 15%; RR 2.7 (95% CI 2.0 to 3.5); NNTB 3.9 (3.1 to 5.5); 4 studies, 732 participants, moderate-quality evidence). Somnolence and dizziness were more common with pregabalin than with placebo (moderate-quality evidence): somnolence 300 mg 16% versus 5.5%, 600 mg 25% versus 5.8%; dizziness 300 mg 29% versus 8.1%, 600 mg 35% versus 8.8%.Painful diabetic neuropathy: More participants had at least 30% pain intensity reduction with pregabalin 300 mg than with placebo (47% vs 42%; RR 1.1 (95% CI 1.01 to 1.2); NNTB 22 (12 to 200); 8 studies, 2320 participants, moderate-quality evidence), more had at least 50% pain intensity reduction (31% vs 24%; RR 1.3 (95% CI 1.2 to 1.5); NNTB 22 (12 to 200); 11 studies, 2931 participants, moderate-quality evidence), and more had PGIC much or very much improved (51% vs 30%; RR 1.8 (95% CI 1.5 to 2.0); NNTB 4.9 (3.8 to 6.9); 5 studies, 1050 participants, moderate-quality evidence). More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (63% vs 52%; RR 1.2 (95% CI 1.04 to 1.4); NNTB 9.6 (5.5 to 41); 2 studies, 611 participants, low-quality evidence), and more had at least 50% pain intensity reduction (41% vs 28%; RR 1.4 (95% CI 1.2 to 1.7); NNTB 7.8 (5.4 to 14); 5 studies, 1015 participants, low-quality evidence). Somnolence and dizziness were more common with pregabalin than with placebo (moderate-quality evidence): somnolence 300 mg 11% versus 3.1%, 600 mg 15% versus 4.5%; dizziness 300 mg 13% versus 3.8%, 600 mg 22% versus 4.4%.Mixed or unclassified post-traumatic neuropathic pain: More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (48% vs 36%; RR 1.2 (1.1 to 1.4); NNTB 8.2 (5.7 to 15); 4 studies, 1367 participants, low-quality evidence), and more had at least 50% pain intensity reduction (34% vs 20%; RR 1.5 (1.2 to 1.9); NNTB 7.2 (5.4 to 11); 4 studies, 1367 participants, moderate-quality evidence). Somnolence (12% vs 3.9%) and dizziness (23% vs 6.2%) were more common with pregabalin.Central neuropathic pain: More participants had at least 30% pain intensity reduction with pregabalin 600 mg than with placebo (44% vs 28%; RR 1.6 (1.3 to 2.0); NNTB 5.9 (4.1 to 11); 3 studies, 562 participants, low-quality evidence) and at least 50% pain intensity reduction (26% vs 15%; RR 1.7 (1.2 to 2.3); NNTB 9.8 (6.0 to 28); 3 studies, 562 participants, low-quality evidence). Somnolence (32% vs 11%) and dizziness (23% vs 8.6%) were more common with pregabalin.Other neuropathic pain conditions: Studies show no evidence of benefit for 600 mg pregabalin in HIV neuropathy (2 studies, 674 participants, moderate-quality evidence) and limited evidence of benefit in neuropathic back pain or sciatica, neuropathic cancer pain, or polyneuropathy.Serious adverse events, all conditions: Serious adverse events were no more common with placebo than with pregabalin 300 mg (3.1% vs 2.6%; RR 1.2 (95% CI 0.8 to 1.7); 17 studies, 4112 participants, high-quality evidence) or pregabalin 600 mg (3.4% vs 3.4%; RR 1.1 (95% CI 0.8 to 1.5); 16 studies, 3995 participants, high-quality evidence).

AUTHORS' CONCLUSIONS

Evidence shows efficacy of pregabalin in postherpetic neuralgia, painful diabetic neuralgia, and mixed or unclassified post-traumatic neuropathic pain, and absence of efficacy in HIV neuropathy; evidence of efficacy in central neuropathic pain is inadequate. Some people will derive substantial benefit with pregabalin; more will have moderate benefit, but many will have no benefit or will discontinue treatment. There were no substantial changes since the 2009 review.

Benefits and harms of pregabalin in the management of neuropathic pain: a rapid review and meta-analysis of randomised clinical trials

OBJECTIVE

To assess the benefits and harms of pregabalin in the management of neuropathic pain.

DESIGN

Rapid review and meta-analysis of phase III, randomised, placebo-controlled trials.

PARTICIPANTS

Adults aged 18 years and above with neuropathic pain defined according to the International Association for the Study of Pain criteria.

INTERVENTIONS

Pregabalin or placebo.

PRIMARY AND SECONDARY OUTCOME MEASURES

Our primary outcomes were pain (as measured using validated scales) and adverse events. Our secondary outcomes were sleep disturbance, quality of life, Patient Global Impression of Change, Clinician Global Impression scale, anxiety and depression scores, overall discontinuations and discontinuations because of adverse events.

RESULTS

We included 28 trials comprising 6087 participants. The neuropathic pain conditions studied were diabetic peripheral neuropathy, postherpetic neuralgia, herpes zoster, sciatica (radicular pain), poststroke pain and spinal cord injury-related pain. Patients who took pregabalin reported significant reductions in pain (numerical rating scale (NRS)) compared with placebo (standardised mean difference (SMD) -0.49 (95% CI -0.66 to -0.32, p<0.00001), very low quality evidence). Pregabalin significantly reduced sleep interference scores (NRS) compared with placebo (SMD -0.38 (95% CI -0.50 to -0.26, p<0.00001), moderate quality evidence. Pregabalin significantly increased the risk of adverse events compared with placebo (RR 1.33 (95% CI 1.23 to 1.44, p<0.00001, low quality evidence)). The risks of experiencing weight gain, somnolence, dizziness, peripheral oedema, fatigue, visual disturbances, ataxia, non-peripheral oedema, vertigo and euphoria were significantly increased with pregabalin. Pregabalin was significantly more likely than placebo to lead to discontinuation of the drug because of adverse events (RR 1.91 (95% CI 1.54 to 2.37, p<0.00001), low quality evidence).

CONCLUSION

Pregabalin has beneficial effects on some symptoms of neuropathic pain. However, its use significantly increases the risk of a number of adverse events and discontinuation due to adverse events. The quality of the evidence from journal publications is low.

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.

Efficacy and Safety of Once-Daily Controlled-Release Pregabalin for the Treatment of Patients With Postherpetic Neuralgia: A Double-Blind, Enriched Enrollment Randomized Withdrawal, Placebo-Controlled Trial

OBJECTIVES

To assess efficacy and safety of once-daily controlled-release (CR) formulation of pregabalin in patients with postherpetic neuralgia.

METHODS

An enriched enrollment, randomized withdrawal trial, with 6-week single-blind pregabalin treatment phase and 13-week double-blind phase, where patients with ≥50% decrease in mean pain score at single-blind end point from baseline were randomized (1:1) to pregabalin CR (82.5 to 660 mg/d) or placebo. Primary efficacy outcome was time to loss of therapeutic response (LTR) (<30% decrease in weekly mean pain score from single-blind baseline or discontinuation due to adverse event or lack of efficacy). Secondary efficacy outcomes included change in weekly mean pain score (1-wk recall period) at double-blind end point.

RESULTS

In total, 801 patients were randomized and treated in the single-blind phase, and 413 in the double-blind phase (208, pregabalin CR; 205, placebo). Pregabalin CR significantly increased time to LTR versus placebo (Kaplan-Meier analysis) with significantly fewer LTR events with pregabalin CR than with placebo (29 [13.9%] vs. 63 [30.7%]; P<0.0001). Median time to LTR was not estimable. Pregabalin CR significantly improved weekly mean pain score versus placebo: LS mean difference (95% CI) of -1.11 (-1.47, -0.75) and -1.00 (-1.34, -0.65) (P<0.0001) from single-blind baseline and double-blind baseline, respectively. Most commonly reported adverse events in the single-blind phase were dizziness, somnolence, and peripheral edema. Pregabalin CR was well tolerated.

DISCUSSION

Time to LTR was significantly longer with pregabalin CR than with placebo. Safety profile of pregabalin CR was comparable to that reported for the immediate-release formulation in patients with postherpetic neuralgia.

Superiority of capsaicin 8% patch versus oral pregabalin on dynamic mechanical allodynia in patients with peripheral neuropathic pain

Background

Dynamic Mechanical Allodynia (DMA) is a typical symptom of neuropathic pain (NP). In a recent study, the capsaicin 8% patch was noninferior to pregabalin in overall peripheral NP relief. In this study, we report the comparison of the two treatments in relieving DMA.

Methods

In a randomized, open‐label, head‐to‐head, 8‐week study, 488 patients with peripheral NP were treated with the capsaicin 8% patch (one application) or an optimized dose of pregabalin. Assessments included the area and intensity of DMA, and the number of patients achieving complete resolution of DMA.

Results

At baseline, 253 patients in the capsaicin 8% patch group and 235 patients in the pregabalin group had DMA. From baseline to end of study, the change in DMA intensity was significantly in favour of the capsaicin 8% patch versus pregabalin [−0.63 (95% CI: −1.04, −0.23; p = 0.002)]. Similarly, the capsaicin 8% patch was superior to pregabalin in reducing the area of DMA [−39.5 cm² (95% CI: −69.1, −10.0; p = 0.009)] from baseline to end of study. Overall, a greater proportion of patients had a complete resolution of allodynia with capsaicin 8% patch treatment compared with pregabalin treatment (24.1% vs. 12.3%; p = 0.001) at end of study.

Conclusion

Capsaicin 8% treatment was superior to pregabalin in reducing the intensity and area of DMA, and in the number of patients with complete resolution of DMA.

Significance

The superiority of a topical treatment over pregabalin in relieving DMA supports the view that both peripheral and central sensitization can mediate allodynia.

Alternatives to Opioids in the Pharmacologic Management of Chronic Pain Syndromes: A Narrative Review of Randomized, Controlled, and Blinded Clinical Trials

Chronic pain exerts a tremendous burden on individuals and societies. If one views chronic pain as a single disease entity, then it is the most common and costly medical condition. At present, medical professionals who treat patients in chronic pain are recommended to provide comprehensive and multidisciplinary treatments, which may include pharmacotherapy. Many providers use nonopioid medications to treat chronic pain; however, for some patients, opioid analgesics are the exclusive treatment of chronic pain. However, there is currently an epidemic of opioid use in the United States, and recent guidelines from the Centers for Disease Control (CDC) have recommended that the use of opioids for nonmalignant chronic pain be used only in certain circumstances. The goal of this review was to report the current body of evidence-based medicine gained from prospective, randomized-controlled, blinded studies on the use of nonopioid analgesics for the most common noncancer chronic pain conditions. A total of 9566 studies were obtained during literature searches, and 271 of these met inclusion for this review. Overall, while many nonopioid analgesics have been found to be effective in reducing pain for many chronic pain conditions, it is evident that the number of high-quality studies is lacking, and the effect sizes noted in many studies are not considered to be clinically significant despite statistical significance. More research is needed to determine effective and mechanism-based treatments for the chronic pain syndromes discussed in this review. Utilization of rigorous and homogeneous research methodology would likely allow for better consistency and reproducibility, which is of utmost importance in guiding evidence-based care.

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.

Endogenous analgesic effect of pregabalin: A double-blind and randomized controlled trial

BACKGROUND

Conditioned pain modulation (CPM) is widely used to measure endogenous analgesia, and a recent study indicated that drugs that act on endogenous analgesia are more effective in individuals with lower CPM. Recent animal studies have indicated that pregabalin activates endogenous analgesia by stimulating the descending pain inhibitory system. The present study examined whether the analgesic effect of pregabalin is greater in individuals with lower original endogenous analgesia using CPM.

METHODS

Fifty-nine healthy subjects were randomly assigned to either a pregabalin group or a placebo group, and 50 of them completed the study. CPM was measured before and after pregabalin or placebo administration. The correlation of initial CPM to change in CPM was compared between the pregabalin and placebo groups.

RESULTS

Initial CPM was significantly correlated with the change in CPM in the pregabalin group (r = -0.73, p < 0.0001) but not in the placebo group (p = 0.56) (difference in correlation coefficients between groups; p = 0.004). Furthermore, the initial CPM significantly affected the change in CPM in the pregabalin group but not in the placebo group (pregabalin group: adj R²  = 0.51, p < 0.001, y = -0.54x + 2.98; placebo group: p = 0.56, significant difference in regression slopes; p = 0.015). These results indicate that pregabalin has a higher endogenous analgesic effect in individuals with lower original endogenous analgesia.

SIGNIFICANCE

The analgesic effect of pregabalin depends on the original endogenous analgesia status. Its effect on conditioned pain modulation (CPM) was stronger for subjects with lower original endogenous analgesia, suggesting that the mechanism of pregabalin involves the improvement of endogenous analgesia.

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.

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.

Clinically relevant concentration of pregabalin has no acute inhibitory effect on excitation of dorsal horn neurons under normal or neuropathic pain conditions: An intracellular calcium-imaging study in spinal cord slices from adult rats

Pregabalin is thought to exert its therapeutic effect in neuropathic pain via binding to α2δ-1 subunits of voltage-gated calcium (Ca(2+)) channels. However, the exact analgesic mechanism after its binding to α2δ-1 subunits remains largely unknown. Whether a clinical concentration of pregabalin (≈10μM) can cause acute inhibition of dorsal horn neurons in the spinal cord is controversial. To address this issue, we undertook intracellular Ca(2+)-imaging studies using spinal cord slices with an intact attached L5 dorsal root, and examined if pregabalin acutely inhibits the primary afferent stimulation-evoked excitation of dorsal horn neurons in normal rats and in rats with streptozotocin-induced painful diabetic neuropathy. Under normal conditions, stimulation of a dorsal root evoked Ca(2+) signals predominantly in the superficial dorsal horn. Clinically relevant (10μM) and a very high concentration of pregabalin (100μM) did not affect the intensity or spread of dorsal root stimulation-evoked Ca(2+) signals, whereas an extremely high dose of pregabalin (300μM) slightly but significantly attenuated Ca(2+) signals in normal rats and in diabetic neuropathic (DN) rats. There was no difference between normal rats and DN rats with regard to the extent of signal attenuation at all concentrations tested. These results suggest that the activity of dorsal horn neurons in the spinal cord is not inhibited acutely by clinical doses of pregabalin under normal or DN conditions. It is very unlikely that an acute inhibitory action in the dorsal horn is the main analgesic mechanism of pregabalin in neuropathic pain states.

Road map for pain management in pancreatic cancer: A review

Beside its poor prognosis and its late diagnosis, pancreatic cancer remains one of the most painful malignancies. Optimal management of pain in this cancer represents a real challenge for the oncologist whose objective is to ensure a better quality of life to his patients. We aimed in this paper to review all the treatment modalities incriminated in the management of pain in pancreatic cancer going from painkillers, chemotherapy, radiation therapy and interventional techniques to agents under investigation and alternative medicine. Although specific guidelines and recommendations for pain management in pancreatic cancer are still absent, we present all the possible pain treatments, with a progression from medical multimodal treatment to radiotherapy and chemotherapy then interventional techniques in case of resistance. In addition, alternative methods such as acupuncture and hypnosis can be added at any stage and seems to contribute to pain relief.

The influence of thiamin on the efficacy of pregabalin in rats with spinal nerve ligation (SNL)-induced neuropathic pain

OBJECTIVE

The thiamin is often used in the treatment of neuropathy, and pregabalin is often used to treat neuropathic pain. Our study examined the influence of thiamin on the efficacy of pregabalin in a rat model of spinal nerve ligation (SNL)-induced neuropathic pain.

METHODS

Sprague-Dawley male rats were randomly divided into six groups. The neuropathic pain-relieving properties were measured by plantar test, cold plate test, and hot plate test after administration of pregabalin (i.v) and/or thiamin (i.p) in SNL rats 14 days after operation.

RESULTS

In the therapy period, pregabalin, or thiamin alone all produced antinociceptive effects in rats with neuropathic pain. And combination treatment of thiamin and pregabalin resulted in an enhanced pain relief compared to the administration of pregabalin or thiamin alone.

CONCLUSION

Combination of thiamin and pregabalin produces an additive antinociceptive effect in neuropathic pain rats, this drug combination may offer a beneficial treatment option for neuropathic pain.

Desmoid Tumors: A Review of the Literature and Pharmacologic Management

Desmoid tumors represent a nonmalignant proliferation of fibroblast-related cells. These rare tumors are difficult to treat and often persist as indolent, lifelong conditions. There are a number of treatments available for both anatomic and symptom regression. Some of these treatments, unfortunately, may not provide long-lasting results and may result in further complications. Pain is a distressing symptom that may be due to the tumor itself or the result of utilized treatments. Pharmacologic therapies represent a noninvasive alternative to surgical resection. Pain symptoms require therapeutic regimens that must be modified as the tumor evolves in expression. The individualized pain treatment program utilized may often reflect principles used in both nonmalignant and malignant pain management models. This review seeks to increase awareness of desmoid tumors through a review of the literature and discussion of its pharmacotherapeutic management.

Abuse Potential of Pregabalin: A Systematic Review

BACKGROUND

Several case reports and epidemiological studies have raised concern about the abuse potential of pregabalin, the use of which has increased substantially over the last decade. Pregabalin is, in some cases, used for recreational purposes and it has incurred attention among drug abusers for causing euphoric and dissociative effects when taken in doses exceeding normal therapeutic dosages or used by alternative routes of administration, such as nasal insufflation or venous injection. The magnitude of the abuse potential and the mechanism behind it are not fully known.

OBJECTIVE

The aim of this study was to present a systematic review of the data concerning the abuse potential of pregabalin.

METHODS

We performed a systematic literature search and reviewed the preclinical, clinical and epidemiological data on the abuse potential of pregabalin.

RESULTS

We included preclinical (n = 17), clinical (n = 19) and epidemiological (n = 13) studies addressing the abuse potential of pregabalin. We also reviewed case reports (n = 9) concerning abuse of pregabalin. The preclinical studies indicated that pregabalin possesses modulatory effects on the GABA and glutamate systems, leaving room for an abuse potential. Further, clinical studies reported euphoria as a frequent side effect in patients treated with pregabalin. The majority of case reports concerning abuse of pregabalin involved patients with a history of substance abuse and, similarly, epidemiological studies found evidence of abuse, especially among opiate abusers.

CONCLUSIONS

Overall, the available literature suggests an important clinical abuse potential of pregabalin and prescribers should pay attention to signs of abuse, especially in patients with a history of substance abuse.

A Randomized, Double-blind, Placebo-controlled Trial to Evaluate the Efficacy and Safety of Pregabalin for Postherpetic Neuralgia in a Population of Chinese Patients

BACKGROUND AND PURPOSE

Currently, there are limited options for treatment of postherpetic neuralgia (PHN) patients in China. While pregabalin is an effective treatment option for PHN in several countries, there is limited information on its efficacy in Chinese patients.

METHODS

This was an 8-week, double-blind, placebo-controlled trial in Chinese patients with PHN randomized (1:1) to pregabalin 300 mg/day or placebo. Primary efficacy endpoint was change from baseline in mean pain score (Daily Pain Rating Scale; 0 = 'no pain' to 10 = 'worst possible pain'). Secondary efficacy endpoints included change from baseline in overall pain intensity score, by visual analog scale (VAS; 0 = 'no pain' to 100 = 'worst possible pain') and daily sleep interference score (0 = 'pain does not interfere with sleep' to 10 = 'completely interferes').

RESULTS

A total of 220 patients were randomized and received treatment (111 pregabalin and 109 placebo). Improvement in mean pain score with pregabalin was significantly greater than placebo, least squares mean difference (95% CI), -0.71 (-1.08, -0.34); P = 0.0002. Improvements in VAS and sleep interference score at endpoint were significantly greater with pregabalin than placebo, least squares mean difference (95% CI), -8.18 (-11.99, -4.37); P < 0.0001, and -0.54 (-0.93, -0.14); P = 0.0079, respectively. Adverse events were consistent with current product labeling, with dizziness the most commonly reported adverse event (24.3% of pregabalin-treated patients).

CONCLUSION

Pregabalin improved measures of pain and sleep, and is well tolerated in Chinese patients with PHN. These results may inform physicians treating patients with PHN in China.

The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.

Intrathecal clonidine and adenosine: effects on pain and sensory processing in patients with chronic regional pain syndrome

Chronic pain may be accompanied by hyperalgesia and allodynia, and analgesic interventions may reduce these hypersensitivity phenomena. Preclinical data suggest that intrathecal clonidine and adenosine reduce hypersensitivity, but only clonidine reduces pain; therefore, we tested the effects of these interventions in patients with chronic pain. Twenty-two subjects with pain and hyperalgesia in a lower extremity from complex regional pain syndrome were recruited in a double-blind crossover study to receive intrathecal clonidine, 100 μg, or adenosine, 2 mg. Primary outcome measure was proportion with ≥30% reduction in pain 2 hours after injection, and secondary measures were pain report, areas of hypersensitivity, and temporal summation to heat stimuli. Treatments did not differ in the primary outcome measure (10 met success criterion after clonidine administration and 5 after adenosine administration), although they did differ in pain scores over time, with clonidine having a 3-fold greater effect (P = 0.014). Both drugs similarly reduced areas of hyperalgesia and allodynia by approximately 30% and also inhibited temporal summation. The percentage change in pain report did not correlate with the percentage change in areas of hyperalgesia (P = 0.09, r = 0.08) or allodynia (P = 0.24, r = 0.24) after drug treatment. Both intrathecal clonidine and adenosine acutely inhibit experimentally induced and clinical hypersensitivity in patients with chronic regional pain syndrome. Although these drugs do not differ in analgesia by the primary outcome measure, their difference in effect on pain scores over time and lack of correlation between effect on pain and hypersensitivity suggest that analgesia does not parallel antihyperalgesia with these treatments.

Predictors of placebo response in peripheral neuropathic pain: insights from pregabalin clinical trials

Background

Greater understanding of factors associated with the high placebo-response rates noted in recent neuropathic pain trials may improve trial design. This study investigated placebo response and its predictors in pregabalin trials in patients with diabetic peripheral neuropathy (DPN) or postherpetic neuralgia.

Patients and methods

Individual patient data from 16 randomized, placebo-controlled, double-blind trials of pregabalin in 3,053 patients with DPN and 1,460 patients with postherpetic neuralgia were pooled (by condition and all together) in order to investigate the placebo response and its predictors. Univariate and multivariate analyses were performed across all 16 trials to identify predictors of change in pain score in patients. Trials with a >2-point mean reduction in pain score at endpoint with placebo were designated high placebo response and were compared with low placebo-response trials (those with a ≤2-point mean reduction) with respect to patient and study characteristics.

Results

Three high placebo-response studies were identified, with all in DPN patients and all conducted postapproval of pregabalin. Younger age, higher mean baseline pain score, longer study duration, higher ratio of patients on active treatment to placebo, and study conducted postapproval were all significantly associated with a higher placebo response (P<0.05). There was a trend towards an increased placebo response in all studies over time without any corresponding change in the response to pregabalin.

Conclusion

Consideration of the factors identified here as contributing to a higher placebo response could help improve the sensitivity and accuracy of clinical trials in patients with neuropathic pain.

A comprehensive drug safety evaluation of pregabalin in peripheral neuropathic pain

Pregabalin is a commonly used therapy currently recommended as first-line treatment for a number of neuropathic pain (NeP) conditions. Since licensure, a number of clinical trials of pregabalin in different NeP conditions have been completed from which additional data on safety and tolerability can be drawn. In this analysis, patient-level data from 31 randomized clinical trials of pregabalin in peripheral NeP sponsored by Pfizer were pooled and assessed for incidence of adverse events (AEs). Incidence by age, disease condition, and race, together with risk differences and time to onset and resolution of AEs, was assessed. In total, 7,510 patients were included: 4,884 on pregabalin (representing 805 patient-years treatment) and 2,626 on placebo. Pregabalin vs. placebo risk analysis identified 9 AEs with a risk difference, for which the lower limit of the 95% confidence interval (CI) was > 1%: dizziness (risk difference [95% CI]: (17.0 [15.4 to 18.6]), somnolence (10.8 [9.5 to 12.1]), peripheral edema (5.4 [4.3 to 6.4]), weight increase (4.7 [3.9 to 5.5]), dry mouth (2.9 [2.1 to 3.8]), constipation (2.3 [1.5 to 3.2]), blurred vision (2.2 [1.6 to 2.9]), balance disorder (2.0 [1.5 to 2.5]), and euphoric mood (1.6 [1.2 to 2.0]). The most common AEs, dizziness and somnolence, typically emerged within the first 1 to 2 weeks of treatment and resolved 1 to 2 weeks later, without resulting in cessation of treatment. The data from this review provide information, indicating which AEs may be expected in patients treated with pregabalin, and suggest that careful dose titration to the highest tolerable dose is the most appropriate approach in clinical practice.

Time to improvement of pain and sleep quality in clinical trials of pregabalin for the treatment of fibromyalgia

OBJECTIVE

To determine the time to immediate and sustained clinical improvement in pain and sleep quality with pregabalin in patients with fibromyalgia.

DESIGN

A post hoc analysis of four 8- to 14-week phase 2-3, placebo-controlled trials of fixed-dose pregabalin (150-600 mg/day) for fibromyalgia, comprising 12 pregabalin and four placebo treatment arms.

PATIENTS

A total of 2,747 patients with fibromyalgia, aged 18-82 years.

METHODS

Pain and sleep quality scores, recorded daily on 11-point numeric rating scales (NRSs), were analyzed to determine time to immediate improvement with pregabalin, defined as the first of ≥2 consecutive days when the mean NRS score was significantly lower for pregabalin vs placebo in those treatment arms with a significant improvement at endpoint, and time to sustained clinical improvement with pregabalin, defined as a ≥1-point reduction of the baseline NRS score of patient responders who had a ≥30% improvement on the pain NRS, sleep NRS, or Fibromyalgia Impact Questionnaire (FIQ) from baseline to endpoint, or who reported "much improved" or "very much improved" on the Patient Global Impression of Change (PGIC) at endpoint.

RESULTS

Significant improvements in pain and sleep quality scores at endpoint vs placebo were seen in 8/12 and 11/12 pregabalin treatment arms, respectively (P < 0.05). In these arms, time to immediate improvements in pain or sleep occurred by day 1 or 2. Time to sustained clinical improvement occurred significantly earlier in pain, sleep, PGIC, and FIQ responders (P < 0.02) with pregabalin vs placebo.

CONCLUSIONS

Both immediate and sustained clinical improvements in pain and sleep quality occurred faster with pregabalin vs placebo.

Allodynia and hyperalgesia in neuropathic pain: clinical manifestations and mechanisms

Allodynia (pain due to a stimulus that does not usually provoke pain) and hyperalgesia (increased pain from a stimulus that usually provokes pain) are prominent symptoms in patients with neuropathic pain. Both are seen in various peripheral neuropathies and central pain disorders, and affect 15-50% of patients with neuropathic pain. Allodynia and hyperalgesia are classified according to the sensory modality (touch, pressure, pinprick, cold, and heat) that is used to elicit the sensation. Peripheral sensitisation and maladaptive central changes contribute to the generation and maintenance of these reactions, with separate mechanisms in different subtypes of allodynia and hyperalgesia. Pain intensity and relief are important measures in clinical pain studies, but might be insufficient to capture the complexity of the pain experience. Better understanding of allodynia and hyperalgesia might provide clues to the underlying pathophysiology of neuropathic pain and, as such, they represent new or additional endpoints in pain trials.

Reporting of sample size calculations in analgesic clinical trials: ACTTION systematic review

Sample size calculations determine the number of participants required to have sufficiently high power to detect a given treatment effect. In this review, we examined the reporting quality of sample size calculations in 172 publications of double-blind randomized controlled trials of noninvasive pharmacologic or interventional (ie, invasive) pain treatments published in European Journal of Pain, Journal of Pain, and Pain from January 2006 through June 2013. Sixty-five percent of publications reported a sample size calculation but only 38% provided all elements required to replicate the calculated sample size. In publications reporting at least 1 element, 54% provided a justification for the treatment effect used to calculate sample size, and 24% of studies with continuous outcome variables justified the variability estimate. Publications of clinical pain condition trials reported a sample size calculation more frequently than experimental pain model trials (77% vs 33%, P < .001) but did not differ in the frequency of reporting all required elements. No significant differences in reporting of any or all elements were detected between publications of trials with industry and nonindustry sponsorship. Twenty-eight percent included a discrepancy between the reported number of planned and randomized participants. This study suggests that sample size calculation reporting in analgesic trial publications is usually incomplete. Investigators should provide detailed accounts of sample size calculations in publications of clinical trials of pain treatments, which is necessary for reporting transparency and communication of pre-trial design decisions.

PERSPECTIVE

In this systematic review of analgesic clinical trials, sample size calculations and the required elements (eg, treatment effect to be detected; power level) were incompletely reported. A lack of transparency regarding sample size calculations may raise questions about the appropriateness of the calculated sample size.

Factors predicting adverse events associated with pregabalin administered for neuropathic pain relief

BACKGROUND

Pregabalin administration is occasionally abandoned due to adverse events such as somnolence, dizziness, unsteadiness, weight gain and edema. However, the exact causes of these differences in adverse events associated with pregabalin have not been elucidated.

OBJECTIVE

To identify factors predicting adverse events associated with pregabalin administered for neuropathic pain.

METHODS

The present study was a retrospective analysis involving 208&nbsp;patients with neuropathic pain who had been treated with pregabalin in the pain clinic at the authors' hospital between July 2010 and September 2011. Variables were extracted from the clinical records for regression analysis of factors related to the occurrence of adverse events associated with pregabalin administration. Multivariate logistic regression analysis was used to examine the relationship between various predictive factors and the adverse events.

RESULTS

Predictive factors were: duration of therapy (OR 1.684&nbsp;[95%&nbsp;CI 1.179 to 2.406]; P=0.0042) for somnolence; nonsteroidal anti-inflammatory drugs (OR 0.132 [95% CI 0.030 to 0.578]; P=0.0072), age (OR 3.137 [95% CI 1.220 to 8.066]; P=0.0177) and maintenance dose (OR 0.437 [95% CI 0.217 to 0.880]; P=0.0205) for unsteadiness; serum creatinine (OR 6.439&nbsp;[95% CI 1.541 to 26.902]; P=0.0107) for body weight gain; and neurotropin (OR 8.538 [95% CI 1.159 to 62.901]; P=0.0353) and serum creatinine (OR 6.912 [95% CI 1.118 to 42.726]; P=0.0375) for edema.

CONCLUSIONS

The results of the present study indicate that care is warranted regarding long durations of therapy for somnolence, advanced age rather than dose-dependent adverse events for unsteadiness, elevated serum creatinine level for weight gain, and elevated serum creatinine level and combination use of neurotropin for edema. The safety of the combined use of pregabalin and nonsteroidal anti-inflammatory drugs were also suggested.

Twice daily versus once nightly dosing of pregabalin for fibromyalgia: a double-blind randomized clinical trial of efficacy and safety

OBJECTIVE

To compare the efficacy, discontinuation rates, and safety of once nightly versus twice daily dosing of pregabalin in a community-based trial.

METHODS

This multicenter, double-blind, 8-week randomized clinical trial compared the effects of 300-mg daily doses of pregabalin given either twice daily or once nightly for the treatment of fibromyalgia in 177 patients. The primary outcome was the comparison of end point mean pain scores derived from a daily diary.

RESULTS

Both twice daily (88 patients randomized) and once nightly (89 patients) pregabalin significantly reduced the average severity of pain experienced by patients (P < 0.001 for both). Treatment-emergent adverse events were reported by significantly more patients in the twice daily group than those in the once nightly group (P = 0.023). There were no significant differences between the groups for the frequencies of individual adverse events (P > 0.05 for all). There was no significant difference in adverse events or efficacy in patients taking both pregabalin and a selective serotonin and norepinephrine reuptake inhibitor or selective serotonin uptake inhibitor.

CONCLUSION

While a nightly dosing schedule of pregabalin has been used by clinicians hoping to improve treatment, this study showed no significant difference (either beneficial or detrimental) between either treatment option. While there was a decrease in total patient-reported adverse events in the once nightly arm, the lack of specificity in relation to a particular adverse event suggested no real difference in adverse events.

Pregabalin: latest safety evidence and clinical implications for the management of neuropathic pain

Used mainly for the management of neuropathic pain, pregabalin is a gabapentinoid or anticonvulsant that was initially developed as an antiepileptic agent. After more than a decade of experience with pregabalin, experience and studies have shown that the adverse effect profile of pregabalin is well tolerated for the management of neuropathic pain and other conditions. Its use is associated with benign central nervous system and systemic adverse effects, and there are very limited metabolic, idiosyncratic or known teratogenic adverse effects. Along with its efficacy in particular neuropathic pain conditions, pregabalin's safety led it to be one of the first pharmacotherapies considered for the management of neuropathic pain. This review discusses the use of pregabalin as well as its potential adverse effects, including the most commonly noted features of sedation, dizziness, peripheral edema and dry mouth. Although other adverse effects may occur, these appear to be uncommon. The review also discusses the clinical implications of pregabalin's use for the clinician.

Pregabalin and Radicular Pain Study (PARPS) for Cervical Spondylosis in a Multiracial Asian Population

BACKGROUND

Pain from cervical spondylosis (CS) may result from degenerative spinal canal stenosis (cervical spondylotic myelopathy (CSM)) or lateral recesses compromise, leading to nerve root compression (cervical spondylotic radiculopathy (CSR)). Pregabalin was shown to be effective in randomized, placebo-controlled trials for post-herpetic neuralgia and diabetic neuropathy. We evaluate its efficacy in CS with underlying CSR or CSM in a prospective study comprising Asian patients for the first time.

METHODS

Patients with CS and CSR or CSM (clinical, MRI, or electrophysiological evidence) presenting with neuropathic pain were recruited. We excluded patients with diabetes, underlying neurological disease or who were previously on antiepileptics. Pregabalin 75 mg bd was administered for 4 weeks, after which dosage was increased to 150 mg bd for another 4 weeks if the visual analog scale (VAS) was not reduced by 50%. In addition, we monitored the short form McGill pain questionnaire (SFMPQ) at baseline, 4 weeks and 8 weeks. Mood changes were monitored using the hospital anxiety and depression score (HADS) with an identical timeline.

RESULTS

We recruited 50 patients, of which 23 completed the trial. Of the 27 who withdrew, 12 (44%) were for somnolence. Thirteen patients' (54%) dosages remained at 75 mg and 11 patients' (46%) dosages were escalated to 150 mg bd. There were significantly reducing trends from baseline for VAS (ANOVA, F(1, 21) = 25.4, P < 0.0005), SFMPQ (sensory) (F(1, 22) = 11.2, P = 0.003), and SFMPQ (affective) (F(1, 21) = 10.9, P = 0.008). For VAS, there was significant reduction at 4 weeks (P = 0.001) and 8 weeks (P < 0.0005) compared to baseline. For SFMPQ (sensory), there was significant reduction at 4 weeks (P = 0.01) and 8 weeks (P = 0.006) in scores compared to baselines. For SFMPQ (affective), there was significant reduction at 4 weeks (P = 0.04) and 8 weeks (P = 0.008) in scores compared to baseline. No significant anxiety (F(1, 4) = 1.3, P = 0.32) or depression (F(1, 4) = 0.06, P = 0.82) changes were observed in the HADS.

CONCLUSION

Pregabalin is efficacious in alleviation of pain symptoms related to CSR as a first-line single agent, evaluated by quantitative severity and other experiential scales. No significant mood changes reported in other studies were demonstrated. Somnolence was commonest adverse effect leading to high dropout rates, occurring early even at the lowest dose. The findings suggest the need for further studies of efficacy at lower dosages, particularly in the Asian population.

Therapeutic options for the treatment of postherpetic neuralgia: a systematic review

Postherpetic neuralgia (PHN) is a chronic and painful condition that may result in significant disturbances to normal activities and decreases in the quality of life for those affected. Despite the availability of several first- and second-line treatment options, many patients may experience refractory pain. The objectives of this review were to summarize evidence for Food and Drug Administration (FDA)-approved and off-label therapies for the treatment of PHN and to present gaps in the current literature for future research focus. Several agents, including pregabalin, gabapentin, and opioids, have been shown to significantly improve pain when compared with placebo. However, evidence regarding the comparative effectiveness of these treatment alternatives is lacking. In order to choose the optimal treatment, providers should consider issues related to efficacy, safety, and tolerability in conjunction with patient goals, preferences, and adherence issues. Evidence from randomized or observational studies that directly compare agents with each other should help to inform treatment choices.