New developments in the treatment algorithm for peripheral neuropathic pain

Modeling an evaluation of the efficacy of the novel neuroanalgesic drug mirogabalin for diabetic peripheral neuropathic pain and postherpetic neuralgia therapy

Diabetic peripheral neuropathic pain (DPNP) and postherpetic neuralgia (PHN) are challenging and often intractable complex medical conditions, with a substantial impact on the quality of life. Mirogabalin, a novel voltage-gated Ca2+ channel α2δ ligand, was approved for the indication of DPNP and PHN. However, the time course of effects has not yet been clarified.We aimed to establish pharmacodynamic and placebo effect models of mirogabalin and pregabalin in DPNP and PHN, and to quantitatively compare the efficacy characteristics (maximum efficacy, onset time, and other pharmacodynamic parameters) and safety of mirogabalin and pregabalin. Public databases were comprehensively searched for randomized placebo-controlled clinical trials. A model-based meta-analysis (MBMA) was developed to describe the time course of drug efficacy and placebo effects. Adverse events were compared using a fixed-effects meta-analysis. Sixteen studies including 5,147 participants were eligible for this study. The placebo effect was relatively high and gradually increased with time, and it required at least eight weeks to reach a plateau. The pharmacodynamic model revealed that the maximum pure efficacy for mirogabalin and pregabalin was approximately -7.85 % and -8.86 %, respectively; the efficacy of mirogabalin to relieve DPNP and PHN was not superior to that of pregabalin, and both drugs had similar safety. While the rate constant of the onset rate of pregabalin was approximately thrice as high as that of mirogabalin. In addition, the baseline level of pain was an important factor affecting pregabalin efficacy. These findings are helpful in evaluating the clinical extension value of mirogabalin. They suggest that the high placebo effect and the baseline level of pain should be considered when grouping patients in future research and development of voltage-gated Ca2+ channel neuroanalgesic.

Development of Capsaicin-Containing Analgesic Silicone-Based Transdermal Patches

Transdermal therapeutic systems (TTSs) enable convenient dosing in drug therapy. Modified silicone-polymer-based patches are well-controlled and cost-effective matrix diffusion systems. In the present study, we investigated the substance release properties, skin penetration, and analgesic effect of this type of TTS loaded with low-dose capsaicin. Release properties were measured in Franz diffusion cell and continuous flow-through cell approaches. Capsaicin was detected with HPLC-UV and UV spectrophotometry. Raman spectroscopy was conducted on human skin samples exposed to the TTS. A surgical incision or carrageenan injection was performed on one hind paw of male Wistar rats. TTSs were applied to the epilated dorsal skin. Patches were kept on the animals for 6 h. The thermal hyperalgesia and mechanical pain threshold of the hind paws were detected. Patches exhibited controlled, zero-order kinetic capsaicin release. According to the Raman mapping, capsaicin penetrated into the epidermis and dermis of human skin, where the target receptors are expressed. The thermal pain threshold drop of the operated rat paws was reversed by capsaicin treatment compared to that of animals treated with control patches. It was concluded that our modified silicone-polymer-based capsaicin-containing TTS is suitable for the relief of traumatic and inflammatory pain.

A large-scale database study for the prescription status of a new voltage-gated Ca2+ channel α2δ ligand, mirogabalin, in Japan

BACKGROUND

A new voltage-gated Ca²⁺ channel α₂δ ligand, mirogabalin, was first approved for treating peripheral neuropathic pain in Japan in 2019. This is the first report on the prescription status of mirogabalin using a large-scale prescription database.

RESEARCH DESIGN AND METHODS

The authors analyzed the prescription data of 12,924 patients prescribed mirogabalin between 1 June and 31 August 2020. The endpoints were the number of patients prescribed, prescription days, prescription doses, dose changes, co-prescription patterns, medication possession ratio (MPR), and treatment discontinuation rates (TDRs).

RESULTS

Mirogabalin was newly prescribed to 7,914 patients in the 3-month study period. Most patients were prescribed mirogabalin at about 10 mg/day during the study period, and 30.9% of patients were prescribed ≥ 20 mg/day on Day 90 after the first prescription. The most frequently prescribed concomitant drug was celecoxib. The MPR (80 to 110%) was 86.2%, indicating good treatment adherence. The cumulative TDRs during ≤ 7 Days, Days 31-60, and 61-90 were 14.0%, 70.0%, and 77.9%, respectively.

CONCLUSIONS

Mirogabalin was prescribed to a considerable number of patients. These results may be useful for optimizing mirogabalin use for patients with peripheral neuropathic pain in daily clinical practice.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000042592.

A review of a new voltage-gated Ca2+ channel α2δ ligand, mirogabalin, for the treatment of peripheral neuropathic pain

INTRODUCTION

Neuropathic pain (NeP) is a chronic and refractory condition in many patients, and its treatment is a challenge for physicians. A new voltage-gated Ca²⁺ channel α₂δ ligand, mirogabalin, has a high specific binding affinity for the α₂δ subunit, with a slower dissociation rate for α₂δ-1 than α₂δ-2 compared to that of pregabalin. Mirogabalin was shown to be effective in NeP animal models, with a margin of safety between central nervous system side effects and the analgesic effect of the dose. It exerted a favorable analgesic effect, was well tolerated in patients with peripheral NeP (P-NeP), and was first approved in Japan in 2019 and subsequently in Korea and Taiwan in 2020.

AREAS COVERED

The purpose of this article is to review the pharmacological characteristics, pharmacokinetics, and efficacy and safety of mirogabalin for NeP based on the results of non-clinical and clinical studies.

EXPERT OPINION

Although there are several first-line therapies for NeP, insufficient efficacy and adverse drug reactions of NeP drugs often cause patient dissatisfaction. Mirogabalin was effective and well tolerated with a step-wise dose increase in clinical studies on P-NeP patients. Thus, mirogabalin is expected to be a useful treatment option for patients with P-NeP.

Neuropathic Orofacial Pain

Neuropathic pain of the orofacial region can cause much distress in individuals presenting with this condition. It may be easily mistaken for dental pain, and hence many individuals may undergo unnecessary dental work. Knowledge of the types of neuropathic orofacial pain may assist in timely diagnosis and improvement of a patient's quality of life.

The 5% Lidocaine-Medicated Plaster: Its Inclusion in International Treatment Guidelines for Treating Localized Neuropathic Pain, and Clinical Evidence Supporting its Use

When peripheral neuropathic pain affects a specific, clearly demarcated area of the body, it may be described as localized neuropathic pain (LNP). Examples include postherpetic neuralgia and painful diabetic neuropathy, as well as post-surgical and post-traumatic pain. These conditions may respond to topical treatment, i.e., pharmaceutical agents acting locally on the peripheral nervous system, and the topical route offers advantages over systemic administration. Notably, only a small fraction of the dose reaches the systemic circulation, thereby reducing the risk of systemic adverse effects, drug–drug interactions and overdose. From the patient’s perspective, the analgesic agent is easily applied to the most painful area(s). The 5% lidocaine-medicated plaster has been used for several years to treat LNP and is registered in approximately 50 countries. Many clinical guidelines recommend this treatment modality as a first-line option for treating LNP, particularly in frail and/or elderly patients and those receiving multiple medications, because the benefit-to-risk ratios are far better than those of systemic analgesics. However, some guidelines make only a weak recommendation for its use. This paper considers the positioning of the 5% lidocaine-medicated plaster in international treatment guidelines and how they may be influenced by the specific criteria used in developing them, such as the methodology employed by randomized, placebo-controlled trials. It then examines the body of evidence supporting use of the plaster in some prevalent LNP conditions. Common themes that emerge from clinical studies are: (1) the excellent tolerability and safety of the plaster, which can increase patients’ adherence to treatment, (2) continued efficacy over long-term treatment, and (3) significant reduction in the size of the painful area. On this basis, it is felt that the 5% lidocaine-medicated plaster should be more strongly recommended for treating LNP, either as one component of a multimodal approach or as monotherapy.

The topical 5% lidocaine medicated plaster in localized neuropathic pain: a reappraisal of the clinical evidence

Topical 5% lidocaine medicated plasters represent a well-established first-line option for the treatment of peripheral localized neuropathic pain (LNP). This review provides an updated overview of the clinical evidence (randomized, controlled, and open-label clinical studies, real-life daily clinical practice, and case series). The 5% lidocaine medicated plaster effectively provides pain relief in postherpetic neuralgia, and data from a large open-label controlled study indicate that the 5% lidocaine medicated plaster is as effective as systemic pregabalin in postherpetic neuralgia and painful diabetic polyneuropathy but with an improved tolerability profile. Additionally, improved analgesia and fewer side effects were experienced by patients treated synchronously with the 5% lidocaine medicated plaster, further demonstrating the value of multimodal analgesia in LNP. The 5% lidocaine medicated plaster provides continued benefit after long-term (≤7 years) use and is also effective in various other LNP conditions. Minor application-site reactions are the most common adverse events associated with the 5% lidocaine medicated plaster; there is minimal risk of systemic adverse events and drug–drug interactions. Although further well-controlled studies are warranted, the 5% lidocaine medicated plaster is efficacious and safe in LNP and may have particular clinical benefit in elderly and/or medically compromised patients because of the low incidence of adverse events.

Multivariate proteomic analysis of the cerebrospinal fluid of patients with peripheral neuropathic pain and healthy controls - a hypothesis-generating pilot study

Pain medicine lacks objective biomarkers to guide diagnosis and treatment. Combining two-dimensional gel proteomics with multivariate data analysis by projection, we exploratively analyzed the cerebrospinal fluid of eleven patients with severe peripheral neuropathic pain due to trauma and/or surgery refractory to conventional treatment and eleven healthy controls. Using orthogonal partial least squares discriminant analysis, we identified a panel of 36 proteins highly discriminating between the two groups. Due to a possible confounding effect of age, a new model with age as outcome variable was computed for patients (n=11), and four out of 36 protein spots were excluded due to a probable influence of age. Of the 32 remaining proteins, the following seven had the highest discriminatory power between the two groups: an isoform of angiotensinogen (upregulated in patients), two isoforms of alpha-1-antitrypsin (downregulated in patients), three isoforms of haptoglobin (upregulated in patients), and one isoform of pigment epithelium-derived factor (downregulated in patients). It has recently been hypothesized that the renin–angiotensin system may play a role in the pathophysiology of neuropathic pain, and a clinical trial of an angiotensin II receptor antagonist was recently published. It is noteworthy that when searching for neuropathic pain biomarkers with a purely explorative methodology, it was indeed a renin–angiotensin system protein that had the highest discriminatory power between patients and controls in the present study. The results from this hypothesis-generating pilot study have to be confirmed in larger, hypothesis-driven studies with age-matched controls, but the present study illustrates the fruitfulness of combining proteomics with multivariate data analysis in hypothesis-generating pain biomarker studies in humans.

First-In-Human, Double-Blind, Placebo-Controlled, Randomized, Dose-Escalation Study of BG00010, a Glial Cell Line-Derived Neurotrophic Factor Family Member, in Subjects with Unilateral Sciatica

OBJECTIVE

To evaluate the safety, tolerability, and pharmacokinetics of single doses of BG00010 (neublastin, artemin, enovin) in subjects with unilateral sciatica.

METHODS

This was a single-center, blinded, placebo-controlled, randomized Phase 1 sequential-cohort, dose-escalation study (ClinicalTrials.gov identifier NCT00961766; funded by Biogen Idec). Adults with unilateral sciatica were enrolled at The Royal Adelaide Hospital, Australia. Four subjects were assigned to each of eleven cohorts (intravenous BG00010 0.3, 1, 3, 10, 25, 50, 100, 200, 400, or 800 μg/kg, or subcutaneous BG00010 50 μg/kg) and were randomized 3:1 to receive a single dose of BG00010 or placebo. The primary safety and tolerability assessments were: adverse events; clinical laboratory parameters and vital signs; pain as measured by a Likert rating scale; intra-epidermal nerve fiber density; and longitudinal assessment of quantitative sensory test parameters. Blood, serum, and plasma samples were collected for pharmacokinetic and pharmacodynamic assessments. Subjects were blinded to treatment assignment throughout the study. The investigator was blinded to treatment assignment until the Data Safety Review Committee review of unblinded data, which occurred after day 28.

RESULTS

Beyond the planned enrollment of 44 subjects, four additional subjects were enrolled into to the intravenous BG00010 200 μg/kg cohort after one original subject experienced mild generalized pruritus. Therefore, a total of 48 subjects were enrolled between August 2009 and December 2011; all were included in the safety analyses. BG00010 was generally well tolerated: in primary analyses, the most common treatment-emergent adverse events were changes in temperature perception, pruritus, rash, or headache; no trends were observed in clinical laboratory parameters, vital signs, intra-epidermal nerve fiber density, or quantitative sensory testing. BG00010 was not associated with any clear, dose-dependent trends in Likert pain scores. BG00010 was rapidly distributed, with a prolonged terminal elimination phase.

CONCLUSIONS

These data support the development of BG00010 for the treatment of neuropathic pain.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00961766.

Chronic abdominal syndrome due to nervous compression. Study of 100 cases and proposed diagnostic-therapeutic algorithm

OBJECTIVE

In the medical literature, thoracic disc protrusion has traditionally been considered a rare occurrence. We hypothesise that the incidence of such protrusions and their abdominal symptoms is higher than is generally believed and that their presence may account for a significant proportion of chronic non-visceral abdominal pains. Accordingly, the present study was designed to identify and quantify the symptoms experienced by patients with thoracic disc protrusion and to assess the relative risk of these symptoms being presented, compared to the general population.

DESIGN

We conducted a cross-sectional study with a control group. The following comparison groups were analysed: case group, consisting of 100 patients diagnosed with thoracic disc protrusion in our hospital between February 2007 and October 2012, and control group consisting of 100 subjects from the general population, chosen at random. To compare the symptoms observed in each group, the following tests were applied to all study subjects: clinical examination, gastrointestinal-related quality of life (GIQLI) questionnaire and DN4 questionnaire. We also reviewed the subjects' medical records for the previous 3 years.

RESULTS

The subjects in the case group had a significantly higher incidence of digestive-urologic symptoms, a poorer gastrointestinal quality of life and greater need of medical care than those in the control group. The differences were statistically significant for all the parameters studied. Almost all the case group subjects suffered chronic abdominal pain and/or digestive-urologic symptoms. We term this group of symptoms "chronic abdominal syndrome due to nervous compression". Nevertheless, in most cases, no neurologic aetiology was suspected, and therefore the treatment given was ineffective. In view of the results obtained, we propose a diagnostic-therapeutic algorithm for such patients.

CONCLUSION

Thoracic disc protrusion, as well as having a non-negligible incidence, is often associated with a digestive-urologic clinical syndrome, and this factor should be taken into account in all cases of chronic abdominal pain and other digestive-urologic symptoms when standard tests are negative, so that appropriate treatment may be given.

Analgesic topical capsaicinoid therapy increases somatostatin-like immunoreactivity in the human plasma

The aim of the present study was to evaluate the therapeutic potential of local capsaicinoid (EMSPOMA(®) cream) treatment on chronic low back pain in patients with degenerative spine diseases and to investigate the possible mechanism of action of the therapy. The qualitative and quantitative analyses of capsaicinoids in EMSPOMA(®) cream were performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the clinical study 20 patients with degenerative spine diseases were involved in a self-controlled examination. During the 21 day therapy they received 30 min daily treatment with capsaicinoid (EMSPOMA(®)) cream to the lumbar region of the back. The pain (VASs, Oswestry Disability Index) and the mobility of the lumbar region of the spine (Schober's, Domján's L and R test) were detected at baseline and at the end of the 1st, 2nd and 3rd weeks. The plasma level of somatostatin-like immunoreactivity (SST-LI) was measured by radioimmunoassay (RIA) before and after the treatment on the first and the last day of the therapy. Nonivamide (0.01%) was identified as the only capsaicinoid molecule in the cream. In the clinical study the 21 day local nonivamide treatment reduced the pain sensation. Oswestry Disability Index decreased from 39 ± 3.9% to 32.5 ± 4.4%. VASs showed 37.29%-59.51% improvement. In the plasma level of SST-LI threefold elevation was observed after the first nonivamide treatment. We conclude that nonivamide treatment exerts analgesic action in chronic low back pain and causes the release of the antinociceptive and anti-inflammatory neuropeptide somatostatin which may play pivotal role in the pain-relieving effect.

Glossopharyngeal neuralgia

In this review, the clinical characteristics, differentiating features from other forms of neuralgia, etiology and treatment options of glossopharyngeal neuralgia will be discussed.

Axonal voltage-gated ion channels as pharmacological targets for pain

Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage-gated K(+) channels and blockers of hyperpolarization-activated cyclic nucleotide-gated channels that were found to reduce neuronal activity were also found to be effective in neuropathic and inflammatory pain states. The isoforms of these channels present on nociceptive axons have limited specificity. The rationale for considering axonal voltage-gated ion channels as targets for pain treatment comes from the accumulating evidence that chronic pain states are associated with a dysregulation of these channels that could alter their specificity and make them more susceptible to pharmacological modulation. This drives the need for further development of subtype-specific voltage-gated ion channels modulators, as well as clinically available neurophysiological techniques for monitoring axonal ion channel function in peripheral nerves.

Effects of a Short Course of Oral Prednisolone in Patients with Bladder Pain Syndrome with Fluctuating, Worsening Pain despite Low-Dose Triple Therapy

PURPOSE

Triple therapy with gabapentin, amitriptyline, and nonsteroidal antiinflammatory drugs is efficacious for chronic bladder pain syndrome/interstitial cystitis (BPS/IC). However, transient, fluctuating, worsening pain or flare-up symptoms may develop during treatment for a variety of reasons. Here, we assessed the validity of our observational experience regarding a short course of oral prednisolone therapy, which might be of value in the management of flare-up symptoms of BPS/IC.

METHODS

Between May 2007 and May 2012, 7 women (mean age, 61.5 years; range, 44.8 to 75.4 years) with BPS/IC presenting with transient, fluctuating, worsening pain as a flare-up symptom despite low-dose triple therapy received a 1- to 3-month course of oral prednisolone 10 mg. The outcome measures used were the IC symptom scale (ICSS, O'Leary-Sant Interstitial Cystitis Symptom Index) and a visual analogue scale (VAS), which were completed at baseline and after treatment.

RESULTS

There were statistically significant differences in the ICSS and VAS score before and after prednisolone treatment (P<0.05 by Wilcoxon singed-rank test). The pretreatment IC symptom index (ICSI), IC problem index (ICPI), and VAS score were 16.7± 2.2, 13.7±2.3, and 8.3±1.5 (mean±standard deviation [SD]), and the posttreatment scores were 4.9±2.3, 4.3±1.1, and 2.5±0.9 (mean±SD), respectively. The ICSI, ICPI, and VAS scores were improved after prednisolone treatment by 70.7%, 68.6%, and 69.9%, respectively. Low-dose triple therapy with prednisolone caused no significant adverse effects.

CONCLUSIONS

In patients with BPS/IC who show transient, fluctuating, worsening pain as flare-up symptoms despite undergoing low-dose triple therapy, a short course of oral prednisolone therapy was sufficiently effective. However, large-scale studies should be performed to verify our findings.

Analgesic efficacy and safety of medical therapy alone vs combined medical therapy and extraoral glossopharyngeal nerve block in glossopharyngeal neuralgia

OBJECTIVE

The aim of this study is to compare medical therapy alone and medical therapy with add on extraoral glossopharyngeal nerve block in terms of analgesic efficacy and hemodynamic safety in patients with glossopharyngeal neuralgia (GPN). As GPN is a rare disease, our secondary targets were to review the demographic profile of the disease, clinical profile, and any associations with the disease.

DESIGN

This was a randomized, prospective, active-controlled, parallel group study conducted from 2007 to 2009 to determine the safety and efficacy of extraoral glossopharyngeal nerve block in GPN and compare it with pharmacological intervention. After institutional ethics committee approval and patient's consent, GPN patients were randomly allocated into two groups. Group A (N = 15) received standard medical therapy (gabapentin 300 mg, tramadol 50 mg TDS, methylcobalamin 500 μgm PO) and group B (N = 15) patients received extraoral glossopharyngeal nerve block together with standard medical therapy. Patients were analyzed for analgesic outcome using numerical pain scale (NPS) and brief pain inventory (BPI) assessing both analgesic effect and degree of interference in quality of life (QOL) during 3-month follow-up. They were also evaluated for any significant hemodynamic alterations.

RESULTS

Over the follow-up of 90 days, the mean NPS in group A decreased from 6 ± 2 to 3 ± 2 and in group B from 5 ± 1 to 2 ± 2. From the mean NPS scores, it can be interpreted that both the modalities were effective clinically in treating GPN. However, NPS scores were statistically similar by the end of 90 days. Improvement from baseline in BPI measurement of QOL (mood, interpersonal relationship, and emotion) was earlier in group B (1, 2, and 1 months, respectively) compared with group A (2, 3, and 2 months, respectively). However, there were no significant hemodynamic adverse outcomes after administration of the block.

CONCLUSION

This study found that patients in both the groups had significantly lower pain intensities, improved pain relief, and reduced pain interference with QOL, which was especially evident on fourth visit (2 months) after the initiation of treatment regimen. Both were safe and well tolerated. The study advocates rational polypharmacy approach (oral and block) in difficult to treat painful conditions. Further controlled trials are warranted to further define the impact of such a combination therapy.

Comparison of the effects of pelargonic acid vanillylamide and capsaicin on human vanilloid receptors

Pelargonic acid vanillylamide is like capsaicin a natural capsaicinoid from chili peppers and commonly used in food additives to create a hot sensation, even in self-defense pepper sprays and as an alternative to capsaicin in medical products for topical treatment of pain. Although the chemical structures of both compounds are similar, preclinical data suggest that capsaicin is the more potent compound. We therefore performed voltage-clamp recordings using cells transfected with the human vanilloid receptor TRPV1 in order to assess the responses of pelargonic acid vanillylamide and capsaicin at the receptor level. We provide evidence that at the molecular target TRPV1, the concentration-response curves, kinetics of current activation, as well as inhibition by the competitive antagonist capsazepine were not significantly different between the two capsaicinoids. We suggest that the different effects of the two capsaicinoids observed in previous studies may rather be due to different physicochemical or pharmacokinetic properties than to different pharmacological profiles at the receptor level.

Sprouted innervation into uterine transplants contributes to the development of hyperalgesia in a rat model of endometriosis

Endometriosis is an enigmatic painful disorder whose pain symptoms remain difficult to alleviate in large part because the disorder is defined by extrauteral endometrial growths whose contribution to pain is poorly understood. A rat model (ENDO) involves autotransplanting on abdominal arteries uterine segments that grow into vascularized cysts that become innervated with sensory and sympathetic fibers. ENDO rats exhibit vaginal hyperalgesia. We used behavioral, physiological, and immunohistochemical methods to test the hypothesis that cyst innervation contributes to the development of this hyperalgesia after transplant. Rudimentary sensory and sympathetic innervation appeared in the cysts at two weeks, sprouted further and more densely into the cyst wall by four weeks, and matured by six weeks post-transplant. Sensory fibers became abnormally functionally active between two and three weeks post-transplant, remaining active thereafter. Vaginal hyperalgesia became significant between four and five weeks post-transplant, and stabilized after six to eight weeks. Removing cysts before they acquired functional innervation prevented vaginal hyperalgesia from developing, whereas sham cyst removal did not. Thus, abnormally-active innervation of ectopic growths occurs before hyperalgesia develops, supporting the hypothesis. These findings suggest that painful endometriosis can be classified as a mixed inflammatory/neuropathic pain condition, which opens new avenues for pain relief. The findings also have implications beyond endometriosis by suggesting that functionality of any transplanted tissue can be influenced by the innervation it acquires.

Accelerating the development of improved analgesic treatments: the ACTION public-private partnership

There has been considerable progress identifying pathophysiologic mechanisms of neuropathic pain, but analgesic medications with improved efficacy, safety, and tolerability still represent an unmet public health need. Numerous treatments examined in recent randomized clinical trials (RCTs) have failed to show efficacy for neuropathic pain, including treatments that had previously demonstrated efficacy. This suggests that at least some negative results reflect limited assay sensitivity of RCTs to distinguish efficacious treatments from placebo. Patient characteristics, clinical trial research designs and methods, outcome measures, approaches to data analysis, and statistical power may all play a role in accounting for difficulties in demonstrating the benefits of efficacious analgesic treatments vs placebo. The identification of specific clinical trial characteristics associated with assay sensitivity in existing data has the potential to provide an evidence-based approach to the design of analgesic clinical trials. The US Food and Drug Administration recently launched the Analgesic Clinical Trial Innovations, Opportunities, and Networks (ACTION) public-private partnership, which is designed to facilitate the discovery and development of analgesics with improved efficacy, safety, and tolerability for acute and chronic pain conditions. ACTION will establish a collaborative effort to prioritize research objectives, develop a standardized analgesic database platform, and conduct methodologically focused studies to increase the assay sensitivity and efficiency of analgesic clinical trials. The results of these activities have the potential to inform and accelerate the development of improved pain management interventions of all types, not just pharmacologic treatments.

Combination therapy with transdermal buprenorphine and pregabalin for chronic low back pain

SUMMARY 

AIM

The aim of this study was to evaluate the efficacy and safety of combined transdermal buprenorphine and pregabalin in chronic low back pain.

PATIENTS & METHODS

A total of 45 patients with chronic low back pain were recruited into the study. For an initial 3-week period, all patients received transdermal buprenorphine 35 µg/h. After 3 weeks of only transdermal buprenorphine 35 µg/h, patients were randomized (single-blind) to receive transdermal buprenorphine 35 µg/h plus pregabalin 300 mg/day (group A) or transdermal buprenorphine 35 µg/h plus placebo (group B), and were observed for a further 3-week period. Efficacy parameters were weekly mean Visual Analog Scale (VAS) scores, the Pain Rating Index (PRI) of the Short-Form McGill Pain Questionnaire (SF-MPQ), the Present Pain Index (PPI) of the SF-MPQ and sleep interference. We also evaluated the use of rescue medication (paracetamol [acetaminophen]) and the presence of adverse events.

RESULTS

A total of 44 patients were evaluated for efficacy and safety parameters. Pain relief, as assessed by VAS, PPI and PRI, improved significantly (p < 0.05) in all patients after the first week of treatment with only transdermal buprenorphine. Following randomization, only patients in group A showed further reductions in the mean VAS, PPI and PRI scores. Moreover, patients in group A had a lower consumption of rescue medication than those in group B. There was a low incidence of mild adverse events in both group A and group B, with no serious adverse events in either group.

CONCLUSION

Pregabalin 300 mg/day as an add-on to transdermal buprenorphine 35 µg/h led to significant pain reduction and a significant reduction of interference with sleep quality in patients with chronic low back pain.