Long-term safety of NGX-4010, a high-concentration capsaicin patch, in patients with peripheral neuropathic pain

Pharmacotherapy and noninvasive neurostimulation for neuropathic pain

Neuropathic pain poses a significant challenge due to its complex mechanisms, necessitating specific treatments. In recent decades, significant progress has been made in the clinical research of neuropathic pain, marking a shift from empirical strategies to evidence-based medicine in its management. This review outlines both pharmacological and non-pharmacological interventions. Antidepressants (tricyclic and serotonin-noradrenaline reuptake inhibitors), antiepileptics (gabapentin, pregabalin), and topical agents constitute the main pharmacological treatments. These approaches target peripheral or central mechanisms associated with neuropathic pain. Noninvasive neurostimulation, including transcutaneous electrical nerve stimulation (TENS) and repetitive transcranial magnetic stimulation (rTMS), provides non-pharmacological alternatives. However, challenges persist in effectively targeting existing medications and developing drugs that act on novel targets, necessitating innovative therapeutic strategies.

Is the Capsaicin 179 mg (8% w/w) Cutaneous Patch an Appropriate Treatment Option for Older Patients with Peripheral Neuropathic Pain?

Introduction

Capsaicin 179 mg (8% weight per weight) cutaneous patch ("capsaicin patch") is a recommended topical treatment for peripheral neuropathic pain (PNP). In older patients, topical treatments may be preferred over systemic treatments, but data specific to the older population are scarce.

Methods

We conducted pooled analyses of multiple clinical trials to evaluate efficacy and safety of capsaicin patch in older patients. The analysis of efficacy included four randomized, double-blind, 12-week studies with similar trial design comparing a single treatment of capsaicin 179 mg cutaneous patch vs low-dose control patch in post-herpetic neuralgia. For the safety evaluation, data were pooled from 18 interventional studies in which capsaicin patch was used in PNP with varying etiologies.

Results

Capsaicin patch had similar analgesic efficacy in elderly (n=582) and non-elderly patients (n=545) in terms of change from baseline to 2-12 weeks in the 11-point numeric pain rating scale (NPRS) score for average pain over the previous 24 hours. In both age groups, decrease in NPRS score was significantly greater with capsaicin patch vs control. Older patients treated with capsaicin patch were significantly more likely than those in the control group to achieve responder status (ie mean decrease in NPRS score from baseline to week 2-12 of at least 30% or ≥2 points): 36.1% vs 27.1% (odds ratio [OR] [95% CI] 1.52 [1.06, 2.18]; P=0.0231) and 33.1% vs 20.9% (OR [95% CI] 1.90 [1.30, 2.78]; P=0.0009) for active treatment vs control group, respectively. Similar proportions of non-elderly patients (n=2,311) and elderly patients (n=537) treated with capsaicin patch experienced treatment-emergent adverse events (TEAEs) (81.6% and 78.1%, respectively) and serious TEAEs (8.2% and 7.2%), with application-site reactions the most common TEAEs in both groups.

Conclusion

The capsaicin patch was equally efficacious and well tolerated in older patients as in younger patients.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Prescription Trends in Complex Regional Pain Syndrome: A Retrospective Case-Control Study

OBJECTIVE

The objective of this study was to evaluate discrepancies in prescription trends for analgesic medications in complex regional pain syndrome (CRPS) patients based on recommendations in the literature.

DESIGN

We conducted a retrospective case-control study.

SUBJECTS

A total of 2510 CRPS patients and 2510 demographic-matched controls participated in this study.

METHODS

The SlicerDicer feature in Epic was used to find patients diagnosed with CRPS I or II between January 2010 and November 2022. An equal number of age-, gender-, and race-matched controls without a CRPS diagnosis were retracted from Epic. General and CRPS-associated prescription frequencies for the following classes were retrieved for both cases and controls: benzodiazepines, bisphosphonates, calcitonin, capsaicin, neuropathic pain medications, NSAIDs, opioids, and steroids.

RESULTS

A total of 740 (29%) CRPS patients and 425 (17%) controls were prescribed benzodiazepines (95% CI 0.1-0.15), 154 (6.1%) CRPS patients and 52 (2.1%) controls were prescribed capsaicin (95% CI 0.03-0.05), 1837 (73%) CRPS patients and 927 (37%) controls were prescribed neuropathic pain medications (95% CI 0.05-0.34), 1769 (70%) CRPS patients and 1217 (48%) controls were prescribed opioids (95% CI 0.19-0.25), 1095 (44%) CRPS patients and 1217 (48%) controls were prescribed steroids (95% CI 0.08-0.14), and 1638 (65%) CRPS patients and 1765 (70%) controls were prescribed NSAIDs (95% CI -0.08-0.02), p < 0.001 for all classes. With CRPS-associated prescriptions, (95% CI 0.05-0.16, p < 0.001) more CRPS patients were prescribed opioids (N = 398, 59%) than controls (N = 327, 49%).

CONCLUSIONS

CRPS is difficult to treat with significant variance in suggested treatment modalities. Based on the results of our study, there is a divergence between some published recommendations and actual practice.

Complex Regional Pain Syndrome: Practical Diagnostic and Treatment Guidelines, 5th Edition

There have been some modest recent advancements in the research of Complex Regional Pain Syndrome, yet the amount and quality of the work in this complicated multifactorial disease remains low (with some notable exceptions; e.g., the recent work on the dorsal root ganglion stimulation). The semi-systematic (though in some cases narrative) approach to review is necessary so that we might treat our patients while waiting for "better research." This semi-systematic review was conducted by experts in the field, (deliberately) some of whom are promising young researchers supplemented by the experience of "elder statesman" researchers, who all mention the system they have used to examine the literature. What we found is generally low- to medium-quality research with small numbers of subjects; however, there are some recent exceptions to this. The primary reason for this paucity of research is the fact that this is a rare disease, and it is very difficult to acquire a sufficient sample size for statistical significance using traditional statistical approaches. Several larger trials have failed, probably due to using the broad general diagnostic criteria (the "Budapest" criteria) in a multifactorial/multi-mechanism disease. Responsive subsets can often be identified in these larger trials, but not sufficient to achieve statistically significant results in the general diagnostic grouping. This being the case the authors have necessarily included data from less compelling protocols, including trials such as case series and even in some instances case reports/empirical information. In the humanitarian spirit of treating our often desperate patients with this rare syndrome, without great evidence, we must take what data we can find (as in this work) and tailor a treatment regime for each patient.

The role of the capsaicin 8% patch in the treatment of painful diabetic peripheral neuropathy

Treatment of painful diabetic peripheral neuropathy (PDPN) is challenging and often limited by drug tolerability and adverse effects. This review article focuses on the high-dose (8%) capsaicin patch that allows for improved efficacy and reduced application frequency in comparison to low-dose capsaicin formulations. Systemic absorption is minimal resulting in fewer systemic side effects than first-line oral medications. There is evidence that capsaicin patch treatment is well-tolerated, safe and provides effective pain relief maintained for several weeks; well-powered studies are needed to confirm these findings. The capsaicin 8% patch may benefit patients at high risk for adverse effects from oral medication, polypharmacy or inadequate pain relief from first-line therapies.

Capsaicin 8% patch Qutenza and other current treatments for neuropathic pain in chemotherapy-induced peripheral neuropathy (CIPN)

PURPOSE OF REVIEW

Current oral treatments for neuropathic pain associated with chemotherapy-induced peripheral neuropathy (CIPN) have limited clinical efficacy, and undesirable side-effects. Topically delivered treatments have the advantage of avoiding CNS side-effects, while relieving pain. We have reviewed treatments of neuropathic pain associated with CIPN, focusing on the Capsaicin 8% patch, which can provide pain relief for up to 3 months or longer after a single 30-60-min application.

RECENT FINDINGS

Capsaicin 8% patch is a licensed treatment in the EU/UK for neuropathic pain and shown to be safe and effective in providing pain relief for patients with CIPN. Repeated daily oral or topical administrations are not required, as with other current treatments. The side-effects are transient and restricted to the time around patch application. New evidence suggests the Capsaicin 8% patch can promote the regeneration and restoration of skin nerve fibres in CIPN, in addition to the pain relief.

SUMMARY

The Capsaicin 8% patch is now often a preferred a treatment option for localised neuropathic pain conditions, including the feet and hands in patients with CIPN. Capsaicin 8% patch can be repeated three-monthly, if needed, for a year. In addition to pain relief, it may have a disease-modifying effect.

The efficacy and safety profile of capsaicin 8% patch versus 5% Lidocaine patch in patients with diabetic peripheral neuropathic pain: a randomized, placebo-controlled study of south Asian male patients

Aims

Diabetic peripheral neuropathy affects up to 60% of individuals and often leads to foot ulceration and eventual amputation. When oral therapy has failed to achieve pain relief, the first line local treatment is the 5% lidocaine-medicated plaster which provides local relief. Capsaicin 8% patch is considered a promising topical treatment for diabetic peripheral neuropathy. The present study investigated the efficacy, safety and tolerability of capsaicin 8% patch vs 5% lidocaine patch treatments over 24 weeks in South Asian male diabetic patients with established peripheral diabetic neuropathy.

Methods

Analgesic effectiveness was assessed by observing any change in the Numeric Pain Rating Scale (NPRS) score, Brief Pain Inventory (BPI) for painful diabetic peripheral neuropathy (BPI-DPN question 4) and Patient Global Impression of Change (PGIC). All patients received 4% lidocaine gel/cream for 60 min prior to patch application. The trial was probably underpowered, taking into account the smaller than expected number of participants from the calculated 350 sample size required for the whole study. Two hundred ninety-one individuals were divided into three groups based on treatment regimen; Group LL (Lidocaine + Lidocaine), Group LP (Lidocaine + Placebo), Group LC (Lidocaine + Capsaicin). The treatment procedure was conducted once initially and then repeated once at 12 weeks. The patients were followed up on alternate weeks till 24 weeks after the initial treatment.

Results

Group LC experienced a more significant reduction in the average pain intensity (p < 0.05) during the last twenty-four hours. Group LC showed more significant reduction of pain compared to control (p < 0.01), a baseline score of 5.4 ± 1.2 dropped to 3.2 ± 1.5 by week 24 of treatment. The change in mean daily pain intensity was - 2.2 ± 1.5 [95% CI: -2.45, -1.5]. Group LL and LC experienced a significant overall improvement (slightly, much or very much) in the health status during the study. After the second week of the treatment, patient satisfaction scores were 2.1 ± 1.1 in Group LL which increased to 3.2 ± 1.2 by week 24 of treatment. The capsaicin 8% patch appears to be reasonably well tolerated since there were no discontinuations because of serious drug-related treatment emergent adverse event (TEAEs).

Conclusions

The aim of the present study was to assess the efficacy, safety and tolerability of the 8% capsaicin patch in patients with established painful diabetic neuropathy. There was a sustained treatment response to the initial and repeat treatment of the capsaicin 8% patch over the 24 weeks. The study population was very specific so further studies are required to investigate the generalizability of the results for patients experiencing painful diabetic neuropathy. The patch could be considered as an effective long-term treatment option in individuals with painful diabetic neuropathy, particularly those experiencing inadequate pain relief or side effects from systemic therapies.

Bayesian-based withdrawal estimates using pharmacokinetic parameters for two capsaicinoid-containing products administered to horses

Capsaicinoids deter horses from chewing on bandages and are applied topically to provide analgesia to musculoskeletal injuries. They are banned during competition due to their nerve blocking properties. The pharmacokinetics of oral (PO) and direct gastric administration via nasogastric tube (NG), or topical (TOP) administration of two capsaicinoid-containing products were investigated, and the withdrawal times required prior to competition were estimated. Capsaicin (CAP) and dihydrocapsaicin (DCAP) were quantified in plasma, and both compounds were best described by a delayed absorption two compartment elimination model following PO administration and by a first order absorption one compartment elimination model following TOP administration. Capsaicin and DCAP could not be quantified in most samples following NG administration. Following PO administration, the time to maximum plasma concentration (T_max ) for CAP and DCAP was 0.25 (0.08-0.50) hr. Following TOP application, the Tmax for CAP and DCAP was 4 (2-6) and 5 (3-12) hr, respectively. By 8 hr post-PO administration and 36 hr post-TOP application, CAP and DCAP were below the lower limit of quantification. Capsaicin and DCAP were not detected in urine samples. Withdrawal times were predicted using the 99.99% credibility interval limits of the pharmacokinetic parameters calculated with Bayesian estimation.

Fight fire with fire: Neurobiology of capsaicin-induced analgesia for chronic pain

Capsaicin, the pungent ingredient in chili peppers, produces intense burning pain in humans. Capsaicin selectively activates the transient receptor potential vanilloid 1 (TRPV1), which is enriched in nociceptive primary afferents, and underpins the mechanism for capsaicin-induced burning pain. Paradoxically, capsaicin has long been used as an analgesic. The development of topical patches and injectable formulations containing capsaicin has led to application in clinical settings to treat chronic pain conditions, such as neuropathic pain and the potential to treat osteoarthritis. More detailed determination of the neurobiological mechanisms of capsaicin-induced analgesia should provide the logical rationale for capsaicin therapy and help to overcome the treatment's limitations, which include individual differences in treatment outcome and procedural discomfort. Low concentrations of capsaicin induce short-term defunctionalization of nociceptor terminals. This phenomenon is reversible within hours and, hence, likely does not account for the clinical benefit. By contrast, high concentrations of capsaicin lead to long-term defunctionalization mediated by the ablation of TRPV1-expressing afferent terminals, resulting in long-lasting analgesia persisting for several months. Recent studies have shown that capsaicin-induced Ca²⁺/calpain-mediated ablation of axonal terminals is necessary to produce long-lasting analgesia in a mouse model of neuropathic pain. In combination with calpain, axonal mitochondrial dysfunction and microtubule disorganization may also contribute to the longer-term effects of capsaicin. The analgesic effects subside over time in association with the regeneration of the ablated afferent terminals. Further determination of the neurobiological mechanisms of capsaicin-induced analgesia should lead to more efficacious non-opioidergic analgesic options with fewer adverse side effects.

Capsaicin 8% dermal patch in clinical practice: an expert opinion

INTRODUCTION

Neuropathic pain (NP) is caused by a lesion or disease of the somatosensory system, which can severely impact patients' quality of life. The current-approved treatments for NP comprise of both centrally acting agents and topical drugs, including capsaicin 8% dermal patches, which is approved for the treatment of peripheral NP.

AREAS COVERED

The authors summarize literature data regarding capsaicin use in patients who suffer from NP and discuss the clinical applications of this topical approach.

EXPERT OPINION

Overall, the capsaicin 8% dermal patch is as effective in reducing pain intensity as other centrally active agents (i.e. pregabalin). Some studies have also reported fewer systemic side effects, a faster onset of action and superior treatment satisfaction compared with systemic agents. In our opinion, capsaicin 8% dermal patches also present additional advantages, such as a good systemic tolerability, the scarcity of adverse events, the possibility to combine it with other agents, and a good cost-effective profile. It is important to note that, as the mechanism of action of capsaicin 8% is the 'defunctionalization' of small afferent fibers through interaction with TRPV1 receptors, the peripheral expression of this receptor on nociceptor fibers, is crucial to predict patient's response to treatment.

Pharmacologic and Non-Pharmacologic Interventions for HIV-Neuropathy Pain. A Systematic Review and a Meta-Analysis

Background and Objectives: Among HIV infection symptoms, sensory neuropathy (HIV-SN) remains a main cause of suffering, with incidence varying from 13-50%. So far, numerous pharmacological and non-pharmacological treatments have been tested, although few evidence-based analgesic options are available. We conducted an up-to-date systematic review and meta-analysis of the literature in order to evaluate the efficacy and safety of pharmacologic and non-pharmacologic treatments for pain control, in patients with HIV neuropathy. Materials and Methods: We searched MEDLINE, EMBASE, Scopus/Elsevier, The Cochrane Central Register of Controlled Trials (CENTRAL), USA Clinical Trials registry, and The International Web of Science up to April 2019. All randomized controlled trials evaluating efficacy and safety of non-pharmacologic and pharmacologic therapies were included. Efficacy was defined as pain reduction during the study period. Safety was estimated from adverse events. A meta-analysis was performed whenever possible. Results: 27 randomized controlled trials (RCTs) were included for analysis (7 evaluating non pharmacologic interventions, 20 pharmacologic therapies). Non-pharmacologic studies (n = 742) involved seven different therapeutic modalities. Only Acupuncture/Moxibustion showed pain reduction over placebo, Gracely Pain Scale Mean (SD): Acu/Moxa 0.85 (0.12), placebo 1.10 (0.09), p = 0.05. Pharmacologic studies, involving 2516 patients revealed efficacy for capsaicin 8% over placebo (mean difference -8.04 [95% CI: -14.92 -1.15], smoked cannabis (where pooling data for meta-analysis was not possible) and recombinant Nerve Growth Factor. Conclusion: Despite various modalities for pain control in HIV-SN, strongest evidence exists for capsaicin 8% and smoked cannabis, although of low methodological quality. Among non-pharmacologic modalities, only Acu/Moxa gave a marginal beneficial effect in one study, possibly limited by inherent methodological flaws.

Capsaicin 8% Dermal Patch: A Review in Peripheral Neuropathic Pain

The adhesive capsaicin dermal patch (Qutenza^®) delivers a high concentration (8% w/w) of synthetic capsaicin, a highly selective agonist of transient receptor potential vanilloid-1 (TRPV-1), directly to the site of pain. The capsaicin 8% dermal patch is indicated in the EU for the treatment of peripheral neuropathic pain (PNP) in adults, either alone or in combination with other medicinal products for pain. In patients with painful diabetic peripheral neuropathy, a single 30-min application of the capsaicin 8% dermal patch provided 12 weeks of pain relief and improved sleep quality compared with placebo. Repeat treatment with the capsaicin 8% dermal patch plus standard of care over 52 weeks provided sustained pain relief, with no negative neurological effects compared with standard of care alone. The capsaicin 8% dermal patch was non-inferior to oral pregabalin in relieving pain in patients with non-diabetic PNP, with a faster onset of action and greater treatment satisfaction. A single 60-min application of the capsaicin 8% dermal patch provided rapid and sustained pain relief in patients with postherpetic neuralgia. Results in patients with HIV-associated neuropathy were equivocal, with a significant improvement in pain intensity observed in one trial, but not in the other. The capsaicin 8% dermal patch was generally well tolerated; transient application-site reactions were the most common adverse events. In conclusion, the capsaicin 8% dermal patch is a useful addition to the treatment options currently available for patients with PNP.

Rational treatment of chemotherapy-induced peripheral neuropathy with capsaicin 8% patch: from pain relief towards disease modification

Purpose

Chemotherapy-induced peripheral neuropathy (CIPN) with associated chronic pain is a common and disabling condition. Current treatments for neuropathic pain in CIPN are largely ineffective, with unfavorable side-effects. The capsaicin 8% patch (capsaicin 179 mg patch) is approved for the treatment of neuropathic pain: a single topical cutaneous application can produce effective pain relief for up to 12 weeks. We assessed the therapeutic potential of capsaicin 8% patch in patients with painful CIPN, and its mechanism of action.

Patients and methods

16 patients with chronic painful CIPN (mean duration 2.5 years), in remission for cancer and not receiving chemotherapy, were treated with 30 min application of capsaicin 8% patch to the feet. Symptoms were monitored using the 11-point numerical pain rating scale (NPRS), and questionnaires. Investigations were performed at baseline and three months after patch application, including skin biopsies with a range of markers, and quantitative sensory testing (QST).

Results

Patients reported significant reduction in spontaneous pain (mean NPRS: −1.27; 95% CI 0.2409 to 2.301; p=0.02), touch-evoked pain (−1.823; p=0.03) and cold-evoked pain (−1.456; p=0.03). Short-Form McGill questionnaire showed a reduction in neuropathic (p=0.0007), continuous (p=0.01) and overall pain (p=0.004); Patient Global Impression of Change showed improvement (p=0.001). Baseline skin biopsies showed loss of intra-epidermal nerve fibers (IENF), and also of sub-epidermal nerve fibers quantified by image analysis. Post-patch application skin biopsies showed a significant increase towards normalization of intra-epidermal and sub-epidermal nerve fibers (for IENF: structural marker PGP9.5, p=0.009; heat receptor TRPV1, p=0.027; regenerating nerve marker GAP43, p=0.04). Epidermal levels of Nerve Growth Factor (NGF), Neurotrophin-3 (NT-3), and Langerhans cells were also normalized. QST remained unchanged and there were no systemic side-effects, as in previous studies.

Conclusion

Capsaicin 8% patch provides significant pain relief in CIPN, and may lead to regeneration and restoration of sensory nerve fibers ie, disease modification.

QAPSA: post-marketing surveillance of capsaicin 8% patch for long-term use in patients with peripheral neuropathic pain in France

OBJECTIVE

To describe the characteristics of patients treated with the capsaicin 8% patch, prescribing conditions, long-term effects of repeat treatment on pain intensity and perception, quality of life, and impact on concomitant medication.

METHODS

A national, longitudinal, prospective, non-interventional, post-marketing open study was conducted in 50 French pain centers. Adult volunteer non-diabetic patients with peripheral neuropathic pain receiving capsaicin 8% patch treatment were consecutively enrolled. Treatment could be repeated over a 12-month period, with 6 months' follow-up after last application.

RESULTS

A total of 684 patients (age: 53.0 ± 14.9 years, mean ± standard deviation; post-traumatic/surgical peripheral neuropathic pain: 76.3%; pain intensity: 6.2 ± 1.7; pain duration: 3.0 years, median) were treated with 1 to 5 patches at 3/4 month intervals; 70.3% were naive to capsaicin 8% patch treatment at inclusion. Six months after last application, treatment was considered as successful for 21.8% (95% confidence interval: 17.5%-26.7%) of patients by a stringent criterion combining improvement according to the patient's global impression of change (PGIC) and at least 30% improvement on a numerical pain rating scale (NPRS). Clinically relevant improvement in health-related quality of life was observed at end-of-study. No unexpected safety concerns were observed with capsaicin 8% patch repeat treatment.

CONCLUSIONS

The data of this post-marketing study meets the request by the French authorities for additional data on conditions of use in everyday practice. They confirmed the tolerance and long-term effect of capsaicin 8% patch in patients with peripheral neuropathic pain in real-world conditions.

Capsaicin 8% patch treatment for amputation stump and phantom limb pain: a clinical and functional MRI study

Purpose

The aim of this study was to measure the efficacy of a single 60 min application of capsaicin 8% patch in reducing chronic amputation stump and phantom limb pain, associated hypersensitivity with quantitative sensory testing, and changes in brain cortical maps using functional MRI (fMRI) scans.

Methods

A capsaicin 8% patch (Qutenza) treatment study was conducted on 14 patients with single limb amputation, who reported pain intensity on the Numerical Pain Rating Scale ≥4/10 for chronic stump or phantom limb pain. Pain assessments, quantitative sensory testing, and fMRI (for the lip pursing task) were performed at baseline and 4 weeks after application of capsaicin 8% patch to the amputation stump. The shift into the hand representation area of the cerebral cortex with the lip pursing task has been correlated with phantom limb pain intensity in previous studies, and was the fMRI clinical model for cortical plasticity used in this study.

Results

The mean reduction in spontaneous amputation stump pain, phantom limb pain, and evoked stump pain were −1.007 (p=0.028), −1.414 (p=0.018), and −2.029 (p=0.007), respectively. The areas of brush allodynia and pinprick hypersensitivity in the amputation stump showed marked decreases: −165 cm², −80% (p=0.001) and −132 cm², −72% (p=0.001), respectively. fMRI analyses provided objective evidence of the restoration of the brain map, that is, reversal of the shift into the hand representation of the cerebral cortex with the lip pursing task (p<0.05).

Conclusion

The results show that capsaicin 8% patch treatment leads to significant reduction in chronic pain and, particularly, in the area of stump hypersensitivity, which may enable patients to wear prostheses, thereby improving mobility and rehabilitation. Phantom limb pain (“central” pain) and associated brain plasticity may be modulated by peripheral inputs, as they can be ameliorated by the peripherally restricted effect of the capsaicin 8% patch.

Feasibility of Topical Applications of Natural High-Concentration Capsaicinoid Solutions in Patients with Peripheral Neuropathic Pain: A Retrospective Analysis

Background. Capsaicin, one of several capsaicinoid compounds, is a potent TRPV1 agonist. Topical application at high concentration (high concentration, >1%) induces a reversible disappearance of epidermal free nerve endings and is used to treat peripheral neuropathic pain (PNP). While the benefit of low-concentration capsaicin remains controversial, the 8%-capsaicin patch (Qutenza®, 2010, Astellas, Netherlands) has shown its effectiveness. This patch is, however, costly and natural high-concentration capsaicinoid solutions may represent a cheaper alternative to pure capsaicin. Methods. In this retrospective study, 149 patients were screened, 132 were included with a diagnosis of neuropathic pain, and eighty-four were retained in the final analyses (median age: 57.5 years [IQR25–75: 44.7–67.1], male/female: 30/54) with PNP who were treated with topical applications of natural high-concentration capsaicinoid solutions (total number of applications: 137). Indications were postsurgical PNP (85.7%) and nonsurgical PNP (14.3%) (posttraumatic, HIV-related, postherpetic, and radicular PNP). Objectives. To assess the feasibility of topical applications of natural high-concentration capsaicinoid solutions for the treatment of PNP. Results. The median treated area was 250 cm² [IQR25–75: 144–531]. The median amount of capsaicinoids was 55.1 mg [IQR25–75: 28.7–76.5] per plaster and the median concentration was 172.3 μg/cm² [IQR25–75: 127.6–255.2]. Most patients had local adverse effects on the day of treatment, such as mild to moderate burning pain and erythema. 13.6–19.4% of the patients experienced severe pain or erythema. Following treatment, 62.5% of patients reported a lower pain intensity or a smaller pain surface, and 35% reported a sustained pain relief lasting for at least 4 weeks. Conclusion. Analgesic topical treatment with natural high-concentration capsaicinoid is feasible and may represent a low cost alternative to alleviate PNP in clinical practice.

Capsaicin 8 % Patch: A Review in Peripheral Neuropathic Pain

The capsaicin 8 % patch (QUTENZA®) is an adhesive patch containing a high concentration (8 % w/w) of synthetic capsaicin, a selective agonist of transient receptor potential vanilloid 1 channel. It is approved for treatment of peripheral neuropathic pain in adults either alone or in combination with other medicinal products for pain in the EU; it is only approved to treat postherpetic neuralgia (PHN) in the USA. In patients with painful diabetic peripheral neuropathy (PDPN), a single 30-min application of the capsaicin 8 % patch significantly improved pain relief and sleep quality compared with placebo in a 12-week double-blind trial. In a 52-week, randomized trial, up to seven consecutive 30-min treatments with the capsaicin 8 % patch (≤7 treatments each at least 8 weeks apart) plus standard of care therapy was associated with sustained pain relief and no negative neurological safety consequences compared with standard of care. In two randomized trials, a single 60-min application of the capsaicin 8 % patch reduced pain scores significantly more than a low-concentration (0.04 %) capsaicin control patch in patients with PHN. Capsaicin 8 % patch treatment was noninferior to pregabalin (optimized dosage) in a randomized trial in patients with nondiabetic peripheral neuropathic pain. Results in two trials in patients with HIV-AN were equivocal, with a significant improvement in pain intensity observed in one trial, but not in the other. The capsaicin 8 % patch was associated with expected, transient, capsaicin-related application-site adverse events such as erythema and pain.

Profile of the capsaicin 8% patch for the management of neuropathic pain associated with postherpetic neuralgia: safety, efficacy, and patient acceptability

Capsaicin is a naturally occurring irritant active ingredient found in hot peppers. It is a ligand for transient receptor potential channel vanilloid receptors, which are found in nociceptive nerve terminals in the skin. Initial exposure to topical capsaicin leads to excitation of these receptors, release of vasoactive mediators, erythema, intense burning, pain, and thereafter desensitization of sensory neurons resulting in inhibition of pain transmission. Capsaicin 8% has been licensed for the treatment of postherpetic neuralgia pain in recent years. A single application of high-concentration capsaicin for 60 minutes for postherpetic neuralgia has been robustly evaluated. Capsaicin 8% patches are applied to the most painful areas of healthy skin and allowed to remain for 60 minutes. Treatment can be repeated every 90 days if the pain persists or returns. The patches are usually applied in specialist pain clinics where patients can be pretreated and monitored. Health care staff need to take certain precautions before administering these patches to avoid unintentional contact. Common adverse effects of the capsaicin 8% patch are transient mild-to-moderate self-limiting application-site burning, pain, erythema, pruritus, papules, swelling, dryness, and hypertension. To manage local pain from capsaicin application, the skin is pretreated with a local anesthetic such as topical lidocaine or an oral analgesic such as oxycodone for up to 5 days. A transient increase in pain is usually seen within 48 hours of patch application before the pain-relieving effect starts. Systemic absorption is minimal and clinically insignificant. The nature of administration and relatively high cost of capsaicin patches can significantly limit their use to a small number of patients with severe refractory symptoms. This review highlights recent evidence related to the use and effectiveness of the 8% capsaicin patch for Postherpetic Neuralgia and discusses its safety and side-effect profiles.

Managing Neuropathic Pain

Neuropathic pain (NP) arises from injuries or diseases affecting the somatosensory component of the nervous system at any level of the peripheral or central nervous system. NP is diagnosed based on common neurologic signs and symptoms. NP is best treated with a combination of multiple therapeutic approaches, and treatments include conservative, complementary, medical, interventional, and surgical treatment modalities. Goals of treatment are the same as in pain management and include improvement in pain control and in coping skills as well as restoration of functional status. Most patients with NP benefit most from an individualized, multimodal approach that emphasizes both pain and function.

Recent Developments in Neuropathic Pain Mechanisms: Implications for Treatment

Neuropathic pain is defined as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system".Characteristic symptoms include an increased evoked pain response to noxious (hyperalgesia) and innocuous (allodynia) stimuli, spontaneous pain, shooting electric shock like pain. Sensory deficits can also exist.Available treatments are not adequate in many patients due to many factors including the complexity of the pain state, disease progression, intolerable side effects and low analgesic efficacy.A number of peripheral, spinal and supraspinal mechanisms of hyperexcitability underlie neuropathic pain, these include changes in the activity and expression of voltage gated sodium, calcium and potassium channels, as well as TRPV1 channels and alterations in the activity of neuroimmue pathways.NeP patients often experience depression, anxiety, sleep disturbances etc. alongside their pain. These co-morbidites significantly reduce quality of life and as such are key treatment considerations..Improved understanding of NeP mechanisms is encouraging targeting of treatment to the mechanisms that produce painful symptoms as opposed to the etiology of disease.

Treatment of painful diabetic peripheral neuropathy

BACKGROUND

Painful diabetic peripheral neuropathy impairs quality of life and can be difficult to treat.

OBJECTIVE

To discuss current treatment recommendations for painful diabetic peripheral neuropathy.

STUDY DESIGN

Literature review.

METHODS

Systematic review of the literature discussing treatment of painful diabetic peripheral neuropathy. Existing treatment guidelines were studied and compared.

RESULTS

Painful diabetic peripheral neuropathy occurs in about one in six people with diabetes. This condition impairs quality of life and increases healthcare costs. Treatment recommendations exist, but individual patient therapy can require a trial-and-error approach. Many treatment options have adjuvant benefits or side effects which should be considered prior to initiating therapy. Often, a combination of treatment modalities with various mechanisms of action is required for adequate pain control. Adequate medication titration and a reasonable trial period should be allowed.

CONCLUSION

The treatment of painful diabetic peripheral neuropathy can be challenging, but effective management can improve patient's quality of life.

CLINICAL RELEVANCE

Painful diabetic peripheral neuropathy impairs quality of life and can be difficult to treat. Many treatment options have adjuvant benefits or side effects which should be considered prior to initiating therapy. Often, a combination of treatment modalities with various mechanisms of action is required for adequate pain control.

Structural and functional assessment of skin nerve fibres in small-fibre pathology

Damage to nociceptor nerve fibres may give rise to peripheral neuropathies, some of which are pain free and some are painful. A hallmark of many peripheral neuropathies is the loss of small nerve fibres in the epidermis, a condition called small-fibre neuropathy (SFN) when it is predominantly the small nerve fibres that are damaged. Historically, SFN has been very difficult to diagnose as clinical examination and nerve conduction studies mainly detect large nerve fibres, and quantitative sensory testing is not sensitive enough to detect small changes in small nerve fibres. However, taking a 3-mm punch skin biopsy from the distal leg and quantification of the nerve fibre density has proven to be a useful method to diagnose SFN. However, the correlation between the nerve fibre loss and other test results varies greatly. Recent studies have shown that it is possible not only to extract information about the nerve fibre density from the biopsies but also to get an estimation of the nerve fibre length density using stereology, quantify sweat gland innervation and detect morphological changes such as axonal swelling, all of which may be additional parameters indicating diseased small fibres relating to symptoms reported by the patients. In this review, we focus on available tests to assess structure and function of the small nerve fibres, and summarize recent advances that have provided new possibilities to more specifically relate structural findings with symptoms and function in patients with SFN.

Cutaneous drug delivery of capsaicin after in vitro administration of the 8% capsaicin dermal patch system

OBJECTIVE

Epicutaneous application of capsaicin causes a long-lasting analgesic effect by binding to the membrane transient receptor potential vanilloid 1 (TRPV1) on mechanoheat-sensitive C and Aδ fibres, changing axonal integrity and inhibiting neurogenic inflammatory processes. To date, no information is available regarding the cutaneous drug delivery of capsaicin following patch application.

METHODS

Using a Franz diffusion cell, the cutaneous concentration-time profiles 30, 60 and 90 min after application of a patch containing 8% capsaicin (640 µg/cm(2)) on ex vivo thin (mamma) and thick (plantar) human skin were investigated at 32 °C, and additionally at 42 °C for thin skin and 10 °C for thick skin. An HPLC-MS method was used for the analytic detection of capsaicin.

RESULTS

The results show that already after a 30-min application of the 8% capsaicin patch, an equilibrium reservoir can be found in the stratum corneum in both thick and thin skin. Under physiological temperature conditions, a sufficient bioavailability of capsaicin in the cutaneous target compartments can be found. Raising the temperature to 42 °C has no relevant impact on the concentration-time profile, while reducing the temperature to 10°C leads to a significantly lower bioavailability.

CONCLUSION

After 30 min of application, a sufficient cutaneous bioavailability of capsaicin is reached in thick as well as thin skin. Whether shorter application times may suffice to achieve therapeutic effectiveness requires further investigation.

Application of the capsaicin 8% cutaneous patch in neuropathic pain of the head and face: A case series

INTRODUCTION

Treatment of neuropathic or neuralgic head and facial pain due to dental, traumatic or surgical nerve lesions or post-herpetic neuropathy is often challenging.

CASES

We are reporting on four patients with neuropathic pain syndromes successfully treated with a capsaicin 8% patch in the affected area of the head or face.

DISCUSSION

Treatment with the capsaicin 8% patch seems to be effective and safe for application to the facial and head region. The capsaicin 8% patch might be an additional treatment option if first-line treatment with anticonvulsants or antidepressants was ineffective or limited by side effects.

Capsaicin 8% patch for peripheral neuropathic pain: review of treatment best practice from 'real-world' clinical experience

SUMMARY The capsaicin 8% patch is licensed in Europe for the treatment of peripheral neuropathic pain in nondiabetic adults. In controlled trials it provided pain relief for up to 3 months with a single 30- or 60-min application. In this article, a group of pain specialists from Germany and the UK share their considerable experience of real-world use of the capsaicin 8% patch. This experience comes from treating >200 patients with a variety of neuropathic pain etiologies including postherpetic neuralgia, peripheral neuropathy and cancer-related neuropathy. These patients, a slight majority of whom were female, had experienced neuropathic pain for varied lengths of time (3 months to >15 years) and the majority were receiving concomitant medications for their pain at the time of capsaicin 8% patch treatment. Observations by the group suggest that patients with positive symptoms might respond best to therapy. To optimize response to treatment, the group reports that it is important to achieve good adhesion of the patch to the skin. The experience of the group is that the capsaicin 8% patch is a tolerable treatment and local anesthetic pretreatment may not always be required. Cooling measures used after treatments were found to be the most practical and beneficial means of relieving any treatment-related discomfort. The group observed that transient, clinically important increases in blood pressure owing to treatment-related discomfort are very rare and they have seen no correlation between treatment-related discomfort or erythema and response to treatment. In the real-life clinical setting, response to capsaicin 8% patch treatment may be higher than observed in the clinical trial program. Response to retreatment also appears to be equal to that of the first treatment, even in patients treated for the fifth time. It was also observed that patients receiving capsaicin 8% patch treatment are often able to reduce their intake of concomitant pain medications. Observations from real-life use of the capsaicin 8% patch will help to maximize its therapeutic potential.

Tolerability of the capsaicin 8% patch following pretreatment with lidocaine or tramadol in patients with peripheral neuropathic pain: a multicentre, randomized, assessor-blinded study

Background

Application of the capsaicin 8% patch is associated with treatment-related discomfort. Consequently, pretreatment for 60 min with anaesthetic cream is recommended; however, this may be uncomfortable and time consuming.

Methods

We conducted a multicentre, randomized (1:1), assessor-blinded study in patients with peripheral neuropathic pain to assess tolerability of the capsaicin patch following topical lidocaine (4%) or oral tramadol (50 mg) pretreatment. The primary endpoint was the proportion of patients tolerating capsaicin patch application (ability to receive ≥90% of a 60-min application). Numeric Pain Rating Scale (NPRS) scores were assessed before, during and after treatment.

Results

Overall, 122 patients were included (61 per arm). The capsaicin patch was tolerated by 121 patients. Tolerability of the capsaicin patch was similar following pretreatment with lidocaine and tramadol. Following patch application, pain levels increased up to 55 min (change from baseline of 1.3 for lidocaine and 1.4 for tramadol). After patch removal, tramadol-treated patients experienced greater pain relief up to the end of day 1; in the evening, mean changes in NPRS scores from baseline were 0 for lidocaine and −1 for tramadol. Proportions of patients reporting increases of ≥2 NPRS points or >33% from baseline at one or more time point(s) on the day of treatment were similar between arms. Adverse event incidence was comparable between arms.

Conclusions

Capsaicin 8% patch tolerability was similar in the two arms, with comparable results for most secondary endpoints. Tramadol given 30 min before patch application should be considered as an alternative pretreatment option in patients receiving capsaicin patch treatment.

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Capsaicinoids in the treatment of neuropathic pain: a review

The treatment of neuropathic pain is difficult. Oral pharmaceuticals have significant side effects, and treatment efficacy tends to be modest. The use of topical analgesics reduces the potential for systemic side effects and allows direct application of medications to the area of pain. The natural spicy substance, capsaicin, has historically been known for its topical use. Capsaicin, once applied to the skin, causes a brief initial sensitization followed by a prolonged desensitization of the local pain nerves. This occurs through stimulation of the transient receptor potential vanilloid-1 (TRPV1) expressing pain nerve fibers. While low-dose capsaicin has not resulted in good efficacy, the larger dose 8% topical capsaicin has had some of the best data currently available in the treatment of post-herpetic neuralgia (PHN) and other neuropathic conditions. This paper discusses the data currently existing for capsaicin 8% in the treatment of PHN. It further reviews data for the low-dose capsaicin products and the current status in the development of other capsaicinoids, e.g. resiniferotoxin, and high-concentration liquid capsaicin.

Topical capsaicin formulations in the management of neuropathic pain

This chapter reviews the scientific and clinical evidence supporting the use of topical formulations containing the pungent principle of chili peppers--capsaicin, for the treatment of peripheral neuropathic pain. Given the limitations of current oral and parenteral therapies for the management of pain arising from various forms of nerve injury, alternate therapeutic approaches that are not associated with systemic adverse events that limit quality of life, impair function, or threaten respiratory depression are critically needed. Moreover, neuropathic conditions can be complicated by progressive changes in the central and peripheral nervous system, leading to persistent reorganization of pain pathways and chronic neuropathic pain. Recent advances in the use of high-dose topical capsaicin preparations hold promise in managing a wide range of painful conditions associated with peripheral neuropathies and may in fact help reduce suffering by reversing progressive changes in the nervous system associated with chronic neuropathic pain conditions.

Thermo-sensitive TRP channels in peripheral nerve injury: a review of their role in cold intolerance

One of the sensory complications of traumatic peripheral nerve injury is thermal intolerance, which manifests in humans mainly as cold intolerance. It has a major effect on the quality of life, and adequate therapy is not yet available. In order to better understand the pathophysiological background of thermal intolerance, we focus first on the various transient receptor potential (TRP) channels that are involved in temperature sensation, including their presence in peripheral nerves and in keratinocytes. Second, the role of thermo-sensitive TRP channels in cold and heat intolerance is described showing three different mechanisms that contribute to thermal intolerance in the skin: (a) an increased expression of TRP channels on nerve fibres and on keratinocytes, (b) a lower activation threshold of TRP channels and (c) the sprouting of non-injured nerve fibres. Finally, the data that are available on the effects of TRP channel agonists and antagonists and their clinical use are discussed. In conclusion, TRP channels play a major role in temperature sensation and in cold and heat intolerance. Unfortunately, the available pharmaceutical agents that successfully target TRP channels and counteract thermal intolerance are still very limited. Yet, our focus should remain on TRP channels since it is difficult to imagine a reliable treatment for thermal intolerance that will not involve TRP channels.

A review of the high-concentration capsaicin patch and experience in its use in the management of neuropathic pain

In the European Union, the high-concentration capsaicin patch is licensed for the management of neuropathic pain conditions in nondiabetic patients, including postherpetic neuralgia (PHN) and HIV-associated distal sensory polyneuropathy (HIV-DSP). However, in the USA, the Food and Drug Administration approved its use only in PHN patients. Capsaicin is a transient receptor potential vanilloid-1 agonist, which increases the intracellular calcium ion concentration. This triggers calcium-dependent protease enzymes causing cytoskeletal breakdown and leads to the loss of cellular integrity and 'defunctionalization' of nociceptor fibres. Efficacy and therapeutic effect has been shown in several clinical studies of PHN and HIV-DSP. The high-concentration capsaicin patch and its practical application are different from low-concentration creams; one application can help for up to 3 months. The process of setting up of a service to use the capsaicin 8% patch is also discussed.

Options for treating postherpetic neuralgia in the medically complicated patient

Patients with postherpetic neuralgia (PHN) are often of advanced age or immunocompromised and likely to have ≥1 comorbid medical condition for which they receive ≥1 medication (polypharmacy). Comorbidities affecting renal or hepatic function can alter pharmacokinetics, thereby impacting the efficacy or tolerability of PHN analgesic therapies. Cardiovascular, cerebrovascular, or psychiatric comorbidities may increase patient vulnerability to potential adverse events associated with some PHN analgesic therapies. Because PHN is a localized condition, localized therapy with a topical analgesic (lidocaine patch 5% and capsaicin 8% patch or cream) may provide adequate efficacy while mitigating the risk of systemic adverse events compared with oral analgesics (eg, tricyclic antidepressants, anticonvulsants, opioids). However, combined therapy with a topical and an oral analgesic or with >1 oral analgesic may be needed for optimal pain management in some patients. This review summarizes how comorbidities and concomitant medications should be taken into account when selecting among available pharmacotherapies for PHN and provides recommendations for the selection of therapies that will provide analgesia while minimizing the risk of adverse events.

Prospective, non-interventional study on the tolerability and analgesic effectiveness over 12 weeks after a single application of capsaicin 8% cutaneous patch in 1044 patients with peripheral neuropathic pain: first results of the QUEPP study

BACKGROUND

Reversible defunctionalisation of nociceptors by the TRPV1 agonist capsaicin in high concentration is an emerging new concept for the treatment of peripheral neuropathic pain.

OBJECTIVES

The capsaicin 8% cutaneous patch with a long-lasting effect for up to 3 months after a single application is available in Germany by prescription since October 2010. The aim of this study was to monitor its usage and therapeutic performance in clinical practice.

METHODS

Patients had a single patch application with up to 4 patches and were followed up after 7-14 days, 4, 8, and 12 weeks. Average pain intensity (NPRS-11), pain attacks, neuropathy symptoms, sleep parameters, quality of life, working capacity and concomitant neuropathic pain medication were assessed during at least two visits.

RESULTS

A total of 509 females (48.8%; effectiveness population N = 1044) and 531 males (50.9%) were included; the mean age was 61.2 ± 14.4 (SD) years. Postherpetic neuralgia was the most frequent diagnosis (31.9%), followed by postsurgical neuralgia (22.8%), post-traumatic neuropathy (12.4%), polyneuropathy (14.3%), and mixed pain syndromes (16.6%). Thirty and 50% responder rates were 42.7% and 23.7%, respectively, with a mean relative reduction of pain intensity during weeks 1-12 of 24.7% (1.1 SEM) and significant improvements in pain attacks, sleep duration and sleep quality, while the consumption of opioids and antiepileptics decreased significantly. In 106 patients (10.0%; safety population n = 1063) 146 adverse drug reactions (ADRs) were reported, mainly application site reactions (erythema, pain). A total of 27 serious ADRs were documented in 17 patients (1.6%).

CONCLUSIONS

Analgesic treatment of peripheral neuropathic pain with the capsaicin 8% cutaneous patch is safe and effective.

LIMITATIONS

The study did not include a control group; therefore, a comparison of the results with that of therapeutic alternatives is not justified.

The capsaicin 8% patch for neuropathic pain in clinical practice: a retrospective analysis

Objective

To investigate the response of patients with peripheral neuropathic pain (PNP) to capsaicin 8% patch treatment in a clinical setting.

Design

Retrospective analysis.

Setting

The Clinic for Pain Therapy and Palliative Medicine at the Medical Centre for the region of Aachen, Germany.

Subjects

Patients diagnosed with PNP who attended the clinic for capsaicin 8% patch treatment between January 13, 2010 and February 7, 2011.

Outcome Measures

Pain intensity was assessed using the Numeric Pain Rating Scale (NPRS) at baseline and following each capsaicin 8% patch treatment. Changes in prescribed concomitant neuropathic pain (NP) medications and response duration were recorded.

Results

Overall, 68 patients with PNP conditions, including facial neuropathy (severe trigeminal neuralgia in V2), polyneuropathy, post-herpetic neuralgia, and mononeuropathies, received 96 treatments with the capsaicin 8% patch. The 53 patients with a follow-up of ≥8 weeks demonstrated a 48.4% mean reduction in NPRS score from baseline to Weeks 1–8. Among the 37 responders (those exhibiting ≥30% reduction in NPRS score from baseline to Weeks 1–8), the median time to re-treatment was 125 days. Following treatment, there was a significant (P < 0.001) 54% reduction in the mean number of prescribed concomitant NP medications taken by patients.

Conclusions

This analysis demonstrates that in clinical practice, the capsaicin 8% patch provides rapid and sustained pain reductions in patients with a variety of PNP conditions and a significant reduction in prescribed concomitant NP medications. The capsaicin 8% patch can be a valuable addition to the NP treatment armory for certain patients.

NGX-4010, a capsaicin 8% patch, for the treatment of painful HIV-associated distal sensory polyneuropathy: integrated analysis of two phase III, randomized, controlled trials

Background

HIV-associated distal sensory polyneuropathy (HIV-DSP) is the most frequently reported neurologic complication associated with HIV infection. NGX-4010 is a capsaicin 8% dermal patch with demonstrated efficacy in the treatment of HIV-DSP. Data from two phase III, double-blind studies were integrated to further analyze the efficacy and safety of NGX-4010 and explore the effect of demographic and baseline factors on NGX-4010 treatment in HIV-DSP.

Methods

Data from two similarly designed studies in which patients with HIV-DSP received NGX-4010 or a low-concentration control patch (capsaicin 0.04% w/w) for 30 or 60 minutes were integrated. Efficacy assessments included the mean percent change from baseline in Numeric Pain Rating Scale (NPRS) scores to Weeks 2–12. Safety and tolerability assessments included adverse events (AEs) and pain during and after treatment.

Results

Patients (n = 239) treated with NGX-4010 for 30 minutes demonstrated significantly (p = 0.0026) greater pain relief compared with controls (n = 100); the mean percent change in NPRS scores from baseline to Weeks 2–12 was −27.0% versus −15.7%, respectively. Patients who received a 60-minute application of NGX-4010 (n = 243) showed comparable pain reductions (−27.5%) to patients treated for 30 minutes, but this was not statistically superior to controls (n = 115). NGX-4010 was effective regardless of gender, baseline pain score, duration of HIV-DSP, or use of concomitant neuropathic pain medication, although NGX-4010 efficacy was greater in patients not receiving concomitant neuropathic pain medications. NGX-4010 was well tolerated; the most common AEs were application-site pain and erythema, and most AEs were mild to moderate. The transient increase in pain associated with NGX-4010 treatment decreased the day after treatment and returned to baseline by Day 2.

Conclusions

A single 30-minute application of NGX-4010 provides significant pain relief for at least 12 weeks in patients with HIV-DSP and is well tolerated.

Trial registration

C107 = NCT00064623; C119 = NCT00321672