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      Tolerability of NGX-4010, a capsaicin 8% patch, in conjunction with three topical anesthetic formulations for the treatment of neuropathic pain

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          Abstract

          Background

          The objective of this study was to assess the safety, tolerability, and preliminary efficacy of NGX-4010, a capsaicin 8% patch, following pretreatment with three different topical anesthetics in patients with peripheral neuropathic pain.

          Methods

          This open-label, multicenter study enrolled 117 patients with post-herpetic neuralgia, HIV-associated distal sensory polyneuropathy, or painful diabetic neuropathy. Patients received pretreatment with one of three lidocaine 4%-based topical anesthetics (L.M.X.4 ® [Ferndale Laboratories Inc, Ferndale, MI], Topicaine ® Gel [Estela Basso, Jupiter, FL], or Betacaine Enhanced Gel 4 [Tiberius Inc, Tampa, FL]) for 60 minutes followed by a single 60- or 90-minute NGX-4010 application, and were followed for 12 weeks. Tolerability and safety measures included “pain now” Numeric Pain Rating Scale (NPRS) scores, dermal assessments, medication use for treatment-related pain, adverse events (AEs), clinical laboratory parameters, physical examinations, and vital signs. The primary efficacy variable was the percentage change in mean NPRS scores for “average pain for the past 24 hours” from baseline to weeks 2 through 12.

          Results

          Treatment with NGX-4010 following pretreatment with any of the three topical anesthetics was generally safe and well tolerated. Nearly all patients completed ≥90% of the planned NGX-4010 application duration. The most common treatment-related AEs, application-site burning and application-site pain, were transient, mostly mild or moderate, and could be adequately managed by local cooling or short-acting oral opioid analgesics. Although slightly more patients used medication for treatment-related discomfort following pretreatment with Topicaine compared with L.M.X.4 or Betacaine, there were no statistical differences between the topical anesthetics. Neuropathic pain reduction from baseline to weeks 2 through 12 was approximately 30% and was similar among the topical anesthetics; the proportion of responders ranged from 45% to 50%.

          Conclusion

          Treatment with NGX-4010 following pretreatment with any of the three topical anesthetics was generally safe and well tolerated; no significant differences in the parameters measured were noted between the pretreatment groups.

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          Most cited references 22

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          Vanilloid (Capsaicin) receptors and mechanisms.

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            Controlled trial of high-concentration capsaicin patch for treatment of painful HIV neuropathy.

            HIV-associated distal sensory polyneuropathy (HIV-DSP) is a painful condition with limited effective treatment. Capsaicin desensitizes cutaneous nociceptors resulting in reduced pain. We report a placebo-controlled study of a high-concentration capsaicin dermal patch (NGX-4010) for the treatment of painful HIV-DSP. This double-blind multicenter study randomized 307 patients with painful HIV-DSP to receive NGX-4010 or control, a low-concentration capsaicin patch. After application of a topical anesthetic, NGX-4010 or control was applied once for 30, 60, or 90 minutes to painful areas on the feet. The primary efficacy endpoint was percent change in Numeric Pain Rating Scale (NPRS) from baseline in mean "average pain for past 24 hours" scores from weeks 2 to 12. A single NGX-4010 application resulted in a mean pain reduction of 22.8% during weeks 2 to 12 as compared to a 10.7% reduction for controls (p = 0.0026). Following a transient treatment-related pain increase, pain was reduced; significant improvement was apparent by week 2 and continued throughout the controlled 12-week observation period. Mean pain reductions in the NGX-4010 30-, 60- and 90-minute groups were 27.7%, 15.9%, and 24.7% (p = 0.0007, 0.287, and 0.0046 vs control). One third of NGX-4010-treated patients reported >or=30% pain decrease from baseline as compared to 18% of controls (p = 0.0092). Self-limited, mild-to-moderate local skin reactions were commonly observed. A single NGX-4010 application was safe and provided at least 12 weeks of pain reduction in patients with HIV-associated distal sensory polyneuropathy. These results suggest that NGX-4010 could provide a promising new treatment for painful HIV neuropathy.
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              A randomized, controlled, open-label study of the long-term effects of NGX-4010, a high-concentration capsaicin patch, on epidermal nerve fiber density and sensory function in healthy volunteers.

              Desensitization of nociceptive sensory nerve endings is the basis for the therapeutic use of capsaicin in neuropathic pain syndromes. This study evaluated the pharmacodynamic effects of a single 60-minute application of NGX-4010, a high-concentration (8% w/w) capsaicin patch, on both thighs of healthy volunteers. Epidermal nerve fiber (ENF) density and quantitative sensory testing (QST) using thermal, tactile, and sharp mechanical-pain (pinprick) stimuli were evaluated 1, 12 and 24 weeks after capsaicin exposure. After 1 week, there was about an 80% reduction of ENF density compared to unexposed sites. In addition, there was about an 8% increase in tactile thresholds compared to baseline and the proportion of stimuli reported as sharp mechanical pain decreased by about 15 percentage points. Twelve weeks after exposure to capsaicin, ENF regeneration was evident, but not complete, and sharp mechanical-pain sensation and tactile thresholds did not differ from unexposed sites. Nearly full (93%) ENF recovery was observed at 24 weeks. No statistically significant changes in heat- or cold-detection thresholds were observed at any time point. NGX-4010 was generally well tolerated. Transient, mild warming or burning sensations at the site of application were common adverse effects. This article evaluates the effect of a single 60-minute NGX-4010 application on ENF density and QST in healthy volunteers followed for 24 weeks. The results help predict the long-term safety of NGX-4010 applications in patients. Copyright (c) 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                J Pain Res
                J Pain Res
                Journal of Pain Research
                Dove Medical Press
                1178-7090
                2012
                20 January 2012
                : 5
                : 7-13
                Affiliations
                [1 ]Lifetree Clinical Research and Pain Clinic, Lifetree Medical Inc, Salt Lake City, UT, USA
                [2 ]Clinical Research Division, The Pain Treatment Center of the Bluegrass, Lexington, KY, USA
                [3 ]Altoona Center for Clinical Research, Duncansville, PA, USA
                [4 ]University of Pennsylvania, School of Medicine, Philadelphia, PA, USA
                [5 ]NeurogesX Inc, San Mateo, CA, USA
                Author notes
                Correspondence: Lynn R Webster, Lifetree Clinical Research, 3838 South 700 East, Suite 202, Salt Lake City, UT 84106, USA, Tel +1 801 269 8200, Fax +1 801 261 3341, Email LRWebsterMD@ 123456gmail.com
                Article
                jpr-5-007
                10.2147/JPR.S25272
                3273402
                22328830
                © 2012 Webster et al, publisher and licensee Dove Medical Press Ltd.

                This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.

                Categories
                Original Research

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