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| |  High-Concentration Capsaicin Patch Provides Pain Relief in Diabetic Neuropathy, HIV Polyneuropathy, and Postherpetic Neuralgia: Presented at AAPM By Emma Hitt, PhD HONOLULU -- January 30, 2009 -- A high-concentration capsaicin patch, NGX-4010, is effective in treating painful diabetic neuropathy (PDN), painful HIV-distal sensory polyneuropathy (HIV-DSP), and postherpetic neuralgia (PHN), according to results from 2 open-label, multicentre studies. The studies were presented here on January 29 at the American Academy of Pain Medicine (AAPM) 25th Annual Meeting. In the first study, Lynn Webster, MD, Lifetree Clinical Research & Pain Clinic, Salt Lake City, Utah, and colleagues enrolled 91 patients with PDN with moderate to severe pain in both feet. Patients received pretreatment with a topical anaesthetic followed by a single NGX-4010 treatment applied for 60 or 90 minutes. Outcomes were compared with baseline measures. Overall, patients achieved a mean decrease of 32% in pain scores from baseline during weeks 2 to 12, while 48% of patients demonstrated a response, as indicated by at least a 30% decline in pain scores from baseline. The most common adverse event was local application-site reaction. The second study involved a safety analysis of repeated applications of NGX-4010 over 1 year in 106 patients with HIV-DSP or PHN. Topical administration of 4% lidocaine was followed by a single 60-minute (PHN and HIV-DSP) or 90-minute (HIV-DSP) treatment with NGX-4010. Patients were allowed to receive up to 3 additional applications spaced at least 3 months apart. A total of 293 NGX-4010 treatments were administered. Adverse events were generally transient and included redness at the application site in up to 96% of applications, pain in up to 73% of applications, and oedema in up to 11% of applications. The incidence of adverse events did not appear to be associated with the number of applications or improvement in pain outcomes. Transient changes in blood pressure were noted. "Adverse events were as [had been] expected, and we were encouraged that we did not see any sensory function changes or systemic adverse events with our treatment over 48 weeks, even with repeated applications," said the study's lead author, David M. Simpson, MD, Mount Sinai School of Medicine, New York, New York. The transient receptor potential vanilloid receptor (TRPV1) is expressed in nociceptive fibres that perceive pain, Dr. Simpson said in an interview. Capsaicin is a TRPV1 agonist that causes desensitisation of TRPV1 channels with an analgesic effect. NGX-4010 contains a form of synthetic capsaicin, known as trans-capsaicin, at an 8% concentration that is delivered directly to the pain site. According to the manufacturers, findings from clinical trials suggest that a single topical application of NGX-4010 may provide 3 months of pain relief with minimal potential for adverse effects or drug-drug interactions. The new drug application for NGX-4010 was accepted by the US Food and Drug Administration in December 2008, and approval for marketing is expected in late 2009, according to the drug's manufacturer, NeurogesX Inc., which provided funding for these studies.
[Presentation titles: NGX-4010, a High-Concentration Capsaicin Patch, in Painful Diabetic Neuropathy (PDN). Abstract 224. Long-Term Safety of NGX-4010, a High-Concentration Capsaicin Patch, for the Treatment of Neuropathic Pain in Patients With Painful HIV-Distal Sensory Polyneuropathy (HIV-DSP) or Postherpetic Neuralgia (PHN). Abstract 225]
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