AAN 2011: Qutenza Patch Reduces Postherpetic Neuralgia Pain in Multiple Subgroups of Patients

The capsaicin patch NGX-4010 (Qutenza) reduces pain from postherpetic neuralgia (PHN) regardless of age, duration of PHN, or multiple other criteria, according to a study presented at the 63rd Annual Meeting of the American Academy of Neurology.

NGX-4010 was approved in 2009 for treatment of PHN based on positive results from 4 Phase III trials enrolling more than 1100 patients of both sexes, with a wide range of PHN duration, baseline pain scores, and use of concomitant pain medications. The goal of the new study was to see if the benefit of treatment was limited to particular subgroups or clinical conditions.

Patients in the pivotal trials received a single 60-minute treatment with a patch containing 8% capsaicin, or a single treatment with a low-dose patch (0.04% capsaicin) for 30, 60, or 90 minutes (the control group). The primary endpoint was the mean percentage change in “average pain for the past 24 hours,” as recorded on the Numeric Pain Rating Scale (NPRS), rated from 0 (no pain) to 10 (worst possible pain). Comparison was made between the baseline score and the scores at weeks 2 to 8.

Capsaicin is an agonist of the transient receptor potential vanilloid 1 receptor, explained lead study author Miroslav Backonja, MD, Medical Director of Lifetree Center for Neuroscience Research in Salt Lake City, UT, which was involved in conducting the trial. The vanilloid 1 receptor is a key receptor involved in pain sensation, through two mechanisms. It reversibly reduces epidermal nerve fiber density, and reduces function of nociceptors, leading to reduced pain transmission.

Backonja pooled data from the 4 trials and then separated subgroups based on sex, age (below the median vs. equal to or above), use of concomitant pain medication (yes vs. no), and baseline NPRS score (below the median vs. equal to or above).

The mean reduction in NPRS score from baseline to weeks 2 to 8 was 31% for NGX-4010 versus 22% for control. Males and females benefited equally, Backonja's analysis showed. On average, women had greater baseline pain than men, but received equivalent percent reduction in pain from treatment.

Patients younger than the mean age of 73 years had more pain than older patients, but again achieved significant reduction from active treatment regardless of age. Duration of PHN did not affect baseline pain scores, or benefit from treatment. Patients taking concomitant pain medications had lower baseline pain scores than those not on pain medications. Both groups experienced significant pain reduction from treatment, with a slightly larger decrease in those not taking other medications.

The results, Backonja said, indicate that a single 1-hour treatment with NGX-4010 “can provide three months of pain relief associated with PHN, regardless of gender, age, PHN duration, baseline pain score, or use of systemic concomitant neuropathic pain medications.”

The study was sponsored by NeurogesX.