FDA Approves Nonnarcotic Pain Patch for Postherpatic Neuralgia
By Yael Waknine
Medscape Medical News
November 18, 2009 — The US Food and Drug Administration (FDA) has approved an 8% capsaicin dermal patch (Qutenza, made by Lohmann Therapie-Systems AD, marketed by NeurogesX, Inc) for the management of pain associated with postherpatic neuralgia (PHN).
The nonnarcotic product is unlikely to cause drowsiness or drug interactions and provides up to 12 weeks of localized pain relief per application. Each 1-hour session may involve up to 4 patches, cut as needed to conform to the painful area.
"PHN can be an excruciatingly painful condition that can affect many aspects of a patient's quality of life. Despite a variety of medications for pain, undesirable side effects often limit their use and therefore, the treatment of PHN continues to represent a significant unmet need," said Lynn Webster, MD, medical director at Lifetree Clinical Research in Salt Lake City, Utah, in a company news release. "Qutenza may provide a unique treatment option that works at the site of the pain and may be useful as a treatment option in combination with existing therapies."
The drug's approval was based on data from two 12-week, phase 3 clinical trials (n = 818) in which patients with PHN received a single 1-hour application of the 0.8% (640 μg/cm2) capsaicin patch or a low-concentration (3.2 μg/cm2) version; all patches were applied over a maximal surface area of 1000 cm2.
Results from both studies showed that use of the high-concentration capsaicin patch yielded significantly greater reductions in pain intensity from baseline at 8 weeks, as assessed using an 11-point Numeric Pain Rating Scale (study 1, ?29% ± 2% vs ?18% ± 2%; study 2, ?33% ± 2% vs ?26% ± 2%).
Adverse events most commonly reported in both studies included erythema, pain, pruritis, and papules at the application site during and shortly after patch use. The FDA recommends use of a local topical anesthetic before treatment. Acute pain during and after the procedure should be addressed with local cooling and/or analgesics.
Approximately 1% of patients on the 8% capsaicin patch discontinued the study because of adverse events, including application-site pain and associated increases in blood pressure.
Blood pressure changes averaged less than 10 mm Hg, although some patients had greater increases that persisted for about 2 hours after patch removal. Blood pressure should be carefully monitored for 1 hour after each application, and caution is advised when treating patients with unstable or poorly controlled hypertension or a recent history of cardiovascular or cerebrovascular events.
To avoid the risk for exposure of the eyes or mucous membranes, the capsaicin 8% patch should not be applied to the face or scalp. Patches should be removed gently using a rolling motion to avoid capsaicin aerosolization.
Capsaicin 8% patch previously was granted orphan drug status by the FDA in the treatment of PHN. Other potential applications currently under investigation include HIV-distal sensory polyneuropathy and diabetic neuropathy.