Pharmacology Update

Capsaicin Patch 8% (Qutenza™)

By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD. Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; and Assistant Professor of Medicine, University of California, San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Elliott and Chan report no financial relationship to this field of study.

The FDA has approved capsaicin in a high-concentration, matrix-formulated dermal patch. It is designed to deliver a therapeutic dose into the skin during a 60-minute application. Capsaicin patch is marketed by NeurogesX, Inc., as Qutenza™.

Indications

Capsaicin patch is indicated for the management of neuropathic pain associated with post-herpetic neuralgia.1

Dosage

Capsaicin patch is applied by a physician or health care provider to the most painful skin area for 60 minutes.1 Up to 4 patches may be used. Application may be repeated every 3 months or as needed if pain returns, but no more frequently than every 3 months. A topical anesthetic should be applied before capsaicin application. Blood pressure should be monitored during and after application.

Each patch contains 8% capsaicin (640 mg/cm2, 179 mg total).

Potential Advantages

Capsaicin patch has a low risk for systemic adverse events compared to oral medications (e.g., antidepressants, anticonvulsants). One application may provide analgesia for up to 12 weeks.

Potential Disadvantages

Transient changes in blood pressure have been observed on the day of administration. Changes were usually < 10 mm Hg and lasted for about 2 hours after patch removal.1,2 About 40% of patients experience pain at the application site and about 60% experience erythema.1 Local measures (e.g., ice pack) or analgesics may be needed to alleviate acute pain. The patch must be applied by a health care provider.

Comments

Transient receptor potential vanilloid 1 receptors (TRPV1) are upregulated during inflammatory conditions and, in animal models of diabetic neuropathy, new TRPV1 is present in neurons that do not normally express TRPV1.3 Capsaicin is a selective agonist for TRPV1. Activation of the TRPV1-expressing nociceptors produces burning, pain sensation, and erythema, which subsequently results in desensitization and inhibition of initiation of pain transmission.3,4 Capsaicin is poorly absorbed topically; therefore, a high concentration is required to provide desensitization.

The efficacy of a high-concentration patch was shown in two 12-week, double-blind, randomized, trials.1,2 Study subjects had post-herpetic neuralgia for at least 6 weeks following healing of herpes zoster rash and had a mean baseline score of 6 (range, 3-9) on an 11-point scale. Subjects were randomized to capsaicin patch (8%) or control (0.04%). Approximately 40% of subjects were on pain-controlling medication. Those on a stable dose were required to keep their doses stable during the study. Rescue medications were permitted up to 5 days after application. Pain scores were recorded in a diary. The primary endpoint was pain reduction at week 8. The percent changes were -29% vs -18% for study 1 and -33% and -26% for study 2 for capsaicin and control, respectively. Roughly 40% of subjects randomized to capsaicin 8% had a 3 30% improvement compared to about 30% for the control. Some subjects experienced pain relief at week 1.1 However, the magnitude of pain reduction appears to be similar to that reported for pregabalin.5

The benefit of capsaicin does not appear to be affected by concomitant use of neuropathic pain medication.2 The patch has been reported to provide pain relief in patients with painful HIV neuropathy.6 Capsaicin patch does not appear to affect warm, sharp, or vibratory sensation, or deep tendon reflexes.6 Most common adverse events were related to the pharmacodynamics of capsaicin and transient increase in blood pressure.

A 52-week open-label study presented in abstract form suggested that the drug is safe with repeated application.7

Clinical Implications

Capsaicin patch provides a nonsystemic alternative to antidepressants, anticonvulsants, and analgesics for the management of post-herpetic neuralgia. There are currently no published comparative trials with other neuropathic medication.

References

1. Qutenza Prescribing Information. San Mateo, CA: NeurogesX, Inc.; November 2009.

2. Backonja M, et al. NGX-4010, a high-concentration capsaicin patch, for the treatment of postherpetic neuralgia: A randomised, double-blind study. Lancet Neurol 2008;7:1106-1112.

3. Cortright DN, Szallasi A. Biochemical pharmacology of the vanilloid receptor TRPV1. An update. Eur J Biochem 2004;271:1814-1819.

4. Knotkova H, et al. Capsaicin (TRPV1 agonist) therapy for pain relief: Farewell or revival? Clin J Pain 2008; 24:142-154.

5. Lyrica Prescribing Information. New York, NY: Pfizer Pharmaceuticals; April 2009.

6. Simpson DM, et al; NGX-4010 C107 Study Group. Controlled trial of high-concentration capsaicin patch for treatment of painful HIV neuropathy. Neurology 2008;70:2305-2313.

7. Simpson D, et al. Boston, MA: American Academy of Neurology Annual Meeting; April 27-May 5, 2007: Abstract 2712.