Treatment of neuropathic pain with the capsaicin 8% patch: is pretreatment with lidocaine necessary?

Abstract

The capsaicin 8% patch can effectively treat neuropathic pain, but application can cause discomfort or a burning sensation. Until March 2013, it was recommended that patients be pretreated with a topical anesthetic, for example lidocaine, before capsaicin patch application. However, speculation existed over the need for pretreatment and its effectiveness in alleviating treatment-associated discomfort. This article compares tolerability to and efficacy of the capsaicin patch in pretreated and non-pretreated patients. All patients received a single capsaicin patch application. Pretreated patients received a lidocaine plaster before and intravenous lidocaine and metamizole infusions during capsaicin patch application. Pain levels, assessed using a Numeric Rating Scale (NRS), were used to determine tolerability and efficacy. All patients (pretreated n = 32; non-pretreated n = 26) completed 100% of the intended capsaicin patch application duration. At the time of capsaicin patch removal, 69% of pretreated and 88% of non-pretreated patients reported an NRS score increase, which returned to baseline by 6 hours post-treatment. There was no significant difference in mean NRS score between patient groups at any time during or after capsaicin patch treatment. Response was similar between patient groups; capsaicin patch treatment provided rapid and significant pain reductions that were sustained over 12 weeks. The same proportion of pretreated and non-pretreated patients reported willingness to receive retreatment with the capsaicin patch. This analysis shows that the capsaicin 8% patch is generally tolerable, and the small discomfort associated with patch application is short-lived. Lidocaine pretreatment does not have a significant effect on tolerability, efficacy, or patient willingness to receive retreatment.

Keywords: capsaicin; lidocaine pretreatment; nerve pain; neuralgia; nociceptors; peripheral nervous system; tolerability; topical.

Figure 1

Change in pain score from baseline at removal of capsaicin 8% patch. Data for individual patients receiving lidocaine pretreatment (n = 32) and receiving no pretreatment (n = 26) are shown, ordered by size of change in Numeric Rating Scale (NRS) score from baseline.

Figure 2

Mean pain scores (±SD) for pretreated and non-pretreated patients during the first 24 hours after capsaicin 8% patch treatment. P values for pretreated (n = 32) vs. non-pretreated (n = 26) patients were calculated using a t-test for equality of means, not assuming equal variance, and using the Mann–Whitney U-test that compares ranks and is therefore not affected by the distribution of the dependent variable. P values from the Mann–Whitney U-test are presented in brackets.

Figure 3

Change in pain score from baseline in pretreated and non-pretreated patients. (A) Change in absolute Numeric Rating Scale (NRS) score and (B) percentage change in NRS score from baseline (mean pain score during the week before treatment) is shown. P values for pretreated (n = 32) vs. non-pretreated (n = 24) patients were calculated using a t-test for equality of means, not assuming equal variance, and using the Mann–Whitney U-test that compares ranks and is therefore not affected by the distribution of the dependent variable. P values from the Mann–Whitney U-test are presented in brackets.

Figure 4

Proportion of patients stating that they would be happy to receive capsaicin 8% patch retreatment when necessary. Patients were asked to record if they would be willing to receive capsaicin 8% patch retreatment 90 days after initial treatment. The proportion of pretreated and non-pretreated patients and the proportion of responders, classified as those patients with ≥ 30% decrease in NRS from baseline, and nonresponders willing to receive retreatment are shown.