Progressive Response to Repeat Application of Capsaicin 179 mg (8% w/w) Cutaneous Patch in Peripheral Neuropathic Pain: Comprehensive New Analysis and Clinical Implications

Objective. To investigate the efficacy of repeated application of capsaicin 179 mg cutaneous patch in nonresponders to the first application. Design. Post hoc, as-treated analysis of two prospective trials (STRIDE and PACE) with 52-week follow-up. Blinding. Open-label. Setting. Multicenter clinical trial. Subjects. STRIDE: nondiabetic neuropathic pain; PACE: painful diabetic peripheral neuropathy. Methods. Patients were divided according to number of applications needed before attainment of a >= 30% reduction in average pain intensity (question 5 of the Brief Pain Inventory [BPI-Q5]). We assessed the change from baseline in average pain intensity (BPI-Q5), mean "interference with sleep" score, Patient Global Impression of Change, quality of life (QOL) via the EuroQol 5-dimension, and Self-Assessment of Treatment. Results. In STRIDE and PACE, respectively, n = 306 and n = 313 received the capsaicin patch; n = 60 and n = 96 had a response after the first application, n = 33 and n = 68 after the second, and n = 11 and n = 43 after the third. Among patients without a >= 30% reduction in pain intensity at 3 months, in STRIDE and PACE, respectively, 23.3% and 28.1% achieved a >= 30% reduction at 6 months, increasing to 33.9% and 45.7% at 12 months. Similar results were obtained when a decrease of >= 50% was used as the responder definition. Progressive improvements in pain intensity in slower responders reached levels similar to those in early responders at month 12 and were accompanied by improvements in sleep, QOL, and patient satisfaction. Conclusions. Although some patients with peripheral neuropathic pain experience rapid improvements with a single treatment of capsaicin 179 mg patch, some may require two or three treatments before an initial response is observed. Similar benefits for pain, sleep, and QOL can be achieved in early and late responders.