Long-term Treatment with Capsaicin 8%: A Subgroup Analysis in Patients with PHN

AIM OF INVESTIGATION: The high concentration capsaicin 8% topical system (HCCTS) is commonly recommended as a second line therapy for PHN. HCCTS delivers the drug effectively and directly to the skin while limiting the risk of systemic effects and drug interactions. The STRIDE study was designed to investigate the long-term safety of repeated HCCTS administration in patients with non-diabetic neuropathic pain (Gálvez et al., 2017). The present analysis measures patient outcomes among a subgroup of patients with PHN included in the STRIDE study. Methods STRIDE was an open-label, multicenter, 52-week observational trial conducted in Europe. Prior treatment with HCCTS and a history of diabetes were among the exclusion criteria. Patients received up to 6 HCCTS treatments at 9- to 12-week intervals. At each application visit, a maximum of 4 HCCTSs equivalent to an area of up to 1120 cm2 were applied for 60 minutes. HCCTS retreatment was at the investigator's discretion and according to patient feedback. Long-term tolerability and safety were the primary objectives of the study. Areas of spontaneous pain and allodynia were monitored, and scales were used to assess pain, quality of life and treatment outcome at each retreatment. Results Average daily pain as rated on the numeric pain rating scale decreased from 6.6 (SD, 1.46) at baseline to 5.0 (SD, 1.99) after 6 months and 4.6 (2.18) after 12 months. Over 50% of patients showed at least minimal improvement on the Patient Global Impression of Change. The area of allodynia/hyperplasia decreased during the study by just over 20%. Overall, repeated HCCTS application was well-tolerated in patients with PHN. Conclusions HCCTS repeat application over 12 months in patients with PHN was well tolerated. Moreover, progressive and sustained reduction in pain intensity was achieved, as well as reductions in the area of allodynia and spontaneous pain.