For patients with peripheral neuropathic pain, treatment with capsaicin patch led to improvements in pain intensity, quality of life, sleep, and patient satisfaction. However, some achieved results immediately while others required multiple treatments to reach similar levels of improvement. These findings were published in Pain Medicine.
Researchers analyzed data from two prospective trials of repeat treatment with the capsaicin 179-mg cutaneous patch over 52 weeks. STRIDE (ClinicalTrials.gov identifier NCT01252160) included patients with nondiabetic neuropathic pain and PACE (ClinicalTrials.gov identifier NCT01478607) patients with painful diabetic peripheral neuropathy. Patients were divided based on the number of applications needed before a 30% or greater response on average pain intensity.
In STRIDE and PACE, 306 and 313 patients, respectively, each received a capsaicin patch. A response after the first application was achieved in 60 STRIDE and 96 PACE participants, in 33 and 68 participants after a second application, and 11 and 43 after a third, respectively.
The percentage of patients who did not have a 30% reduction in pain from baseline at 3 months but responded by 6 months was 23.3% in STRIDE and 28.1% for PACE. By 12 months, this was 33.9% and 45.7% for STRIDE and PACE participants.
For both trials, patients who responded only after the second treatment had slower declines in pain intensity but eventually achieved results similar to those of the early responders.
The responses to other efficacy endpoints such as sleep interference showed similar patterns. Patients with a pain response after a single treatment also had rapid reductions in sleep interference. For those achieving a pain response after the second treatment, declines in sleep interference were slower but again were ultimately like those of the early responders. Improvements in quality of life and patient satisfaction were also similar in all participants by month 12 of the trials.
Discontinuation rates in both trials were low and resulted from lack of efficacy or withdrawal of consent. Concomitant pain medications were a potential confounder, and in both trials, pregabalin or gabapentin were discontinued rather than initiated more often whereas opioids were initiated in a slightly higher proportion in patients who responded after the first and second treatments.
These results require prospective assessments to confirm, said researchers. Adding that missing data from withdrawn patients and a lack of comparative data to determine which improvements were due to therapy were further limitations.
The researchers concluded that “some patients experience rapid and long-lasting improvements in pain following a single local treatment” but “…others may follow a more progressive or incremental course of benefit in terms of pain, sleep, [quality of life] and patient satisfaction.” The mechanisms behind the progressive responses are not fully understood and further studies are warranted.
Disclosures: Some study authors declared affiliations with the biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Freynhagen R, Argoff C, Eerdekens M, Engelen S, Perrot S. Progressive response to repeat application of capsaicin 179 mg (8% w/w) cutaneous patch in peripheral neuropathic pain: comprehensive new analysis and clinical implications. Pain Med. Published online April 19, 2021. doi:10.1093/pm/pnab113