Adhesive capsaicin 8% patch for improved control of pain caused by chemotherapy-induced peripheral neuropathy in patients with multiple myeloma: A single-centre, seven-case series.

Background: Capsaicin is a highly selective agonist of the transient receptor potential vanilloid 1. The adhesive capsaicin patch provides a high capsaicin concentration (8%) directly in the painful area - its efficacy in benign peripheral neuropathic pain (diabetic neuropathy or postherpetic neuralgia) has recently been described in the literature. However, there is scant evidence of its efficacy in chemotherapy-induced peripheral neuropathy (CIPN). This is a concern for patients with multiple myeloma, who suffer from peripheral neuropathic pain induced by first-line treatments (bortezomib or thalidomide).

Aim: To describe improved control of CIPN in patients with multiple myeloma using adhesive capsaicin 8% patch.

Methods: We opted for a retrospective observational case series. Between October 2017 and October 2020, we collected clinical data from adult multiple myeloma patients affected by CIPN who were administered the capsaicin 8% patch in our palliative care outpatient clinic. We compiled Numerical Pain Rating Scale (NPRS) scores, patients' medication needs and performance status before and after patch application.

Results: Two women and five men with an average age of 62.85 years received bortezomib. Two patients (28.57% of the sample) also received thalidomide. The average NPRS score before patch application was 6.42/10. Five of the seven patients (71.42%) received a mean daily oral morphine dose of 52.85 mg/day, five (71.42%) received gabapentinoids and one (14.28%) received antidepressants. The average NPRS score decreased to 4/10 seven days after patch application, while the mean daily oral morphine dose remained stable. Performance status improved slightly in two patients (28.57%) and remained stable in the rest. One patient (14.28%) required an extra analgesic dose during patch application.

Conclusions: Capsaicin 8% patch application appears to reduce pain intensity in patients with multiple myeloma suffering from CIPN.