The Effect of Topical Capsaicin 8% on Pain in Chemotherapy-induced Peripheral Neuropathy.

Abstract

Background: Chemotherapy-induced peripheral neuropathy (CIPN) can cause chemotherapy dose reductions and impact patients' quality of life. Few proven treatments exist, with generally modest analgesic effects and possible side effects. Small studies show the beneficial effects of topical capsaicin 8% on pain.

Aim: To investigate capsaicin's effects on pain, neurotoxicity, and mood in patients with CIPN.

Design: Prospective data collection in patients treated with capsaicin 8% for painful CIPN.

Methods: In 17 patients, data was collected before (t0) and directly (t1), 2 weeks (t2), and 8 weeks (t3) after capsaicin 8% treatment. Differences between t0-t2 and t0-3 were assessed for pain (Numeric Rating Scale [NRS]; acceptability), neurotoxicity symptoms (20-item questionnaire [CIPN20]; mechanical detection [MDT] and pain [MPT] thresholds), and mood (Hospital Anxiety and Depression Score [HADS]).

Results: For 9 patients (53%), pain became "acceptable" at t2 and t3, with a significant reduction (pain intensity difference [PID]_t0-2: -1.72, PID_t0-3: -2.47, both p < .001), whereas average NRS did not change significantly for patients scoring "unacceptable." HADS anxiety scores remained unchanged, whereas depression scores decreased from baseline (t_0-2: -1.47, p = .014; t_0-3: -1.36, p = .021). CIPN20 decreased from baseline (t_0-2: -1.87, p = .004; t_0-3: -3.32 p = .002). MPT was significantly lower post-treatment and MDT did not change.

Conclusions: Capsaicin 8% can have a beneficial analgesic effect in patients with CIPN-related pain but with a marked "on-off" effect. Mood changes were marginal. Quantitative sensory testing findings do not support earlier findings on nerve degeneration after capsaicin treatment, although the study size was small for definitive conclusions.