0.075% Capsaicin cream and wind up in chronic lumbar radicular neuropathic pain - a phenotype-stratified, case series.

Authors: Emanuel Schembri, Ethel Carboni Jardim , Victoria Massalha, Carmel Abela

Corresponding: Emanuel Schembri (lelid26@gmail.com)

Keywords: Radiculopathy, Sciatica, Capsaicin, Phenotype, Precision Medicine, Low Back Pain, Case Reports

Doi: 10.7423/XJENZA.2024.2.06

Issue: Xjenza Online Vol. 12 Issue 1

Abstract:
Personalized treatment for low back pain disorders is a high research priority and stratified medicine using sensory profiling can potentially improve the outcomes. Wind up, or temporal summation is the progressive increase in action potential firing rate of spinal cord neurons to repetitive stimulation of C-fibre afferents at a constant intensity. Wind up can occur in neuropathic pain, and it is augmented by the presence of central sensitization, which can lead to Aδ-fiber induced wind up rather than solely being activated by C-fibre stimuli. Topical capsaicin activates the transient receptor vanilloid-1, which is expressed in C-fibres and some Aδ-fibers of the peripheral nervous system, leading to a reduction in skin evoked pain. Despite the supporting evidence for the 8% capsaicin patch, there is evidence that specific patient subgroups treated with 0.04% capsaicin formulation obtained better analgesia compared to the higher dose. However, that research did not evaluate sensory profiles nor predictive biomarkers.
Due to the shared neurophysiological mechanisms underlying wind up and capsaicin, we hypothesized that the application of a low dose capsaicin cream (0.075%), in conjunction with physiotherapy, could provide analgesia in a phenotype-stratified case series (n=9) diagnosed with chronic lumbar radicular neuropathic pain (median 5 years), and exhibiting wind up. The combination of physiotherapy and topical capsaicin cream yielded clinically significant analgesia (Hedges’ g = 2.96). Hence the hypothesis of using a simple bedside test for wind up as a prognostic biomarker for positive outcomes from capsaicin cream in patients with chronic lumbar radiculopathies, should be investigated in a randomized controlled trial.

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