Capsaicin Patch Decreases Focal Neuropathic Pain, Improves Mobility

An 8% capsaicin patch for the treatment of focal neuropathic pain was found to improve pain, mobility, and quality of life among patients with spinal cord injury, according to the results of a study published in Pain Medicine.

Individuals (N=11) experiencing neuropathic pain more than 1 year after sustaining a spinal cord injury were recruited for this study at the University of Texas Health Science Center in 2016. The participants were randomly assigned to undergo treatment with the 8% capsaicin patch or control (low-dose [0.025%] capsaicin patch) on the first day of a 12-week block, and the treatment assignment was crossed over in a second 12-week block. The primary outcomes were change in pain on the visual analog scale (VAS) and Multidimensional Pain Inventory for SCI (MPI-SCI), change in ability to perform activities of daily living using the Spinal Cord Independence Measure (SCIM), and change in personal perception of quality of life using the World Health Organization Quality of Life (WHOQOL-BREF) questionnaire.

To apply the treatments, patients outlined the painful area using a sterile pen, applied a liberal amount of 2.5% lidocaine/2.5% prilocaine cream, and covered the area with transparent tape for 60 minutes. The tape was removed, and the skin was cleaned with isopropyl alcohol. The control or intervention patch was then applied to the area and secured with transparent tape for 60 minutes, following which the patch was removed and the area cleansed.

Mean age of the study population was 49.7±12.5 years. The average duration since spinal cord injury was 9.5±12.5 years previously, and 8 had a spinal cord injury graded as motor complete, 2 as motor incomplete, and 1 with completeness unknown.

Compared with the control patch, the 8% capsaicin patch was associated with a significant effect on VAS score overall (F_[1,95.9], 11.82; P =.00087) and on VAS scores at week 2 (mean difference [MD], -1.91 points; P =.029) and 4 (MD, -1.64; P =.049).

Treatment was associated with a significant main effect on MPI-SCI (F_[1,48.5], 4.46; P =.04); however, there was no significant change in MPI-SCI pain severity subscore at weeks 4, 8, or 12.

The investigators observed a significant change in the SCIM mobility subscore (F_[1,47.2], 5.55; P =.023) and a trend toward mobility improvement at week 6 (P =.12).

The investigators also observed a significant main effect of the 8% capsaicin patch on WHOQOL-BREF (F_[1,47.3], 7.90; P =.0072) and a 12.5-point (P =.01) improvement in the physical health score at week 12.

Major limitations of this study include its small sample size and short study duration.

This study found evidence that an 8% capsaicin patch reduced neuropathic pain, improved functional mobility, and quality of life among patients with spinal cord injury-associated focal neuropathic pain. The authors comment, “In a population with a high incidence of polypharmacy, often including multiple central nervous system depressants and a need for effective opioid alternatives to mitigate pain, [8% capsaicin patch] is an effective topical alternative without systemic side effects.”