Counterirritants and sensory profiling of pain-relieving patches

Abstract

Introduction: Musculoskeletal pain is a common medical and socioeconomic problem worldwide. Treatment and management options most commonly include analgesics such as paracetamol, nonsteroidal anti-inflammatory drugs (NSAIDs), and topical over-the-counter (OTC) preparations. Patients often use OTC topical analgesics owing to the benefits shown by clinical studies for the treatment and management of musculoskeletal injuries and disorders. The aim of this study was (1) to review the background, current understanding, and therapeutic usefulness of topical counterirritants for the management of musculoskeletal pain (2) and to evaluate the sensorial characteristics of two prototype patches containing counterirritants, designed to manage pain relief by delivering a warming or cooling sensation. Methods: Detailed literature search was conducted in PubMed, Google Scholar, and Cochrane Library databases for this review. An expert sensory panel study comprising of ten trained sensory experts was conducted to evaluate the performance of prototype patches containing counterirritants for their sensory characteristics including overall sensation, cooling, warming, and tingling sensations, as well as functional parameters such as ease of application and removal, adhesive property, odor intensity, staining on clothes, residue or greasiness, and sweat/moistness on the skin after removal. Results: Topical analgesics containing counterirritants like capsaicin, menthol, and salicylates produce analgesia by activating and then desensitizing epidermal nociceptors. Literature searches provide evidence for their use in the management of musculoskeletal pain. The expert sensory panel study showed that the sensations elicited by the prototype counterirritant patches were predominantly cooling, tingling, and low and short warming in nature, with strong adhesion, ease of application and removal, no staining, little to no residue and grease on the skin, and low lingering odor of menthol. Conclusion: Literature search supports the use of counterirritants in the treatment of musculoskeletal pain like backache, strains, and sprains. In addition, the observations from the expert sensory panel study evaluating sensory and functional parameters of counterirritant patches showed that these patches provide predominantly cooling, tingling and low short lasting warming sensations with strong adhesion, no stain and little to no residue and grease. These results support their potential as a treatment modality with increased consumer acceptance, potentially increasing treatment adherence and maximizing the effectiveness of therapies. And may be used as part of multimodal pain treatment regimens for musculoskeletal conditions.