TOXIC EFFECTS OF CAPSAICIN ON KERATINOCYTES AND FIBROBLASTS

Pain management for partial-thickness burns and split-thickness skin g raft donor sites remains a persistent problem. Topical capsaicin (tran s-b-methyl-N-vanillyl-noneamide) has been successful for pain relief i n postherpetic neuralgia, arthritis, and diabetic neuropathy. It is th ought to work by inhibiting type C cutaneous factors and by releasing substance P, which is essential for wound healing. To evaluate the eff ects of topical capsaicin treatment on burn wounds and donor sites, an in vitro study was designed to consider cytotoxic effects of commerci al concentrations of capsaicin on keratinocytes and fibroblasts. Human keratinocytes and human fibroblasts were grown in tissue culture and exposed to varying concentrations of capsaicin (0.025% weight/volume t o 0.2% weight/volume). In addition, fibroblast-seeded collagen matrixe s were exposed to capsaicin to evaluate the compound's ability to caus e cytotoxic effects beneath the surface. Keratinocyte growth was reduc ed 21% to 31% in commercial concentrations of capsaicin 0.025% to 0.20 % weight/volume. Fibroblasts were reduced 5% to 10% during the first 6 hours of exposure to capsaicin and 30% after 24 hours across the full range of concentrations tested. At concentrations of at least 0.1% we ight/volume, capsaicin penetrated the collagen matrixes, resulting in fibroblast degeneration not only on the surface but also in the inner layers. On the basis of the fact that capsaicin was demonstrated to be cytotoxic to keratinocytes and fibroblasts and on the basis of its kn own detrimental effect on wound healing, it does not appear that topic al capsaicin is indicated for the treatment of burns.