In vitro percutaneous penetration of topically applied capsaicin in relation to in vivo sensation responses

Capsaicin, the primary pungent element in several spices, elicits a variety of physiological effects which are due to neurogenic responses. The aim of the study was to explore the in vivo sensation responses of capsaicin and to compare the results with the in vitro percutaneous absorption of the sub stance. The overall objectives were to determining an in vitro-in vivo corr elation for capsaicin. Capsaicin was applied in a chamber on the volar fore arm of twelve volunteers and in a flow-through diffusion chamber on excised human epidermal membranes. Topical administration of capsaicin produced a complex cutaneous sensation that changed in intensity and quality as a func tion of time and was characterized by sting, prick, burn and pain. Percutan eous steady-state penetrations of capsaicin with a receptor fluid consistin g either of 4% bovine serum albumin in phosphate buffered saline or 50% eth anol in water were 28.2 +/- 2.7 and 29.6 +/- 2.9 mu g/cm(2) per h, respecti vely. The corresponding cumulative penetrated amounts of capsaicin after 30 min were 14.7 +/- 1.7 and 19.2 +/- 2.1 mu g/cm(2), respectively. The prese nt investigation indicates that there is a good correlation between in vivo physiological responses and in vitro percutaneous penetration of topically applied capsaicin. (C) 2000 Elsevier Science B.V. All rights reserved.