Regional differences in the in vitro penetration of methylsalicylate through equine skin

Commercial formulations of non-steroidal anti-inflammatory drugs (NSAIDs) are developed for human use but the extent to which they will pass through equine skin is unknown. Skin was harvested from five Thoroughbred geldings from the thorax, groin and leg (dorsal metacarpal) regions and frozen (-20 degrees C) until required. Two grams of methylsalicylate (Mesa) gel was applied to defrosted full-thickness samples in diffusion cells and the penetration of Mesa and its active metabolite, salicylate (Sa), through skin samples were measured over 24 h. Significantly higher (