THE CUTANEOUS CORTICOSTEROID VASOCONSTRICTION ASSAY - A REFLECTANCE SPECTROSCOPIC AND LASER-DOPPLER FLOWMETRIC STUDY

Cutaneous vasoconstriction induced by topical corticosteroids was investigated using non-invasive bioengineering techniques. Corticosteroids of different potency in alcoholic solution were applied topically, under occlusion, and cutaneous blanching was investigated using visual scoring, reflectance spectroscopy (RS) and laser-Doppler flowmetry (LDF). The RS technique allowed separation of cutaneous haemoglobin content into arterial oxygenated (OH) and venous deoxygenated haemoglobin (DOH) components. Application of alcohol decreased total haemoglobin by 10%, with a corresponding 8% increase in blood flow (BF). Clobetasol propionate was the most potent vasoconstrictor, inducing significant visible blanching and decreasing DOH (30%), OH (33%) and BF (18%) (P<0.01). Fluocinolone acetonide, betamethasone-17-valerate and dexamethasone also caused visible blanching (P<0.01). There was no significant decrease in BF, but reflectance spectroscopy showed a decrease in DOH (P<0.01). Tixocortol, CMJ and hydrocortisone acetate did not produce significant blanching, although DOH was decreased compared with the alcohol control. Measured by reflectance spectroscopy, corticosteroid-induced blanching was predominantly venoconstriction and only the most potent corticosteroid caused a significant decrease in OH and blood flow. This may explain why previous attempts to improve cutaneous vasoconstriction assays using laser-Doppler flowmetry have been unsuccessful.