Bioavailability evaluation of dermocorticoids using differential infrared thermography.

Introduction. Differential infrared thermography, proposed in this paper, i s a technique based on direct observations of infrared radiations emitted b y the skin. The evolution of cutaneous temperature caused by the applicatio n of dermocorticoids on healthy skin demonstrates their pharmaco-dynamic pr operties. Materials and methods. The cutaneous thermal image was recorded in real tim e. Image processing using subtraction function readily provided differentia l infrared thermographic analysis of the effects. Four activity classes of dermocorticoids had been applied on healthy skin. A test immediately carrie d out after dermocorticoid application on skin without occlusion and the cl assical skin blanching-test have been performed. Results. Temperature differences between the dermocorticoids were detected within the first three hours after the application on the skin without occl usion. The dermocorticoid class II cream formulation under study induced a decrease in temperature more pronounced than the others dermocorticoids. Th e skin-blanching effect was more noticeable for dermocorticoids class I and II and it was not detected for class IV. Discussion. Subtraction thermograms provide a means of differential imaging . Evolutive temperature differences subsequent to unique application withou t dermocorticoid occlusion are evidenced during a short duration (the first three hours). This may correspond to efficacy differences while classical tests of vasoconstriction analyse the cutaneous blanching induced after the 6th hour. Concerning the skin-blanching effect, results of this first inve stigation are not sufficient for a precise qualitative and quantitative int erpretation. The main interest of differential infrared thermography is to be quantitative, without contact, continuous in real time. Differential inf rared thermography is more sensitive than classical thermography. It allowe d an objective evolution survey for dermocorticoids.