Aim: Calcitonin gene-related peptide (CGRP) is a potential mediator of neurogenic inflammation in eczema, psoriasis and rosacea, and also contributes to vasodilatation and oedema in complex regional pain disorder. We investigated the feasibility of administering CGRP and its antagonist CGRP8-37 by iontophoresis in human skin to characterise their vasoactive profiles.
Methods: Two doses of each peptide were administered by iontophoresis (5 and 10 min duration at 0.1 mA) to the forearm skin of 6 healthy young men. Skin blood flow responses over 25 min were assessed using laser Doppler imaging.
Results: Iontophoresis of CGRP caused a gradual change in blood flow, with no significant difference in response between each dose. The peak change in flow had a coefficient of variation of 21% to 36%, while the variability of the total cumulative response was much greater. Iontophoresis of CGRP8-37 for 5 min caused only a small, transient increase in skin blood flow, while 10 min iontophoresis resulted in a significant increase in blood flow.
Conclusion: CGRP and CGRP8-37 can be administered by iontophoresis to human skin. Further experiments are needed to determine the optimum duration of iontophoresis and period of measurement.