Acute effect of topical minoxidil on digital blood flow in patients with Raynaud's phenomenon

Objective. Raynaud's phenomenon is a relatively common disorder for which highly effective, well tolerated treatment has yet to be developed. Minoxidil, a potent vasodilator which, on a single application to the scalp causes significant local cutaneous vasodilation, was selected for study in primary Raynaud's phenomenon. Methods. Ten subjects were enrolled in a randomized double blind, placebo controlled acute challenge crossover trial. Single applications of topical minoxidil 5% solution and placebo were made to each subject's fingers on 2 separate occasions, and measures of digital skin temperature, systolic blood pressure, and laser Doppler flow were obtained, before and after acute cold challenge. Results. Digital skin temperature, systolic blood pressure, and laser Doppler flow both before and after cold challenge were not improved by pretreatment with topical minoxidil 5% solution. Conclusion. In individuals with primary Raynaud's phenomenon, a single application of minoxidil 5% solution to the fingers is not effective in improving baseline digital blood flow or cold tolerance.