Low-frequency ultrasound sonophoresis to increase the efficiency of topical steroids: a pilot randomized study of humans

Abstract

Topical steroids are efficient in vasoconstriction potential, which is linked to their anti-inflammatory activity. Low-frequency ultrasound (US) applied on the skin (sonophoresis) may enhance the transdermal transport of various steroids. We aimed to assess, in a simple, blinded, randomized controlled pilot study, the clinical efficiency of sonophoresis in increasing vasoconstriction by enhancing the transdermal penetration of topical steroids in human skin. The study took place in the Clinical Investigation Center of the University Hospital of Tours and involved healthy volunteers. Three circular zones were delimited on each of the subjects' forearms: zone 1 (right and left) received topical steroids with 1-h occlusion, zone 2 with 2-h occlusion, and zone 3 with massage. Forearms were randomized to first undergo US, using a 36 kHz probe, delivered in a pulsed mode (2s on/5s off), during 5 min, with a US intensity of 2.72 W/cm(2), or no US. We used betamethasone 17-valerate in cream form as the topical steroid. The primary outcome was difference between forearms in skin color (increased whiteness reflecting the intensity of vasoconstriction) measured by 2 scores: values obtained with a chromameter (the higher the value, the whiter the skin) and a clinical visual score. The measurements were taken by a dermatologist by blinded assessment. Fifteen subjects were included. Vasoconstriction was significantly higher with the topical steroid applied after US, especially in zone 2, than without US. Vasoconstriction was increased at 1, 2, 3, 4, and 6h (e.g., chromameter score 63.4 versus 65.2, p=0.017 at 4h) and disappeared at 24h. Moreover, 2-h occlusion gave higher vasoconstriction scores than did 1-h occlusion or massage alone, whether US was applied or not. The use of low-frequency US coupled with 2-h occlusion is a synergistic way to increase the efficiency of topical steroids by enhancing skin permeability.