Influence of vehicles and penetration enhancers on anti-inflammatory effect of 18-β glycyrrhetinic acid: Kinetic modelling of drug release, in vivo and ex vivo experiments

Abstract

Topical formulations of 18-β glycyrrhetinic acid (18-β GA) were designed for use in relieving inflammatory and painful conditions of the skin. Formulations were containing penetration enhancers that differ in penetration enhancing mechanisms. Anti-inflammatory effects of formulations and effects of penetration enhancers on penetration and permeation of the drug through rat skin were investigated. The total amount of 18-β GA permeated from the base oil/water emulsion (53.19 ± 22.25 mcg/cm2) was approximately twice higher than the base oleaginous cream (29.17 ± 3.85 mcg/cm2) while there was no 18-β GA permeation from the base hydrogel formulation to the skin (p < 0.05). Incorporation of propylene glycol was generally found to increase 18-β GA permeation to the skin. The highest oedema inhibiting activity was achieved in the oil/water emulsion containing propylene glycol followed by the base oil/water emulsion without a penetration enhancer (p < 0.05). This result was consistent with the ex vivo study. Limonene and oleic acid were found to be insufficient in 18-β GA permeation to the skin.