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

Topical formulations of 18-beta glycyrrhetinic acid (18-beta 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-beta GA permeated from the base oil/water emulsion (53.19 +/- 22.25 mcg/cm(2) ) was approximately twice higher than the base oleaginous cream (29.17 +/- 3.85 mcg/cm(2)) while there was no 18-beta GA permeation from the base hydrogel formulation to the skin (p < 0.05). Incorporation of propylene glycol was generally found to increase 18-beta 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-beta GA permeation to the skin.