α-Bisabolol, a possible safe penetration enhancer for dermal and transdermal therapeutics

Abstract

α-Bisabolol, an inflammatory-inhibiting sesquiterpene, was assessed for its ability to enhance transepidermal drug penetration, in vitro. Human skin samples pretreated with a 1:1 α-bisabolol-propylene glycol mixture were 17-fold more permeable to 5-fluorouracil (5-FU) and 73-fold more permeable to triamcinolone acetonide (TACA) with respect to untreated skin. Differential scanning calorimetry of treated stratum corneum samples showed a dramatic decrease in the lipid transition enthalpy, suggesting increased lipid fluidity. Determinations of drug distribution indicated that the stratum corneum-vehicle partition coefficient of 5-FU was unaffected by the enhancer. The solubility ratio of TACA between the enhancer and the vehicle was very low in comparison with the increase in skin permeability. Hence, for both drugs the enhanced penetration in the presence of a-bisabolol arose predominantly from an increase in their diffusivities across the modified skin barrier.