Optimised transdermal delivery of pravastatin

Abstract

Wiechers’ programme “Formulating for Efficacy” initiated a new strategy to optimise the oil phase of topical formulations in order to achieve optimal transdermal drug delivery. This new approach uses the “Delivery Gap Theory” on any active pharmaceutical ingredients (APIs) to test if it could enhance transdermal drug delivery. The aim of the study was to formulate six different semi-solid formulations (three creams and three emulgels) with 2% pravastatin as the API in order to investigate the “Delivery Gap Principle”, by determining which formulation would deliver pravastatin best to the target-site (system circulation). The three cream- and three emulgel formulations had different polarities, i.e. a formulation with polarity equal to that of the stratum corneum (optimised), a non-polar (lipophilic)- and a polar (hydrophilic) formulation. Franz cell diffusion studies were executed over 12 h and the optimised emulgel (2.578 μg/cm2) had the highest median amount per area obtained. Tape stripping followed the diffusion studies and in the stratum corneum-epidermis, the hydrophilic emulgel (1.448 μg/ml) contained the highest median pravastatin concentration and the epidermis-dermis the optimised emulgel (0.849 μg/ml) depicted the highest pravastatin concentration. During this study, it was observed that when both emulgel and cream formulations were compared; the emulgels enhanced the delivery of pravastatin more than the creams.