Transdermal delivery

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.

Background: Honeybush extracts (Cyclopia spp.) can be incorporated into skin care products to treat conditions such as skin dryness and can function as an anti-oxidant.  Objective: To formulate Honeybush formulations and test it for antioxidant activity, skin penetration and skin hydrating effects.  Materials and Methods: Semi-solid formulations containing either Cyclopia maculata (2%) or Cyclopia genistoides (2%) underwent accelerated stability studies.  Membrane release studies, Franz cell skin diffusion and tape stripping studies were performed.  Antioxidant potential was determined with the TBA-assay and clinical efficacy studies were performed to determine the formulations’ effect on skin hydration, scaliness and smoothness after two weeks of treatment on the volar forearm.  Results: The formulations were unstable over three months.  Membrane release, skin diffusion studies and tape stripping showed that both formulations had inconclusive results due to extremely low concentrations mangiferin and hesperidin present in the Franz cell receptor compartments, stratum corneum-epidermis and epidermis-dermis layers of the skin.  Honeybush extracts showed antioxidant activity with concentrations above 0.6250 mg/ml when compared to the toxin; whereas mangiferin and hesperidin did not show any antioxidant activity on their own.  The semisolid formulations showed the potential to emit their own antioxidant activity.  Both formulations improved skin smoothness, although they did not improve skin hydration compared to the placebos.  Cyclopia maculata reduced the skin scaliness to a larger extent than the placebos and Cyclopia genistoides.  Conclusion: Honeybush formulations did not penetrate the skin but did however show antioxidant activity and the potential to be used to improve skin scaliness and smoothness.