An Investigation of the Influence of PEG 400 and PEG-6-Caprylic/Capric Glycerides on Dermal Delivery of Niacinamide

Polyethylene glycols (PEGs) and PEG derivatives are used in a range of cosmetic and pharmaceutical products. However, few studies have investigated the influence of PEGs and their related derivatives on skin permeation, especially when combined with other solvents. Previously, we reported niacinamide (NIA) skin permeation from a range of neat solvents including propylene glycol (PG), Transcutol(R) P (TC), dimethyl isosorbide (DMI), PEG 400 and PEG 600. In the present work, binary and ternary systems composed of PEGs or PEG derivatives combined with other solvents were investigated for skin delivery of NIA. In vitro finite dose studies were conducted (5 mu L/cm(2)) in porcine skin over 24 h. Higher skin permeation of NIA was observed for all vehicles compared to PEG 400. However, overall permeation for the binary and ternary systems was comparatively low compared with results for PG, TC and DMI. Interestingly, values for percentage skin retention of NIA for PEG 400:DMI and PEG 400:TC were significantly higher than values for DMI, TC and PG (p < 0.05). The findings suggest that PEG 400 may be a useful component of formulations for the delivery of actives to the skin rather than through the skin. Future studies will expand the range of vehicles investigated and also look at skin absorption and residence time of PEG 400 compared to other solvents.