Dermal Delivery of Niacinamide—In Vivo Studies

Dermal delivery of NIA was investigated in vivo in human subjects using confocal Raman spectroscopy (CRS) and tape stripping (TS).

• The vehicles investigated included propylene glycol (PG), Transcutol®P (TC), binary combinations of PG with oleic acid (OA) or linolenic acid (LA) and a ternary system comprising of TC, caprylic/capric triglyceride (CCT) and dimethyl isosorbide (DMI).
• For the CRS studies, higher area under curve (AUC) values for NIA were observed for the PG:LA binary system compared with PG, TC and TC:CCT:DMI (p < 0.05).
• A very good correlation was found between the in vitro cumulative permeation of NIA and the AUC values from Raman intensity depth profiles, with a Pearson correlation coefficient (R^2) of 0.84.
• In addition, an excellent correlation (R^2 = 0.97) was evident for the signal of the solvent PG and the active.
• CRS was also shown to discriminate between NIA in solution versus crystalline NIA.
• The findings confirm that CRS is emerging as a powerful approach for dermatopharmacokinetic studies of both actives and excipients in human