In vitro comparative evaluation of skin permeation and dermal retention of clobetasol 0.05% and salicylic acid 6% nano lotion and clobetasol 0.05% and salicylic acid 6% conventional lotion using excised swine skin and Franz diffusion cells

Abstract

Background: Topical formulations aim to deliver drugs locally while minimizing systemic exposure. This study compared the in vitro skin permeation and dermal retention of Clobetasol Propionate 0.05% and Salicylic Acid 6% Nano Lotion with a Conventional Lotion.

Methods: Excised full-thickness dorsal swine skin was mounted on Franz diffusion cells with a diffusion area of 1.36 cm². A 100 mg dose of each formulation was applied and receptor-fluid samples were collected over 12 hours. Both active ingredients were quantified using reverse-phase high-performance liquid chromatography (RP-HPLC) with UV detection. Permeation, surface residue and skin retention were assessed using mass-balance calculations.

Results: Salicylic Acid showed time-dependent permeation from both formulations. At 12 hours, cumulative permeation was 0.969 mg (16.16%) for the nano lotion and 0.270 mg (4.50%) for the conventional lotion, indicating approximately 3.6-fold greater permeation with the nano lotion. Skin retention was 83.08% and 71.81%, respectively, while surface residues were 0.763% and 23.68%. Clobetasol propionate remained below the receptor-phase detection limit for both formulations. However, skin retention was higher with the nano lotion (86%) than with the conventional lotion (50%).

Conclusions: The nano lotion demonstrated greater salicylic acid permeation, higher dermal retention of both active ingredients and lower surface residue than the conventional lotion. These findings suggest improved dermal delivery and skin localization under the tested in vitro conditions. Further studies are needed to confirm these findings and establish their clinical relevance.