Effect of chemical enhancers on percutaneous absorption of daphnetin in isopropyl myristate vehicle across rat skin in vitro.

The percutaneous absorption properties of daphnetin with chemical penetration enhancers were investigated to explore the feasibility of daphnetin as a candidate for transdermal delivery to treat arthritis. Permeation experiments were carried out in vitro using 2-chamber diffusion cells in isopropyl myristate (IPM) vehicle using rat abdominal skin as a barrier. Various enhancers were employed, including O-acylmenthol derivatives synthesized in the laboratory and many conventional enhancers. Among the O-acylmenthol derivatives, 2-isopropyl-5-methylcyclohexyl 2-hydroxypanoate (M-LA) demonstrated a significant enhancing effect on daphnetin permeation. The highest degree of enhancement was obtained when NMP combined with Span 80 and the cumulative transport was 667.29 microg/cm(2) over 8 h. The solubility parameters, vehicle/stratum corneum partition, and diffusion coefficients were calculated to clarify the enhancing mechanism of classic enhancers on daphnetin. In conclusion, these findings allow a rational approach for designing an effective daphnetin transdermal delivery system.