EVALUATION FOR INTRINSIC SKIN PERMEATION OF UNSTABLE COMPOUNDS

An evaluation method is proposed for the intrinsic skin permeation rat e of unstable compounds. Vitamin C and vitamin E were used as the mode l compounds, The degradation of vitamin C and E in the solutions follo wed first-order kinetics with degradation constants of 0.26 h(-1) and 0.014 h(-1), respectively, The apparent skin permeation profiles of vi tamin C and E in vitro, approximated by a nonlinear profile of the pol ynomial regression method, was corrected for intrinsic permeation rate considering first-order degradation in the receptor solution. The int rinsic profiles evaluated agreed well with the ones determined from ra dio-labelled compounds, indicating the feasibility of the present anal ysis.