PERCUTANEOUS-ABSORPTION OF SALICYLIC-ACID AFTER REPEATED (14-DAY) IN-VIVO ADMINISTRATION TO NORMAL, ACNEGENIC OR AGED HUMAN SKIN

The objective of the present work was to determine the relative bioava ilability of salicylic acid (SA) after repeated (14-day) topical appli cation to subjects who presented normal, acnegenic, or photodamaged fa cial skin. To emulate exposure characteristics likely to be encountere d by subjects in these two subpopulations, individuals presenting faci al acne were treated with 2% SA in a hydroalcoholic vehicle, and volun teers with aged or photodamaged skin received a comparable topical dos e of SA in a cream (moisturizer-like) vehicle. Plasma concentration-ti me profiles and cumulative urinary excretion of SA were measured after the last dose in subjects who had received 15 consecutive daily topic al applications of 27 mg of SA or oral doses of 81 mg of acetylsalicyl ic acid (ASA). The rate and extent of percutaneous absorption of SA we re not affected by facial skin condition. Faster rates of absorption ( C-max) were obtained with a hydroalcoholic compared with a cream vehic le. Systemic SA exposures were at least five-fold higher with oral ASA than topical SA. Based on systemic salicylate concentrations resultin g from ingestion of 81 mg of ASA, these results support that patients without gross skin disorders are at minimal risk of adverse systemic e ffects from routine use of topical products containing 2% SA.