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 bioavailability of salicylic acid (SA) after repeated (14-day) topical application to subjects who presented normal, acnegenic, or photodamaged facial skin. To emulate exposure characteristics likely to be encountered by subjects in these two subpopulations, individuals presenting facial acne were treated with 2% SA in a hydroalcoholic vehicle, and volunteers with aged or photodamaged skin received a comparable topical dose of SA in a cream (moisturizer-like) vehicle. Plasma concentration-time profiles and cumulative urinary excretion of SA were measured after the last dose in subjects who had received 15 consecutive daily topical applications of 27 mg of SA or oral doses of 81 mg of acetylsalicylic acid (ASA). The rate and extent of percutaneous absorption of SA were not affected by facial skin condition. Faster rates of absorption (C-max) were obtained with a hydroalcoholic compared with a cream vehicle. Systemic SA exposures were at least five-fold higher with oral ASA than topical SA. Based on systemic salicylate concentrations resulting from ingestion of 81 mg of ASA, these results support that patients without gross skin disorders are at minimal risk of adverse systemic effects from routine use of topical products containing 2% SA.