THE PERCUTANEOUS-ABSORPTION OF HYDROQUINONE (HQ) THROUGH RAT AND HUMAN SKIN IN-VITRO

Because of the potential for human contact with photographic developer solutions containing hydroquinone (HQ), the rates of percutaneous absorption of HQ through human stratum corneum and full-thickness rat skin have been measured in vitro using 5% aqueous solutions of HQ as the donor solutions. The studies were performed using infinite doses of aqueous solutions containing C-14-labeled HQ;in Franz-type diffusion cells. The measured absorption rate (mean +/- S.D.) of HQ through human stratum corneum was 0.52 +/- 0.13 mu g/cm(2)/h, while that for full-thickness rat skin was 1.1 +/- 0.65 mu g/cm(2)m. The ratio (ratmuman) of the permeability constants (K-p) was 2.4. Using the definitions suggested by Marzulli et al. (1969) Toxicol. Appl. Pharmacol. Suppl. 3, 76-83, HQ would be classified as 'slow' with respect to its absorption through human stratum corneum.