The lateral spread of clobetasol 17-propionate in the stratum corneum in vivo.

Radiolabelled clobetasol 17-propionate in two different bases, propylene glycol (PG) and di-n-butyl adipate (BA), was applied to the backs of 10 normal male volunteers, and the application sites protected. After 8 h samples of stratum corneum (SC) were taken from the application site and an adjacent site, and the level of steroid measured. At the application site there were higher concentrations of the PG formulation at the deeper levels of the SC. At the adjacent sites there were higher concentrations of the BA formulation at the superficial levels. The mean radioactivity at the adjacent sites expressed as a percentage of that at the corresponding application sites (+/- SEM) was 7.8 +/- 5.3% for the BA formulation and 3.0 +/- 2.9% for the PG, (P = 0.0002). Total percentage of the applied dose in the skin adjacent to the application site was 11.7 +/- 6.3% for the BA formulation and 5.3 +/- 5.7% for the PG (P less than 0.0002). Clobetasol 17-propionate, therefore, moves laterally to a greater extent in BA than in PG.