Dermatopharmacokinetics of betamethasone 17-valerate: Influence of formulation viscosity and skin surface cleaning procedure

The objective was to compare the in vivo distribution profiles of betamethasone 17-valerate (BMV) across the stratum corneum (SC) following (a) delivery from gelled and un-gelled formulations, and (b) two different skin cleaning procedures at the end of the application period. BMV was dissolved in gelled and un-gelled vehicles comprising either medium chain triglycerides (MCT) or a brand microemulsion (ME). The BMV concentration was adjusted to 80% of saturation and applied to the forearms of healthy volunteers. After 2 h, the treated skin site was cleaned either with a dry paper towel or with an isopropyl alcohol swab, and the SC was then progressively removed by repeated adhesive tape-stripping. BMV distribution profiles across the SC showed reasonable reproducibility, and that delivery from the ME was significantly superior to that from MCT. Gelled vehicles were less efficiently removed from the skin surface by dry wiping than un-gelled formulations. Removing excess formulation more aggressively with isopropyl alcohol resulted in a lower apparent uptake of drug into the SC. Excess gelled formulation may be trapped in the skin 'furrows', and requires an efficient skin cleaning procedure to ensure its complete removal.