A novel foam vehicle for delivery of topical corticosteroids

Skin, particularly the uppermost layer--the stratum corneum--presents a formidable, largely impassable barrier to the entry of most compounds. Recently, a novel thermolabile, low-residue foam vehicle, VersaFoam (Connetics Corp, Palo Alto, Calif), has emerged that offers a number of clinical and cosmetic advantages for the delivery of therapeutic agents through the skin. Two corticosteroids--mid-potency betamethasone valerate and ultra-high-potency clobetasol propionate--are now available in this formulation, and other products are in development to deliver clindamycin and ketoconazole in the foam vehicle. A series of in vitro studies have demonstrated that the new foam has the ability to deliver the active drug at an increased rate compared with other vehicles. These findings suggest that the new foam utilizes a nontraditional "rapid-permeation" pathway for the delivery of drugs. It is likely that components within the foam (probably the alcohols) act as penetration enhancers, and reversibly alter the barrier properties of the outer stratum corneum, thus driving the delivered drug across the skin membrane via the intracellular route. This is in contrast to traditional topical delivery vehicles, which must first rely on hydration of the intercellular spaces in the stratum corneum to achieve drug delivery. The latter mechanism reflects a hydration-dependent process, which may result in comparatively slower drug permeation.