Enhancement of delivery and bioavailability for drugs and cosmecueticals using amphoteric surfactants1

Biologically active ingredients designed for topical use on skin require optimum delivery to the epidermis and dermis in order to promote healthy skin. The desired efficacy is related to the formulation which is dependant upon mode of action and drug chemistry together with the dynamics involved in penetration and subsequent delivery and bioavailability within the epidermal and dermal layers. Amphoteric surfactants in particular are a class of agents which offer the formulator a vehicle to elicit rapid drug availability at the required site of action. Amphoterics are unique in that they can bealtered via formulation to behave as negativelt charged cationics which can carry anionic drugs such as retinoic acid into the skin , or they can be formulated as negatively charged anionic moieties and thus enhance the delivery of cationic active drugs. The foregoing examples suggest a delivery mechanism similar to high density lipoprotein transfer inherant in skin physiology. Thus simple amino acids and polypeptides together with amine functional sterols, all of which carry positive charges and/or can accept a proton are likely to form similar complex delivery systems.In addition, certain amphoterics which exhibit a pronounced isoelectric point where both positive and negative moieties in the molecule are balanced can be used as nonionic delivery enhancers for drugs which are charge sensitive. The versatility of these compounds as described above should receive considerable attentionfrom formulators and pharmacologists alike in providing more efficacious bioavailable drug delivery systems. They are in addition also well tolerated by both the eye and skin mucosa.