Application of methyl methacrylate copolymers to the development of transdermal or loco-regional drug delivery systems

Introduction: Methyl methacrylate copolymers (Eudragit (R)) have been exploited to developtransdermal patches, medicated plasters (hereinafter patches) and, more recently, film-forming sprays, microsponges and nano-particles intended to be applied on the skin. Areas covered: The article reviews the information regarding the application of Eudragits in the design and development of these dosage forms focusing on the impact of formulative variables on the skin drug penetration and the patch adhesive properties. Expert opinion: Eudragits combined with a large amount of plasticizers are used to design the pressure-sensitive adhesives, specialized materials used in the patch development. They have to assure the drug skin penetration and the contact with the skin. Most of the studies mainly deal with the former aspect. The authors used a Eudragit type opportunely plasticized to merely investigate the in vitro or in vivo skin permeability of a loaded drug. However, the summa of these data evidenced that a strict connection between the matrix hydrophilicity and drug penetration probably exists. The criticisms of adhesion are addressed in a limited number of papers reporting data on technological properties, namely tack, shear adhesion and peel adhesion, while the structural data of the Eudragit adhesives, rheology and surface free energy are not described, excepting the case of Eudragit E. Among other applications, micro-and nanosystems exploiting the ionizable nature of some Eudragits can offer novel opportunities to develop pH-sensitive drug delivery systems suitable for triggering its release onto the skin.