Modified Transdermal Technologies: Breaking the Barriers of Drug Permeation via the Skin
Transdermal drug technology specialists are continuing to search for new methods that can effectively and painlessly deliver larger molecules in therapeutic quantities to overcome the difficulties associated with the oral route, namely poor bioavailability due to hepatic metabolism (first pass) and the tendency to produce rapid blood level spikes (both high and low). Transdermal delivery can improve the therapeutic efficacy and safety of drugs by more precise (i.e., site-specific) way but spatial and temporal placement within the body is required to reduce both the size and number of doses necessary to achieve the objective of systemic medication through topical application to the intact skin surface. Modulation of formulation excipients and addition of chemical enhancers can increase drug flux but that is not sufficient to ensure delivery of pharmacologically effective concentration of drug therefore, several new active rate controlled TDDS technologies (electrically-based, structure-based, velocity-based, etc.) have been developed and commercialized for the transdermal delivery of ‘troublesome' drugs. This review article covers most of the new active transport technologies involved in enhancing the transdermal permeation into an effective DDS. In-depth analysis, formulation approaches, applications, advantages and disadvantages of these newer technologies are discussed.
Keywords: Transdermal drug delivery, microneedles, macroflux, iontophoresis, ultrasound, powderject, skin abrasion.
> Tropical Journal of Pharmaceutical Research Vol. 6 (1) 2007: pp. 633-644