Systemic circulation

Transdermal delivery holds a promising carrier in the transport of drugs to get direct access across the skin deep into the systemic circulation. It has attracted many researchers due to various biomedical advantages. The barrier nature of stratum corneum poses a threat to the drug delivery. Recently, the use of microneedles in increasing skin permeability has been proposed and shown to dramatically increase transdermal delivery, especially for macromolecules. In the microelectronics industry, microneedles have been fabricated with a range of sizes, shapes and materials. Most drug delivery studies have emphasized solid microneedles, which have been shown to increase skin permeability to a broad range of molecules and nanoparticles in vitro Microneedles can be used to enhance transdermal drug delivery. In this review different types of microneedles are described and their methods of fabrication highlighted. There are also hydrogel-forming microneedles. These are innovative microneedles which do not contain drugs but imbibe interstitial fluid to form continuous conduits between dermal microcirculation and an attached patch-type reservoir. Several microneedles approved by regulatory authorities for clinical use are also examined. It also focuses on the delivery of various therapeutic agents effectively different carriers emphasizing mainly on the potential role of microneedles as transdermal system.