Transdermal delivery offers an attractive, noninvasive administration route but it is limited by the skin’s barrier
to penetration. Minimally invasive techniques, such as the use of microneedles (MNs), bypass the stratum corneum (SC)
barrier to permit the drug’s direct access to the viable epidermis. These novel micro devices have been developed to puncture
the skin for the transdermal delivery of hydrophilic drugs and macromolecules, including peptides, DNA and other
molecules, that would otherwise have difficulty passing the outermost layer of the skin, the SC. Using the tools of the microelectronics
industry, MNs have been fabricated with a range of sizes, shapes and materials. MNs have been shown to
be robust enough to penetrate the skin and dramatically increase the skin permeability of several drugs. Moreover, MNs
have reduced needle insertion pain and tissue trauma and provided controlled delivery across the skin. This review focuses
on the current state of the art in the transdermal delivery of drugs using various types of MNs and developments in the
field of microscale devices, as well as examples of their uses and clinical safety.
Keywords: Drug delivery, microneedles, safety, skin penetration enhancement, stratum corneum, transdermal delivery.
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