Microneedle based drug delivery system and advantages in ocular drug delivery

The stratum corneum of the skin or the sclera/cornea of the eye, the outermost layer of the skin and others has the principal barrier to topically-applied medications. Thus, many therapeutic agents are limited by their inability to reach the systemic circulation. Transdermal delivery of hydrophilic drugs and macromolecular agents of interest is problematic. Therefore, facilitation of drug penetration through this barrier may involve by-pass or reversible disruption of molecular architecture. Microneedles, when used to puncture skin, will by-pass the barrier and create transient aqueous transport pathways of micron dimensions and enhance the transdermal permeability. These micropores are orders of magnitude larger than molecular dimensions, and, therefore, should readily permit the transport of hydrophilic macromolecules. This microneedle based drug delivery system will useful for the eye treatments by avoiding drawbacks of topical administration of drug, multiple drug treatment and other dosage form intended in the eye. This review gives the details of history, various types of microneedles, drug delivery, fabrication methods, manufacturing, evaluation and, importantly, investigations of clinical safety of microneedles.