Chapter 8 - Microneedles

Abstract

This chapter focuses on microneedles (MNs). These are minute needles (usually less than 1000µm) that are used to make pores in the skin and enhance the transdermal delivery of medications into systemic circulation. An MN-based transdermal drug delivery approach combines the benefits of a traditional transdermal patch with injection-like drug transport. Considered as a hybrid between the transdermal patch and the hypodermic needle, MNs have transformed transdermal and intradermal drug delivery research. The obvious benefit of MNs is that they possess adequate length to cross the stratum corneum but are too short to stimulate nociceptors in the dermis. Besides painlessness and minimal invasiveness, the use of MNs can lead to improved patient compliance, increased drug bioavailability, the potential for self-vaccination, reduced risk of infection, and the ease of disposal. There are also several disadvantages associated with the utilization of MNs for drug delivery. Problems with dosing accuracy may be encountered as the drug may escape or may penetrate the skin at different rates if the device is not properly held. MNs also need to be administered with adequate force to avoid breaking or bending before insertion. Another disadvantage is that MNs can cause skin irritation and in some cases allergy. There are five classes of MNs: solid, hollow, hydrogel-forming, dissolving, and coated. Specific examples of the different types of MNs are discussed.