Recent advances and perspectives of microneedles as transdermal delivery vehicles for analgesic medications

Microneedles (MNs) represent a cutting-edge and idea-inspiring way of transdermal drug delivery, which can not only be administered painlessly and minimally invasively but also avoid hepatic first-pass metabolism and gastrointestinal degradation. The technique has spurred both industrial and scientific curiosity, and it is reported that MNs are being exploited for disease treatment, biomarker diagnostics, medical cosmetology, and other applications. MNs have also been proposed for pain management due to their painless administration, high bioavailability, and quick onset time. This review introduced the basic principle of MNs as a transdermal delivery vehicle and the characteristics of different types of MNs. The emphasis was attached to the recent advances of MNs for transdermal delivery of analgesic medications including opioid analgesics, nonopioid analgesics and adjuvant analgesics for pain management. It is hoped that this paper will expand the influence of MNs delivering analgesic medications for pain management and promote their clinical applications.