Toward a solid microneedle patch for rapid and enhanced local analgesic action

Abstract Analgesic creams find widespread application as adjuncts for localized anesthesia prior to surgical procedures. Nevertheless, the onset of analgesic action is protracted due to the skin barrier's inherent characteristics, which necessitates prolonged intervals of patient and clinician waiting, consequently impinging upon patient compliance and clinician workflow efficiency. In this work, a biodegradable microneedles (MNs) patch was introduced to enhance the transdermal administration of lidocaine cream to achieve rapid analgesia through a minimally invasive and conveniently accessible modality. The polylactic acid (PLA) MNs were mass-produced using a simple hot-pressing method and served the purpose of creating microchannels across the skin’s surface for rapid absorption of lidocaine cream. Optical and electron microscopes were applied to meticulously scrutinize the morphology of the fabricated MNs, and the comprehensive penetration tests involving dynamometer, Optical Coherence Tomography (OCT) and animal skins demonstrated the robust mechanical strength of PLA MNs for successful transdermal penetration. The behavioral pain sensitivity tests on living rats revealed that the MNs-assisted lidocaine treatment expeditiously accelerated the onset of action and substantially enhanced the efficacy of localized anesthesia. Furthermore, different treatment protocols encompassing the sequence of drug application relative to MNs treatment, MNs dimensions, and the frequency of MNs insertions exhibited noteworthy influence on the resultant local anesthesia efficacy. Together these results demonstrated that the lidocaine cream followed by diverse PLA MNs treatments would be a promising strategy for rapid clinical local anesthesia with wide-ranging applications.