Systemic drug delivery in pigs using biodegradable microneedle patches

Abstract

Transdermal microneedle systems offer a minimally invasive strategy for systemic drug delivery in veterinary medicine. In this study, biodegradable microneedle patches composed of polyvinyl alcohol, collagen, and chitosan were evaluated in pigs for the delivery of two model compounds, fluorescein isothiocyanate–dextran (FITC-dextran, 4 kDa) and flunixin meglumine (FLU). Patches were applied to the ear and neck to assess the influence of anatomical site on systemic absorption. FITC-dextran delivered via a single 50 mg patch on the neck achieved approximately 1.2–1.4-fold higher plasma concentrations than oral administration and ear-applied patches, demonstrating enhanced uptake from vascularized regions. FLU patches applied to the ear produced detectable plasma levels up to 72 h post-application, with a maximum concentration of ∼1.9 μg L⁻¹ at 24–48 h, indicating sustained systemic exposure and reinforcing the potential for long-acting therapy. No adverse tissue responses were observed at application sites, highlighting the safety and tolerability of the patches. Overall, these findings emphasize the importance of anatomical site selection, physicochemical properties, and biocompatibility in optimizing microneedle-mediated transdermal drug delivery for veterinary applications.