PSIII-28 - Evaluation of tissue and plasma meloxicam concentrations using a microneedle patch for drug delivery

Abstract: The objective of this study was to evaluate plasma and ear tissue meloxicam concentrations when the drug was delivered using two different formulations of a microneedle patch placed on the back of the ear. Nursing pigs (n = 10; body weight = 3.64 ± 0.32 kg) from 1 litter were assigned randomly to 1 of 2 treatment groups. Patches delivered 2.5 mg of meloxicam/kg of body weight to pigs regardless of formulation, with the differences in patches being based on type of polymer located on the microneedles and base of the patch. Treatment groups were: 1) pigs receiving a microneedle patch with collagen, polyvinyl alcohol (PVA), and meloxicam on the microneedles, with PVA and chitosan on the base (n = 6 pigs; Patch A); and 2) pigs receiving a microneedle patch with chitosan, PVA, and meloxicam on the microneedles, with collagen and PVA on the base (n = 4 pigs; Patch B). During the study, pigs remained in the crate with the sow and littermates. An Estrotect® Breeding Indicator strip was used to adhere the microneedle patch on the ear of the pigs. Blood was collected at study initiation prior to patch administration (0 hours) and 24 and 48 hours for plasma meloxicam analysis. To evaluate tissue meloxicam concentrations, 3 pigs that received Patch A and 2 pigs that received Patch B were humanely euthanized after blood collection and patch removal at 24 and 48 hours, with the entirety of the ear removed for analysis. Statistical analyses were performed using the MIXED procedure of SAS 9.4 (Cary, NC) to assess the effects of treatment, hour, and treatment × hour interaction. Statistical significance was determined at P ≤ 0.05, with tendencies at 0.05 < P ≤ 0.1. There were no differences (P = 0.83) between patch formulations for tissue meloxicam concentrations (Patch A = 6.55 ± 2.12 ng/mg; Patch B = 7.32 ± 2.60 ng/mg). Plasma concentrations were not detectable at any time point, but tissue concentrations of meloxicam were detectable for pigs that received either patch formulation at 24 (5.44 ± 2.37 ng/mg) and 48 hours (8.42 ± 2.37 ng/mg). There were no differences (P = 0.41) between patch formulations for tissue meloxicam concentrations at either timepoint, nor was there an interaction of patch formulation and hour (P = 0.73). It is unknown why the meloxicam did not diffuse from the ear tissue into the plasma; however, further studies will focus on applying the microneedle patch at different areas on the animal to allow for optimal diffusion through the skin and into blood circulation for pain mitigation in livestock animals.