Optimizing topical antibiotic delivery in dogs: Tear film pharmacokinetics of moxifloxacin following pre-treatment with hyaluronic acid

PURPOSE: To evaluate the impact of pre-treatment with mucoadhesive polymers on tear film concentrations of topically administered moxifloxacin in dogs. METHODS: Eight healthy dogs were enrolled in a randomized paired-eye crossover study consisting of two sessions (7-day washout). Eyes received topical 0.5% moxifloxacin alone (control) or following pre-treatment with a mucoadhesive polymer applied 30 seconds earlier: either 0.2% hyaluronic acid (HA; Hylogel®) or 0.75% cross-linked hyaluronic acid (XHA; Oculenis®). Tear samples were collected using microcapillary tubes at baseline and predefined intervals up to 480 minutes, and moxifloxacin concentrations were quantified by UV-Vis spectrophotometry (293 nm). RESULTS: Total moxifloxacin exposure (AUC0-480) increased following pre-treatment with either HA formulation. The XHA produced a statistically significant 2.0-fold increase in mean AUC0-480 over control (47,929 vs. 24,417 µg·min/mL; P = 0.005). The HA group achieved a 1.8-fold increase in mean AUC0-480 (37,104 vs. 20,693 µg·min/mL), but this did not reach statistical significance (P = 0.154). In the XHA trial, a significant treatment effect (P = 0.012) and interaction (P = 0.002) were observed for concentration, which remained significantly higher than control for 15 minutes (P ≤ 0.018). In the HA trial, a significant treatment effect was noted for concentration (P = 0.020), with levels remaining significantly higher than control for 10 minutes (P ≤ 0.024). No ocular irritation was observed. CONCLUSION: Prior administration of mucoadhesive polymers increases moxifloxacin bioavailability on the canine ocular surface, with this effect being more pronounced for cross-linked HA ("reservoir effect") compared to linear HA formulations. These findings may help optimize topical antibiotic delivery strategies in dogs with bacterial keratitis.