The effects of formulation on the penetration and retention of budesonide in canine skin in vitro

This study investigated the effects of formulation on the penetration and retention kinetics of budesonide through canine skin in vitro. Full thickness, thoracic, dog skin was mounted in Franz-type diffusion cells and randomly assigned to receive one of three 0.025% (0.25 mg/mL) budesonide-containing formulations: Barazone (BZ, a novel formulation), isopropyl myristate (IPM) or propylene glycol (PG). At regular intervals over 84 h, the amount of budesonide penetrating or retained within the skin was quantified using high performance liquid chromatography. The restricted (or residual) maximum likelihood mixed model predicted that the flux of budesonide from BZ was 9.2-fold (P < 0.001) and 105-fold (P < 0.001) greater than from IPM and PG, respectively. Similarly, the skin retention of budesonide from BZ was more than 3-fold (P < 0.0001) and nearly 6-fold (P < 0.0001) greater than from IPM and PG, respectively. This study has demonstrated that the formulation can greatly affect the skin penetration and retention of budesonide in dogs, and consequently could be selected to maximise drug concentration and retention at the site of action. This has the potential to improve the efficacy and safety of, and owner compliance with, topical glucocorticoid therapy in dogs.