Skin structures associated with percutaneous drug penetration differ by body site in Beagles.

Body site selection for topical drug application in dogs may matter due to differences in follicular density and dermal vascularity.

This exploratory study investigated skin morphological differences across body sites in Beagles to better understand factors influencing percutaneous drug penetration. Six Beagles were enrolled between November 2024 and March 2025, with skin samples collected from three locations: the dorsum, lateral trunk, and ventral abdomen. Histological evaluation assessed epidermal thickness, stratum corneum (SC) layer count, and dermal vessel density, while dermoscopic imaging quantified follicular ostia density. Results demonstrated that epidermal thickness and SC layer count were relatively uniform across all three body sites, with maximum mean differences of approximately 0.3 SC layers. In contrast, follicular ostia density varied substantially by location, being highest at the dorsum, intermediate at the lateral trunk, and lowest at the ventral abdomen. Dermal vessel density showed moderate variation, with the ventral abdomen exhibiting higher values compared to the dorsum and lateral trunk. These findings suggest that when applying topical or transdermal medications in dogs, epidermal thickness and SC layer number may not be the primary determinants of site-to-site variability in drug absorption. Instead, follicular ostia density and dermal vascularity—both of which showed meaningful anatomical variation—may play more significant roles in governing percutaneous penetration. The authors acknowledge that while these structural differences are compelling, their direct impact on drug pharmacokinetics remains hypothetical and warrants further pharmacological investigation. These insights may have practical implications for optimizing topical drug formulations and application sites in canine patients.

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