Solvent-Containing Closure Material Prevents Follicular Penetration of Caffeine and Fluorescein Sodium Salt on Porcine Ear Skin

The study investigated the effectiveness of solvent-containing nail varnish as a closure material to prevent follicular penetration of caffeine and fluorescein sodium salt on porcine ear skin. It was found that standard nail varnish provided secure follicular closure, while solvent-free varnish did not. Gentle application techniques maintained the integrity of the follicular closure, whereas rapid techniques compromised it. In areas completely covered by the varnish, no caffeine penetration was detected, and there was no significant difference in penetration in adjacent uncovered areas, indicating no lateral diffusion. The study concluded that standard nail varnish with gentle application effectively prevents follicular penetration for the tested substances, though results may not apply to all active pharmaceutical ingredients.