Development and Assessment of Acyclovir Gel Plaster Containing Sponge Spicules

Acyclovir is an acyclic purine nucleoside analog that is highly effective in inhibiting the herpes simplex virus. However, topical acyclovir has poor efficacy because of its low skin permeability. This study aimed to develop an acyclovir gel plaster containing sponge spicules (AGP-SS) to achieve synergistic improvements in skin absorption and deposition of acyclovir. The process of preparing the gel plaster was optimized by orthogonal experiments, while the composition of the formulation was optimized using the Plackett-Burman and Box-Behnken experimental designs. The selected formula was tested for physical properties, in vitro release, stability, ex vivo permeation, skin irritation, and pharmacokinetics. The optimized formulation exhibited good physical characteristics. In vitro release and ex vivo permeation studies showed that acyclovir release from AGP-SS was dominated by diffusion with significantly higher skin permeation (20.00 ± 1.07 μg/cm2) than that of the controls (p < 0.05). Dermatopharmacokinetic analyses revealed that the maximum concentration (78.74 ± 11.12 μg/g), area under the curve (1091.81 ± 29.05 μg/g/h) and relative bioavailability (197.12) of AGP-SS were higher than those of the controls. Therefore, gel plaster containing sponge spicules show potential for development as transdermal delivery systems to achieve higher skin absorption and deposition of acyclovir, especially in deep skin layers.