Topical bioequivalence of acyclovir creams using dermal microdialysis in pigs: a new model to evaluate bioequivalence for topical formulations.

The aim was to evaluate the bioequivalence of topically applied Acyclovir (ACV) creams using dermal microdialysis (DMD) in a pig model. Three ACV creams (3%), ACV1, ACV2 and ACV3, were topically administrated on the dorsum of pigs, and the DMD sampling technique was used to continuously collect microdialysate. The concentration of ACV in microdialysate was measured by HPLC and the concentration-time profiles were used to calculate pharmacokinetic parameters. The results showed that 90% confidence interval (CI) of the ratio of AUC(0-4 h) of ACV2 and ACV3 was between 88.2 and 105.7%, which was within the acceptance range (80-125%). Ninety percent CI of the ratio of C(max) of ACV2 and ACV3 was between 87.4 and 124.4%, which was within the acceptance range (80-125%). These data indicate that ACV2 and ACV3 used in this study were bioequivalent. This study demonstrates that the pig model coupled with DMD sampling can potentially provide a cost-effective strategy to evaluate topical drug delivery and its associated pharmacokinetic studies.