Studies and methodologies on vaginal drug permeation.

The vagina stands as an important alternative to the oral route for those systemic drugs that are poorly absorbed orally or are rapidly metabolized by the liver. Drug permeation through the vaginal tissue can be estimated by using in vitro, ex vivo and in vivo models. The latter ones, although more realistic, assume ethical and biological limitations due to animal handling. Therefore, in vitro and ex vivo models have been developed to predict drug absorption through the vagina while allowing for simultaneous toxicity and pathogenesis studies. This review focuses on available methodologies to study vaginal drug permeation discussing their advantages and drawbacks. The technical complexity, costs and the ethical issues of an available model, along with its accuracy and reproducibility will determine if it is valid and applicable. Therefore every model shall be evaluated, validated and standardized in order to allow for extrapolations and results presumption, and so improving vaginal drug research and stressing its benefits.