In vitro and in vivo testing methods for respiratory drug delivery

Importance of the field: Successful respiratory drug delivery for local and systemic purposes is predicated on the availability of in vitro and in vivo methods for determining drug delivery and disposition following respiratory administration. Areas covered in this review: In this review, the relevance of new in vitro and in vivo methods for screening respiratory drug delivery is discussed. Specific topics covered include in vitro particle size characterization, in vitro dissolution test methods for respiratory formulations and in vitro respiratory absorption and disposition screening methods. Furthermore, in vivo respiratory dosing methods, in vivo respiratory aerosol deposition and drug absorption screening methods, and correlation between in vitro and in vivo methods are reviewed. What the reader will gain: After reading this article, the reader will have an enriched knowledge regarding the various in vitro and in vivo testing methods for respiratory drug delivery. Most importantly, this paper will make it possible for readers to appreciate the strengths and weaknesses of each test method, which in turn will assist them in selecting specific methods that suit their scientific needs. Take home message: New in vitro and in vivo methods for screening respiratory drug delivery are indispensible, especially from the respiratory drug development and quality control perspective. Each method has unique advantages and disadvantages that influence method selection and data interpretation. Although in vitro methods are used during drug development, they augment rather than substitute in vivo methods.