In vivo imaging of drug delivery systems in the gastrointestinal tract.

An essential basis for the understanding of the complex interplay between oral drug delivery systems and gastrointestinal physiology is the ability to relate deposition of the dosage form to the plasma concentration time profile. The pharmaceutical scientist requires an array of methods that provide information on formulation disposition without influencing the physiological process, commonly termed "non-invasive" imaging modalities. In this paper, a short historical view on the suitability of different imaging modalities for the investigation of the fate of drug delivery systems in the GI tract is given. The focus of the review is the presentation of currently mostly used methodologies scintigraphy, magnetic tracking techniques like magnetic marker monitoring (MMM), magnetic moment imaging (MMI), AC biosusceptometry (ACB) and magnetic resonance imaging and the discussion of their strengths and weaknesses.