Vesicular drug delivery systems for oral absorption enhancement

Oral administration is the most acceptable route of drug delivery at this stage due to its convenience, safety, and non-invasiveness. However, drugs given orally are exposed to a complex gastrointestinal environment, causing a tremendous challenge for their successful absorption into the circulation. Over the past decades, researchers have developed various novel pharmaceutical technologies to improve oral absorption, among which the vesicular drug delivery system (like liposomes, niosomes and transfersomes) has received extensive attention. Encouragingly, there have been several investigations confirming the improved effect of vesicular drug delivery systems on oral drug absorption. Nevertheless, the clinical translation of oral vesicular drug delivery systems has been less impressive than implied by the positive results, and few vesicular formulations for oral use have been marketed yet. Against this background, this article provides an overview of the current applications and challenges associated with the vesicular delivery systems available for oral drug delivery, specifically liposomes, niosomes, transfersomes, chitosomes and bilosomes. The composition, formation mechanism, drug delivery advantages and application cases of these carriers in oral drug delivery are summarized. The possible mechanisms by which vesicular carriers enhance oral drug absorption are analyzed in terms of the in vivo process of oral drugs. Further, the challenges that oral vesicular carriers now face, such as safety, undefined in vivo fate, and scale-up production, are summarized, while possible strategies to deal with them are indicated. By reviewing the aforementioned, it can facilitate a more comprehensive knowledge of vesicular systems that can be used for oral drug delivery, providing a theoretical basis and reference for the design of oral formulations.