Delivery platforms for oral drug administration

The oral route is the most patient-compliant and widely used due to characteristics such as self-administration, minimal invasiveness and ease of use. In addition, oral pharmaceutical products are more cost-effective. However, this route presents several challenges such as the harsh stomach environment with low pH, enzymatic activity and mechanical forces, the presence of a mucus layer, the tight junctions between enterocytes and the phenomenon of hepatic first-pass metabolism, which causes the active ingredient to be metabolized in the liver before reaching the systemic circulation. To overcome these challenges, drug carriers can be surface-decorated or coated with compounds capable of protecting the entrapped cargo, facilitating the crossing of biological barriers, controlling the release kinetics, surpassing the first-pass and targeting it to specific portions or sites of the gastrointestinal tract. Altogether, these features may improve therapeutic efficacy and reduce undesired side-effects. At the same time, a fine control of the physicochemical characteristics of the drug carriers such size and surface charge during their production process is crucial to govern their interaction with the biological barriers. Due to all these challenges and the need to perform toxicity tests of these new carriers, to date only a few oral nanoformulations are commercially available and most of them are based on pure drug nanoparticles. This chapter will overview a number of relevant strategies to develop oral drug delivery systems and discuss the main effects of their characteristics on their therapeutic outcome.