Functional Status of GI Mucosa and Oral Drug Absorption

The gastrointestinal (GI) tract is one of the most complex organs in the body. It represents a barrier between the external and internal milieu. The main functions of the GI system are digestion and absorption. It also protects against unwanted substances and microorganisms, while eliminating the excess of unnecessary substances from the body. Peroral drug administration is the preferred route of administration in pharmacotherapy treatment because it is inexpensive, convenient and safer for patients. Unlike the intravenous route of administration, the peroral route is limited by the absorption process. Absorption is determined by the functional characteristics of the mucous membranes of different GI regions and the drug-related factors. The GI mucosa lays the surface of the GI tract, forming a solid barrier to drug absorption. There are different ways of drug passage through complex GI membranes. Understanding all absorption key factors is crucial for drug design and presents new perspectives for better pharmacotherapeutic outcomes.