Assessment of Formulation and Biopharmaceutical Aspects in The Development of Oral Lipid-Based Drug Delivery Systems

The Gastrointestinal tract is separated into two parts: upper and lower. The upper GI tract includes the oral cavity, pharynx, esophagus, stomach, and the initial part of the small intestine, known as the duodenum. The lower GI tract includes the rest of the small intestine (jejunum and ileum), as well as the large intestine segments: The cecum, colon, and rectum. The structure of the GI tract is similar in all segments. The lumen is enveloped by smooth muscle cells, covered by mucus, submucosa, and several muscle layers. The mucosal layer which lines the inner part of the GI tract consists of a layer of epithelial cells, lamina propria, and muscularis mucosae, which play significant roles in food/drug molecule transport and gastrointestinal immunity. A broad absorption area and a lengthy residence period give more possibilities for drug absorption, which is why drug absorption occurs mostly in the small intestine.  Further, between the three main parts of the small intestine (duodenum, jejunum, and ileum), the jejunum and ileum have a higher absorption capacity compared to the duodenum. The average segment length, pH, mucus thickness, drug residence time, and bacterial diversity/population in various segments are factors of the environmental parameters that affect drug integrity and absorption. This review outlines, factors influencing drug delivery, and discusses attributes to overcome using lipid-based systems