The Organization of the Gut and the Oral Absorption of Drugs: Anatomical, Biological and Physiological Considerations in Oral Formulation Development

Abstract

Oral drug delivery remains the mainstay of patient treatment although the candidate drugs of the new millennium are becoming increasingly difficult to formulate for good systemic absorption. The area of oral delivery therefore represents an important area of innovation for pharmaceutical formulation including modulating solubility, exploiting windows of absorption and increasing bioavailability in a robust manner to attempt a more predictable outcome. In order to deliver an active pharmaceutical ingredient to facilitate systemic exposure, the drug must be presented in a dosage unit that contains an accurate dose of a specified active pharmaceutical ingredient which remains intact to the point of administration. On dosing, the pharmaceutical phase must be undone appropriately: the drug must be liberated at the correct rate, escaping degradation and metabolism and reach sufficient concentrations in the target tissue. The exposition of the pharmacist’s art is then completed in the lumen of the gut and therefore an understanding the organization of the organ system, at a macroscopic level, is of great relevance. In this chapter, the general integration of anatomy and motility with regard to the interaction of the dosage form will be considered. The biochemical and biophysical elements of absorption of the drug substance will not dealt with in detail in this chapter but by other books in this series.