Drug Absorption

ALAN TALEVI; CAROLINA L. BELLERA

The ADME Encyclopedia. A Comprehensive Guide on Biopharmacy and Pharmacokinetics

Springer Nature

Lugar: Basignstoke; Año: 2022;

Drug absorption, i.e. the process by which (intact) drug molecules are transferred to the bloodstream or, more precisely, into the systemic circulation, is greatly influenced by the intrinsic physicochemical and biochemical properties of the drug, as well as several pharmaceutical and anatomophysiological factors. Only free drug molecules in solution can be absorbed. Depending on the drug, the route of administration and the characteristics of the dosage form, the kinetics of drug absorption will be governed by drug release / dissolution from the pharmaceutical vehicle, or by the transference across biological barriers. Drug absorption is the only ADME process that can be directly influenced by pharmaceutical formulation and dosage form manufacturing, at least considering conventional drug delivery systems. Noteworthy, by considering drug absorption as the transfer from the absorption site to systemic circulation (i.e. oxygenated blood leaving the left ventricle of the heart), pre-systemic phenomena such as first pass metabolism are considered constitutive of the absorption process. However, there is not universal agreement regarding when the absorption process culminates (arrival of the drug molecules at the vascular space that perfuses the absorption site or arrival at the systemic circulation).