Drug Absorption Principles

Abstract

Pharmacokinetics describes drug absorption, distribution, metabolism, and excretion processes. Absorption is the rate and extent at which drugs reach the systemic circulation from the site of administration. Distribution of a drug includes all the processes that are involved from the time when the drug reaches the circulation to the time when it (or a metabolite of the drug) leaves the body. Metabolism involves all the biochemical processes that result in a chemical change to the drug compound including both the metabolism in the gut wall, the liver, and blood circulation. Excretion is the process in which the drug is eliminated from the systemic circulation into bile, urine, feces, sweat, and air (Allen, 1982). The reader is referred to authoritative texts in this area for a detailed review.