FACTORS AFFECTING ORAL DRUG ABSORPTION: A BIOPHARMACEUTIC PERSPECTIVE

The oral route of administration is the most common and popular method of drug dosing, yet it presents a highly complex process for systemic delivery. This review aims to explore the multifaceted kinetics and underlying principles governing oral drug absorption. Systemic absorption from the gastrointestinal (GI) tract depends on a crucial triad of variables: the physicochemical properties of the drug (such as aqueous solubility and pKa), the formulation or dosage form used, and the anatomical and physiological characteristics of the absorption site.[1] Key physiological processes—including GI transit time, gastric emptying, and presystemic first-pass metabolism—act as rate-limiting steps that dictate whether absorption is dissolution-rate limited or permeability limited.[2] Additionally, variables at the absorption site can cause significant interpatient and intrapatient differences in the rate and extent of absorption. Ultimately, this variability can be minimized through the proper biopharmaceutical design of dosage forms, ensuring predictable bioavailability and reliable therapeutic outcomes in clinical settings.[1]