BIOAVAILABILITY and ADMET

This article provides a comprehensive overview of the concepts of bioavailability and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) as fundamental parameters in drug discovery and development. It explains how bioavailability determines the fraction of a drug that reaches systemic circulation and how physicochemical, biological, and formulation factors influence it. The discussion extends to the ADMET framework, which governs a drug’s pharmacokinetic and toxicological fate in the body. Each parameter—absorption, distribution, metabolism, excretion, and toxicity—is described in relation to the mechanisms affecting drug efficacy and safety. The paper also emphasizes Lipinski’s Rule of Five and the Bioavailability Score (BAS) as computational indicators for assessing oral drug-likeness. Moreover, it highlights the role of modern in silico tools such as SwissADME, pkCSM, ADMETlab, admetSAR, PreADMET, and Molinspiration in predicting pharmacokinetic and toxicity properties efficiently. Through the integration of computational, experimental, and predictive approaches, ADMET studies have become essential for optimizing drug design, reducing clinical failures, and accelerating the development of effective and safe therapeutic agents.