Physiologically based pharmacokinetics is a mathematical modeling methodology employed to quantitatively simulate the absorption, distribution, metabolism, and excretion (ADME) of substances within a biological organism. This approach constructs multi-compartment models based on known physiological parameters specific to the species or population (e.g., organ volumes, blood flow rates) and the physicochemical and biochemical properties of the substance (e.g., protein binding, metabolic rates). Its significance lies in providing a mechanistic framework for predicting systemic and tissue-specific concentration-time profiles, enabling extrapolation across different conditions, species, or populations, and informing rational drug development and chemical risk assessment.