Widely used in clinical and physiological research to measure renal plasma flow. It is efficiently secreted by the renal tubules with minimal reabsorption, making it ideal for assessing kidney function, particularly the effective renal plasma flow (ERPF). When injected intravenously, PAH clearance from the blood provides a reliable estimate of how well the kidneys are filtering and excreting substances. This application is crucial in diagnosing and monitoring renal diseases and evaluating drug effects on kidney function. Additionally, PAH has been used in studies involving organic anion transport mechanisms in the liver and kidneys, contributing to pharmacokinetic research.