Topic overview

Start with the big picture

The lesson introduces partition coefficient (P) and logP, then connects lipophilicity with passive diffusion across biological barriers. It explains why absorption depends on balance: low logP can constrain permeability, while very high logP can compromise aqueous solubility and make bioavailability less predictable. The topic also distinguishes logP from logD, which accounts for ionization at a specified pH, and relates the unionized fraction of weak acids and bases to lipid partitioning. Further sections consider implications for drug distribution and formulation, including prodrug approaches, and outline common methods for determining logP. Together, these concepts provide a framework for understanding how partition behavior informs drug absorption and pharmaceutical evaluation.