A Textbook of Physical Pharmaceutics (Theory)

About Book

Physical Pharmaceutics I provides a comprehensive foundation in the physical and physicochemical principles that govern the development, formulation, stability, and performance of pharmaceutical dosage forms. The book integrates fundamental concepts of physical chemistry with their practical applications in pharmacy, enabling students to understand how physicochemical properties influence the design and quality of pharmaceutical formulations. The book begins with solubility, distribution phenomena, and buffer systems, covering solubility expressions, solute–solvent interactions, factors affecting solubility, partition coefficient, critical solution temperature, and the effect of pH on drug solubility. It also explains pharmaceutical and biological buffer systems, methods of pH determination, buffer equations, buffer capacity, buffer preparation, and indicators. The subsequent section focuses on interfacial phenomena, including surface and interfacial tension, surface free energy, spreading coefficient, surface-active agents, hydrophilic–lipophilic balance (HLB), detergency, adsorption, wetting, contact angle, and the electrical properties of interfaces. These concepts provide an essential understanding of the behavior of pharmaceutical ingredients at solid–liquid and liquid–liquid interfaces. The book further discusses colloidal and coarse dispersions, with detailed treatment of lyophilic, lyophobic, and association colloids, their optical, kinetic, and electrical properties, stability, peptization, and protective action. The principles of suspensions and emulsions are explained through sedimentation, Stokes’ law, flocculation, controlled flocculation, theories of emulsification and stabilization, and physical instability phenomena such as creaming, coalescence, breaking, and phase inversion. A dedicated section on rheology explains Newtonian and non-Newtonian flow, thixotropy, negative thixotropy, viscosity measurement, viscoelasticity, and psycho-rheology. The pharmaceutical applications of rheological principles are emphasized to demonstrate their importance in the formulation and evaluation of liquid, semisolid, and other dosage forms. The final section covers micromeritics, including particle size and size distribution, particle shape, surface area, powder flow properties, methods of measurement, and techniques for improving powder flow. Advanced powder flow characterization using powder flow testers is also discussed. Overall, the book connects theoretical physicochemical principles with pharmaceutical applications, making it a valuable resource for B.Pharm students. It provides the conceptual foundation required for understanding preformulation, dosage-form design, formulation development, drug stability, dissolution, drug delivery, and pharmaceutical manufacturing.