The Pharmaceutics and Compounding Laboratory
Factors Influencing
the Solubility of Drugs

Learning Objectives

Upon completion of this exercise, you should be able to:

  • Define solubility, miscibility, salting-in, salting-out, complex ion formation, dielectric constant, and pHp.
  • Identify factors that affect drug solubility.
  • Explain the effects of temperature, multiple solutes, pH, and solute/solvent polarities (dielectric constant) on drug solubility.
  • Describe the fundamental relationship between product formulation, drug solubility, and drug absorption, bioavailability, and therapeutic efficacy.
  • Describe two (2) approaches to optimizing drug solubility.
  • Determine the pHp of a weak acid or base for a given concentration.
  • Given necessary experimental data, calculate the dielectric constant needed to solubilize a compound.