This review article by Robert G. Strickley focuses on the solubilizing excipients used in commercially available oral and injectable solution formulations. The excipients include water-soluble organic solvents, non-ionic surfactants, water-insoluble lipids, organic liquids/semi-solids, cyclodextrins, and phospholipids. The article highlights the importance of solubility and stability in formulation design, emphasizing that the chosen solvent system must be capable of solubilizing the drug at the desired concentration and maintaining chemical stability. The theory section explains the principles of solubility, including the free energy of solid and solution states, and the role of pH adjustment, cosolvents, complexation, microemulsions, self-emulsifying drug delivery systems, micelles, liposomes, and emulsions in enhancing solubility. The article also discusses the mathematical models used to describe these processes, such as the equations for solubility, chemical potential, and the solubility of weak acids and bases. The oral formulations section lists various solubilized oral formulations, including oral solutions, syrups, elixirs, and solutions filled into soft or hard capsules, and explains the reasons for using these formulations, such as enhancing bioavailability, providing a measurable dose, and accommodating patients who cannot swallow tablets or capsules.This review article by Robert G. Strickley focuses on the solubilizing excipients used in commercially available oral and injectable solution formulations. The excipients include water-soluble organic solvents, non-ionic surfactants, water-insoluble lipids, organic liquids/semi-solids, cyclodextrins, and phospholipids. The article highlights the importance of solubility and stability in formulation design, emphasizing that the chosen solvent system must be capable of solubilizing the drug at the desired concentration and maintaining chemical stability. The theory section explains the principles of solubility, including the free energy of solid and solution states, and the role of pH adjustment, cosolvents, complexation, microemulsions, self-emulsifying drug delivery systems, micelles, liposomes, and emulsions in enhancing solubility. The article also discusses the mathematical models used to describe these processes, such as the equations for solubility, chemical potential, and the solubility of weak acids and bases. The oral formulations section lists various solubilized oral formulations, including oral solutions, syrups, elixirs, and solutions filled into soft or hard capsules, and explains the reasons for using these formulations, such as enhancing bioavailability, providing a measurable dose, and accommodating patients who cannot swallow tablets or capsules.