Extended Hildebrand solubility approach and the log linear solubility equation

Area of Science:

• Physical Chemistry
• Pharmaceutical Sciences
• Drug Solubility

Background:

• The log linear solubility equation (log S = log Sw + sigma f) is a key model in pharmaceutical sciences.
• Understanding drug solubility in mixed solvent systems is crucial for formulation development.

Purpose of the Study:

• To investigate the relationship between the log linear solubility equation and the extended Hildebrand solubility approach.
• To evaluate the applicability of the log linear model for predicting drug solubility in various cosolvent systems.

Main Methods:

• Derivation of the log linear model from the extended Hildebrand approach.
• Analysis of drug solubility data in water-cosolvent mixtures.
• Comparison of model predictions with experimental solubility data.

Main Results:

• The log linear equation provides a good linear fit for semipolar drugs in water-cosolvent mixtures.
• The model is most successful when the cosolvent's solubility parameter is significantly higher than the drug's.
• An interfacial model, linked to the log linear equation, effectively describes solubility in polar mixed solvents.

Conclusions:

• The log linear solubility equation is a valuable tool for predicting semipolar drug solubility in specific mixed solvent systems.
• The extended Hildebrand approach provides a foundational framework for the log linear model.
• The findings support the use of these models in optimizing drug formulations.