The pH-Dependent Microspecies Dissociations in the Trade-Off of Solubility and Permeability of Vitamin B2 Eutectic Solids

The microspecies-specific physicochemical properties of eutectic solids of sparingly water-soluble micronutrient, Vitamin B₂ (Riboflavin), with a few representative BCS drugs, viz., Theophylline, Theobromine, Mesalamine, and Barbituric acid are established. The interplay of solubility and drug permeation behavior is experimentally determined for the eutectic solids, and properties are corroborated with the concomitant relative concentrations of pH-dependent microspecies of Riboflavin and the drugs. Partner drug candidates are selected from different quadrants of BCS classification to apprehend the influence of their solubility on the overall efficacy of the eutectic solids. The coexistence and inseparable ionic, neutral, and/or zwitterionic microspecies are spotted, and the pH-reliant isomer-specific inflection of physicochemical and pharmacokinetic properties in such multicomponent solid formulations is demonstrated.