Polymorphism and solubility

Let us now take a closer look at the theory relating polymorphism and solubility [46], Consider a drug that has two polymorphic forms, polymorph 1 and polymorph 2. If the subscripts 1 and 2 refer to the respective polymorphs, we can state their free energies as... 

Drug Solvent/Temperature Polymorphs and Solubilities Ratio Reference... 

The thermodynamic relationships examined in Chapter 1 involving polymorphism and solubility have been applied to the methylprednisolone system [13]. The solubilities of the two polymorphs of this steroid were determined at various temperatures in water, decyl alcohol, and dodecyl alcohol. Because the chemical potential and thermodynamic activity of the drug in the solid state and in each saturated solution are constant, the solubility ratios for the two forms (which can be found in Table 1) were found to be independent of the solvent. The enthalpy, entropy, and temperature of transition calculated from the data were 1600 cal/mol, 4.1 cal/K mol, and 118°C, respectively. 

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