Predicting eutectic behavior of drugs and excipients by unique calculations

A eutectic is formed from a mixture of two or more solids and has a melting point lower than that of each of its constituents. It is generally represented by a phase diagram where the liquid and solid phases impact upon each other with a value known as the eutectic point. In pharmaceuticals, poor water solubility is a major obstacle for releasing new dosage forms into the market. Eutectic formation overcomes these problems. Preparation of a phase diagram by Differential Scanning Calorimetry can determine eutectic properties, but it is tedious. A modified Van’t Hoff (VH) equation was used in this study. Devalina Law developed a dimensionless index for the VH equation. The difference in melting points of an excipient polymer and drug are divided by the slope of the VH equation. In previous studies, five excipient–drug compositions were evaluated. The final index relationship was in good agreement except for the salt, quinine sulfate. In order to test the validity of the VH index, further studies of PEG with acetylsalicylic acid, acetaminophen, diflunisal, dimenhydrinate, ketoconazole, and mefenamic acid were performed.