Stability of Pharmaceutical Co-Crystals Against Humidity Can Be Predicted

For the development of pharmaceutical products, the knowledge about their stability against relative humidity (RH) is crucial. Especially co-crystals (CC), composed from at least two components, present special challenges regarding physical stability at humid conditions. RH can lead to deliquescence and can induce dissociation and transformation to lesssoluble solid-state forms of the consisting components. We developed an approach for predicting the CC transformations that may happen upon CC storage at certain RHs. The new approach allows to reliably predict the deliquescence and transformation of CCs even in the presence of common excipients like sugars used in pharmaceutical formulations.