Crystal engineering of ionic cocrystals

Pharmaceutical cocrystals are long known but relatively understudied class of compounds. In the past decade there is heightened interest in pharmaceutical cocrystals to the point now they are in the advance stage of drug product development. In general, cocrystals can be classified into two categories: molecular cocrystals (MCCs) that comprise only neutral components in the crystal lattice (coformers); ionic cocrystals (ICCs), which consist at least a salt i.e. ionic compound. ICCs are recently emerging class of crystal forms for the new fundamental science in the context of crystal engineering and have been barely studied in the context of pharmaceutical science. Chapter 1 highlights a brief history of molecular cocrystals (MCCs) but focuses primarily upon advances in discovery, design and development of pharmaceutical cocrystals that have occurred since an earlier review published in 2004. Further two case studies that demonstrate how pharmaceutical cocrystals can improve the physicochemical properties and clinical performance of API’s are presented. Chapter 2 mainly focusses on history, the advantages, the diversity and case studies of ionic cocrystals to improve the physicochemical properties of API’s. Chapter 3 addresses the propensity to form chloride···carboxylic acid versus chloride···phenol hydrogen bonds (supramolecular heterosynthons) through a combination of Cambridge Structural Database (CSD) data mining and the structural characterization of 12 novel ICCs, including 4 hydrates containing carboxylic acids, phenol groups, and chloride anions. Chapter 4 highlights a crystal engineering approach for the preparation and characterization of ionic cocrystals (ICCs) of lithium chloride (LIC) and lithium bromide (LIB) with glucose (GLU); further demonstrated the physical stability and pharmacokinetic studies of lithium chloride-glucose (LICGLU) ICC compared to that of lithium chloride. Chapter 5 concludes by emphasizing the need to explore ionic cocrystals in terms of design and their relevance to pharmaceutical science.