Cocrystal Concept

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2. Conception of Cocrystal 2.1 Definition of Cocrystal A cocrystal is a crystalline form consisting of two or more different molecules in the lattice. A more restrictive definition has been provided as following: in its pure form, a cocrystal is a crystal containing multiple components that are all in solid-state under ambient conditions. These components co-exist in a stoichiometric ratio of a target molecule or ion and a neutral molecular cocrystal former(s)12. The components of most cocrystals are solid organic compounds. Cocrystals do not include liquids and gases as coformers. It means that solvates and hydrates are not considered as cocrystals in supramolecular chemistry field. When heated up, cocrystals tend to be more stable…show more content…
The definition of cocrystal by FDA aims to regulate its manufacturing process. According to the guidance, a cocrystal consists of an active pharmaceutical ingredient (API) with a neutral guest compound (coformer) in the crystal lattice. The components of cocrystals are in a neutral state and the interactions between components are nonionic, which distinguishes cocrystals from salts. Pharmaceutical cocrystals possess a solid-state form with arrays different from APIs that required salt formation. Coformers are considered as excipients in terms of FDA definition. The interaction between API and its coformer(s) is designed to achieve higher performance of drug characteristics such as stability, bioavailability and patient acceptance. The coformers are not limited to small organic molecules. For example, excipients such as β-cyclodextrin are also regarded as coformers. The dissociation of API from its coformer should occur before reaching action site of API. Moreover, cocrystal form of an API should not be considered as a new API regardless of its potential modification of physical-chemical…show more content…
FDA suggests that API processed by cocrystallization should be treated as a drug product intermediate. This definition is regarded as a method to protect the original drug and prevent further intelligence-right related issues. There are researchers arguing that the definition of the cocrystal form is partly overlapped with that of salt, hydrate or solvate14. Moreover, the guideline provided by FDA may hinder the development of cocrystal in pharmaceutical industry. The debate has not been settled yet. However, the definition of cocrystal is clearly not consistent between academic and industry field. The discrepancy is not further discussed

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