PerspectiveFeatureCan pharmaceutical co-crystals provide an opportunity to modify the biological properties of drugs?

- Co-crystallization can enhance the solubility and/or permeability of drugs.
- The positions of the FDA and EMA on pharmaceutical co-crystals are very different.
- Co-crystallization does not appear to affect the drugs pharmacological activity.
- Co-crystals and physical mixtures can show very different biological properties.

Poorly soluble and/or permeable molecules jeopardize the discovery and development of innovative medicines. Pharmaceutical co-crystals, formed by an active pharmaceutical substance (API) and a co-crystal former, can show enhanced dissolution and permeation values compared with those of the parent crystalline pure phases. It is currently assumed that co-crystallization with pharmaceutical excipients does not affect the pharmacological activity of an API or, indeed, might even improve physical properties such as solubility and permeability. However, as we highlight here, the biological behavior of co-crystals can differ drastically with respect to that of their parent physical mixtures.