In a well-designed salt/co-crystal screening process, the optimal salt/co-crystal is chosen quickly, based on parameters such as solubility, hygroscopicity, crystallinity, chemical stability and suitability for production.
The benefits of using salts and co-crystals are numerous, some of those are as follows:
Dedicated or combined salt and co-crystal programs are targeted to identify the best solid forms for further development based on the following criteria:
The basis for selection of possible counter ions or co-crystal formers are toxicological aspects, as defined in the FDA GRAS (generally accepted as safe) list but also the intended application. As for example daily dosage forms have different requirements on a counter ion/co-crystal former than drugs that are dosed once weekly.