*1.2.2 Stability*

Stability has the great importance during the development of new chemical entity. For the evaluation parameters of pharmaceutical co-crystals, stability also plays an important role. A newly produced co-stability crystal is often tested under four conditions: relative humidity (RH) stress, temperature stress, chemical stability and solution stability. Because the amount of water in the co-crystals might cause quality degradation, the relative humidity stress is used to determine the ideal storage conditions for the product. During investigations involving the sorption and desorption of water, it was discovered that co-crystals performed better [37]. Thermal stress and chemical stability are relatively less studied areas about co-crystals properties. Very few reports were discovered, and the few research conducted demonstrated that thermal stress investigations can be a useful tool for learning more about physicochemical stability [38]. When creating these materials, it is critical to evaluate the co-crystals' chemical stability. According to Schultheiss and Newman, solubility stability is the capacity of the co-crystals' constituents to remain in solution and not rapidly crystallize. Solution stability is a crucial factor in the creation of new drugs. To understand how co-crystals behave in release media, stability tests are conducted in addition to solubility or dissolution experiments [39].
