Drug property improvement crystallization

An essential property required to obtain a physically stable suspension formulation is that the drag substance has a low solubility in the suspension vehicle. This applies to all types of suspension whether intended for oral, parenteral or inhalation delivery. Since most suspensions are aqueous, a low solubility in water is required to prevent drug dissolution and crystal growth on storage. Some drugs intended for intramuscular use are formulated as suspensions in oil (e.g. penicillin injections are formulated in sesame oil) to improve chemical stability via a reduction in solubility. 

There are some useful methods to improve the physical stability of a suspension, such as decreasing the salt concentration, addition of additives to regulate the osmolarity, as well as changes in excipient concentrations, unit operations in the process, origin and synthesis of the drug substance, polymorphic behavior of the drug substance crystals, and other particle characteristics. However, methods based on changes of the particle properties and the surfactants used are the most successful [43],... 

Pharmaceutical co-crystals, as an emerging class of pharmaceutical material, provide an alternative to the salt form for drug molecules without ionizable groups [19, 20]. The major goal is to achieve potential improvement of physical properties (e.g., enhanced dissolution rates, mechanical properties, avoidance of moisture sensitivity. 

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