Formation and Solid-State Characterization of a Salt-Induced Metastable Polymorph of Flufenamic Acid

Using additives is one of more recent and special methods to obtain a desirable polymorph. However, for pharmaceuticals, additives are usually limited to structurally related organic compounds. In this study, we have shown the potential of using a salt additive to induce crystallization of the metastable polymorph V of flufenamic acid (FFA). Additionally, it was found that FFA V undergoes a rapid interface mediated polymorphic transformation. Therefore, the slow evaporation method which can decrease the contact of the solvent during crystallization was chosen to delay the polymorphic transformation. It can be concluded that understanding the system is a prerequisite for using additives to obtain the desired polymorph.