Nonamorphism in Flufenamic Acid and a New Record for a Polymorphic Compound with Solved Structures

The unprecedented polymorphism of the non-steroidal anti-inflammatory
drug (NSAID) flufenamic acid (FFA) is described here. Nine polymorphs
were accessed through the use of polymer-induced heteronucleation
(PIHn) and solid–solid transformation at low temperature. Structural
elucidation of six of these forms, in addition to the two previously
known forms, makes FFA indisputably octamorphic. Although the structure
of at least one other form of FFA remains elusive, the occurrence
of most of these polymorphs under one crystallization condition through
PIHn illustrates that a fine interplay exists among the kinetic factors
that lead to phase selection in this NSAID.