Article révisé par les pairs
Résumé : The crystallization of the nootropic drug piracetam in spin-coated thin layers on silicon oxide surfaces was analyzed by optical microscopy, as well as powder and synchrotron grazing-incidence X-ray diffraction. We observed the crystal structure formed to depend on the concentration of the solution used in the preparation of the samples and identified either the polymorphic form I (for concentrations <0.015 mol·dm-3) or form II (for >0.147 mol·dm-3). Although significant dewetting of the materials occurred over time, the transformation of form I, which is metastable at room temperature, to the more thermodynamically stable forms II or III was not observed, even at the long-term (9 months). Even when subject to prolonged solvent-vapor annealing, dewetting but no alteration of the polymorphic form occurred. Our results suggest that the metastable piracetam form I is stabilized upon crystallization from solution in thin films, which might generally pave the way to stabilizing metastable forms of drugs of increased dissolution rate.