Morphological evaluation of the γ-polymorph of indomethacin

A study has been made of the polymorphic nature of crystals of the pharmaceutical indomethacin grown from a wide range of solvents and from the melt. In most solvents, growth at high supersaturations yielded either a 1:0.5 solvated form (approximately) or the α-polymorph. At low supersaturations the γ-polymorph was commonly produced. Solutions in MeOH and tBuOH yielded a 1:1 solvate. The morphology of the γ-form showed no variation with solvent type but changed with supersaturation in a manner consistent with a differential variation in growth rates of the faces. This lack of solvent influence was confirmed by the fact that a similar morphology resulted on growth from the melt. Morphology predictions were carried out for the γ-polymorph and these show good agreement with experimental observations.