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Abstract
Two crystal forms of fostedil were characterized using X-ray diffraction patterns and infrared spectra. The melting points of polymorph I and II were 95.3 °C and 96.4 °C, respectively.
Solubility studies demonstrated that, of the two fostedil polymorphs, form II was slightly more soluble than form I. The free energy difference between two polymorphs was small (71.8 cal/mol at 37 °C). Both crystals melted at about 60 °C in water considerably below the melting points.
Compression of form II at a compression force of 500 - 1000 kg/cm2 induced polymorphic changes in the crystal. Similar changes also were produced through grinding. The effects of some diluents on the polymorphic transformation from form II into form I by grinding were also studied. Microcrystalline cellulose and corn starch showed a polymorphic transfomation-accelerating effects.
Form I is more suitable for the pharmaceutical preparation.