Urea Complexes of Partially Fluorinated Esters¹

Adduction of amiloride hydrochloride in urea through a modified technique for the dissolution enhancement

“…11 The diffractogram of urea crystals also exhibits peaks corresponding to tetragonal form of urea, mainly characterized by the interplanar spacing at 4.04 Å . 39 In contrast, diffractogram of crystals of AHIC inclusion compounds show peaks at interplanar spacings at 4.21, 3.42, 3.61 and 7.28 Å , which are all characteristic of the hexagonal form of urea. 40,41 Absence of major peaks of AH (3.18, 3.86, 2.57 Å ) further substantiates the fact that the drug may be in an amorphous state.…”

Urea co-inclusion compounds of 13 cis-retinoic acid for simultaneous improvement of dissolution profile, photostability and safe handling characteristics

“…Pure cis-RA is crystalline, as demonstrated by the sharp and intense diffraction peaks. The diffractogram of urea crystals also depicts peaks characteristic of the tetragonal form of urea, mainly characterized by the peak at 22° 2q (interplanar spacing at 4.04Å) (Radell & Connolly 1960). However, the diffractogram of crystals of cRAIC shows peaks…”

Urea inclusion compounds of enalapril maleate for the improvement of pharmaceutical characteristics

“…Diffractional peaks relevant to crystalline enalapril maleate were not detectable in EMIC products, indicating that the guest molecules were trapped and isolated from one another in the honeycomb network of urea and do not contribute to the crystal structure except for slight distortions of the hexagonal channels caused by bulky guests (Radell & Connolly 1961). The diffractogram of hexagonal urea (EMIC; important peaks at interplanar spacings at 4.16 (19%), 3.39 (100%) and 7.36 (5%) Å) (Radell & Connolly 1960;Brodman & Radell 1967) was characteristically distinguishable from that of the pure tetragonal form of urea (mainly characterized by the interplanar spacing at 4.04 (100%) Å) (Radell et al 1964), indicating a change in the crystalline form of urea.…”