title: Structure and thermal stability of alprazolam and selected solvates.
abstract: Five forms of the drug alprazolam have been identified by thermal analysis and X-ray powder diffraction (XRD). The single crystal X-ray structures of two of these species, a polymorph 1 and a dihydrate 2, were determined. The dihydrate crystallized from a solution of alprazolam in methanol containing traces of water. Species 3 and 4 are nonstoichiometric solvates with ethanol and acetonitrile, respectively. The differential scanning calorimetric curves for the solvates 2-4 are similar, showing a desolvation endotherm, followed by an exotherm associated with recrystallization, and a final endotherm for the fusion of alprazolam. The solvates 3 and 4 were shown to be isomorphous by XRD. The products of desolvation of 2-4 were identified by their XRD traces. Solvates 2 and 3 yield polymorph 1 on desolvation, whereas solvate 4 yields a different polymorph.
authors.affiliation: Department of Chemistry, University of Cape Town, Western Cape, South Africa.
authors.forename: M R
authors.initials: MR
authors.lastname: Caira
authors.forename: B
authors.initials: B
authors.lastname: Easter
authors.forename: S
authors.initials: S
authors.lastname: Honiball
authors.forename: A
authors.initials: A
authors.lastname: Horne
authors.forename: L R
authors.initials: LR
authors.lastname: Nassimbeni
mesh_terms: D000525:Alprazolam / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray; D007536:Isomerism; D012995:Solubility; D012997:Solvents; D013816:Thermodynamics; D013818:Thermogravimetry
chemical_list: D012997:Solvents; D000525:Alprazolam