title: Physicochemical properties of sildenafil citrate (Viagra) and sildenafil base.
abstract: Sildenafil citrate (Viagra) [I] and sildenafil base [II] are easily and unequivocally characterized by a set of physicochemical methods that include X-ray diffractometry, infrared spectroscopy, and thermal analysis. Monoclinic lattice constants: [I]: a = 26.98 A; b = 11.95 A; c = 16.68 A; beta = 106.97 degrees. [II]: a = 8.66 A; b = 34.27 A; c = 8.93 A; beta = 96.63 degrees. Both compounds decompose at 189.4 degrees C [I] and 251.9 degrees C [II]. Densities and refractive indices are given.
mesh_terms: D019343:Citric Acid / Q000737:chemistry; D004355:Drug Stability; D006361:Heating; D010879:Piperazines / Q000737:chemistry*; D011208:Powders; D011687:Purines; D000068677:Sildenafil Citrate; D013055:Spectrophotometry, Infrared; D013329:Structure-Activity Relationship; D013450:Sulfones; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D010879:Piperazines; D011208:Powders; D011687:Purines; D013450:Sulfones; D019343:Citric Acid; D000068677:Sildenafil Citrate