title: Structure, Solubility and Stability of Orbifloxacin Crystal Forms: Hemihydrate versus Anhydrate.
abstract: Orbifloxacin (ORBI) is a widely used antimicrobial drug of the fluoroquinolone class. In the official pharmaceutical compendia the existence of polymorphism in this active pharmaceutical ingredient (API) is reported. No crystal structure has been reported for this API and as described in the literature, its solubility is very controversial. Considering that different solid forms of the same API may have different physicochemical properties, these different solubilities may have resulted from analyses inadvertently carried out on different polymorphs. The solubility is the most critical property because it can affect the bioavailability and may compromise the quality of a drug product. The crystalline structure of ORBI determined by SCXRD is reported here for the first time. The structural analysis reveals that the ORBI molecule is zwitterionic and hemihydrated. ORBI hemihydrated form was characterized by the following techniques: TG/DTA, FTIR-ATR, and PXRD. A second crystalline ORBI form is also reported: the ORBI anhydrous form was obtained by heating the hemihydrate. These ORBI solid forms were isomorphous, since no significant change in unit cell and space group symmetry were observed. The solid-state phase transformation between these forms is discussed and the equilibrium solubility data were examined in order to check the impact of the differences observed in their crystalline structures.
authors.affiliation: Institute of Chemistry, Federal University of Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. olimpia_martins@yahoo.com.br.|Faculty of Pharmaceutical Sciences, Federal University of Alfenas; Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. olimpia_martins@yahoo.com.br.
authors.forename: Olimpia Maria Martins
authors.initials: OM
authors.lastname: Santos
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas; Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. jennifer_jacon@yahoo.com.br.
authors.forename: Jennifer Tavares Jacon
authors.initials: JT
authors.lastname: Freitas
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas; Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. crislaignier@yahoo.com.br.|Faculty of Pharmacy, Federal University of Bahia, Campus Ondina, Rua Barão de Jeremoabo, 147, Ondina, Salvador-BA 40170-115, Brazil. crislaignier@yahoo.com.br.
authors.forename: Edith Cristina Laignier
authors.initials: EC
authors.lastname: Cazedey
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas; Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. magali@unifal-mg.edu.br.
authors.forename: Magali Benjamim
authors.initials: MB
authors.lastname: de Araújo
authors.affiliation: Institute of Chemistry, Federal University of Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas-MG 37130-000, Brazil. doriguetto@unifal-mg.edu.br.
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Doriguetto
mesh_terms: D001682:Biological Availability; D002626:Chemistry, Pharmaceutical; D002939:Ciprofloxacin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000627:therapeutic use; D003460:Crystallization; D024841:Fluoroquinolones / Q000737:chemistry* / Q000627:therapeutic use; D015394:Molecular Structure; D012995:Solubility; D014867:Water / Q000737:chemistry*
chemical_list: D024841:Fluoroquinolones; D014867:Water; D002939:Ciprofloxacin; C095163:orbifloxacin
keywords: crystalline structure; orbifloxacin; solubility; stability