title: Pharmaceutical cocrystals of diflunisal and diclofenac with theophylline.
abstract: Pharmaceutical cocrystals of nonsteroidal anti-inflammatory drugs diflunisal (DIF) and diclofenac (DIC) with theophylline (THP) were obtained, and their crystal structures were determined. In both of the crystal structures, molecules form a hydrogen bonded supramolecular unit consisting of a centrosymmetric dimer of THP and two molecules of active pharmaceutical ingredient (API). Crystal lattice energy calculations showed that the packing energy gain of the [DIC + THP] cocrystal is derived mainly from the dispersion energy, which dominates the structures of the cocrystals. The enthalpies of cocrystal formation were estimated by solution calorimetry, and their thermal stability was studied by differential scanning calorimetry. The cocrystals showed an enhancement of apparent solubility compared to the corresponding pure APIs, while the intrinsic dissolution rates are comparable. Both cocrystals demonstrated physical stability upon storing at different relative humidity.
authors.affiliation: G.A. Krestov Institute of Solution Chemistry RAS , 153045, Ivanovo, Russia.
authors.forename: Artem O
authors.initials: AO
authors.lastname: Surov
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Voronin
authors.forename: Alex N
authors.initials: AN
authors.lastname: Manin
authors.forename: Nikolay G
authors.initials: NG
authors.lastname: Manin
authors.forename: Lyudmila G
authors.initials: LG
authors.lastname: Kuzmina
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Churakov
authors.forename: German L
authors.initials: GL
authors.lastname: Perlovich
mesh_terms: D002152:Calorimetry, Differential Scanning; D004008:Diclofenac / Q000737:chemistry*; D004061:Diflunisal / Q000737:chemistry*; D008958:Models, Molecular; D012995:Solubility; D013806:Theophylline / Q000737:chemistry*
chemical_list: D004008:Diclofenac; D004061:Diflunisal; D013806:Theophylline
keywords: crystal lattice energy; diclofenac; diflunisal; dissolution; enthalpy of formation; intrinsic dissolution rate; pharmaceutical cocrystals; theophylline