| 1. |
- Ahmed, Hamzah, et al.
(author)
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Relationship between mechanical properties and crystal structure in cocrystals and salt of paracetamol
- 2017
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In: Drug Development and Industrial Pharmacy. - : Taylor & Francis. - 0363-9045 .- 1520-5762. ; 43:1, s. 89-97
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Journal article (peer-reviewed)abstract
- Objectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol Form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to differential scanning solid-state characterization. The powders were sieved and 90-360 µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35-180 MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slips planed were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid > PRA-HCL ≈ PRA-OXA > BPY > PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA.
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| 2. |
- Shimpi, Manishkumar R., et al.
(author)
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Tadalafil-malonic acid cocrystal : Physicochemical characterization, pH-solubility and supersaturation studies
- 2018
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In: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 18:8, s. 4378-4387
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Journal article (peer-reviewed)abstract
- The purpose of this study was to enhance the solubility and dissolution of a poorly water-soluble drug, tadalafil (TDF), by cocrystal formation with malonic acid (MOA), to characterize the cocrystal structure, and to quantify the cocrystal solution behavior. The crystal structure revealed a 1:1 stoichiometry wherein the TDF molecules form a double layered structure through N–H…O=C interactions linked to a catemeric chain of MOA molecules via O-H…O hydrogen bonds. Cocrystal solubility advantage (SA defined as Scocrystal/Sdrug) or supersaturation index was determined from eutectic point measurements to be 102 to 129 in the pH range of 1 to 3. Cocrystal dissolution generated supersaturation levels (Cmax/Sdrug) of 30 in buffer and 120 in the presence of a nucleation inhibitor, HPMC. The amorphous form of TDF generated supersaturation 3 times lower than cocrystal in buffer, and not significantly different from cocrystal in the presence of HPMC. Thus, supersaturation index is a valuable metric for assessing the risk of cocrystal conversion during kinetic studies and for predicting conditions when the usage of a precipitation inhibitor may significantly increase cocrystal exposure levels.
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| 3. |
- Srivastava, Karnica, et al.
(author)
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Molecular structure, spectroscopic signature and reactivity analyses of paracetamol hydrochloride monohydrate salt using density functional theory calculations
- 2019
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In: CrystEngComm. - : Royal Society of Medicine Press. - 1466-8033 .- 1466-8033. ; 21:5, s. 857-865
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Journal article (peer-reviewed)abstract
- The aim of this study was to understand the role of the intermolecular hydrogen bond interactions present in paracetamol hydrochloride monohydrated salt. Paracetamol hydrochloride monohydrate salt (PRA-HCl) and paracetamol (form I) were investigated via vibrational (FT-IR and FT-Raman) spectroscopy and density functional theory (DFT) to gain insight into the hydrogen bond patterns present in these crystalline materials. Two different density functionals, wB97X-D and M062X, were used for the comparison of the results. The geometrical parameters of PRA-HCl and form I obtained using these functional were compared with the crystallographic data, which proved the existence of intra-molecular and intermolecular hydrogen bonds. The C10O2 group of form I forms an intramolecular hydrogen bond, while the O1–H18 group of PRA-HCl forms an intermolecular hydrogen bond with a chloride ion (Cl−), resulting in the elongation of the bond length and shift to a lower wavenumber for the O1–H18 group. To examine the potency of hydrogen bonding, quantum theory of atoms in molecules (QTAIM) calculations were performed and the results suggested that O1–H18⋯Cl22 is a strong intermolecular hydrogen bond. The chemical reactivity parameters reveal that the PRA-HCl and PRA-OXA cocrystals are more reactive and softer (low HOMO–LUMO energy gap) in comparison to paracetamol (form I).
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