| 1. |
- Alhalaweh, Amjad, et al.
(författare)
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1:1 and 2:1 urea-succinic acid cocrystals : structural diversity, solution chemistry, and thermodynamic stability
- 2010
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:11, s. 4847-4855
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the crystal structures of 1:1 and 2:1 urea-succinic acid (U-SA) cocrystals and to investigate the role of solution chemistry in the formation and stability of different stoichiometric cocrystals. The structural diversity of other urea-dicarboxylic acid cocrystals is also discussed. The 1:1 U-SA cocrystal was stabilized by an acid-amide heterosynthon while acid-amide heterosynthons and amide-amide homosynthons stabilized the 2:1 cocrystals. The hydrogen bonding motifs in 1:1 and 2:1 U-SA cocrystals were consistent with other urea-dicarboxylic acid systems with similar stoichiometries. The 1:1 cocrystals were transformed to 2:1 cocrystals upon slurrying in various solvents at 25 °C. The phase solubility diagram was used to define the stability regions of different solid phases in 2-propanol at 25 °C. While no phase stability region for 1:1 cocrystal could be found, the stable regions for the 2:1 cocrystals and their pure components were defined by eutectic points. The solubility of the 2:1 cocrystals was dependent on the concentration of the ligand in the solution and explained by the solubility product and 1:1 solution complexation. The mathematical models predicting the solubility of the 2:1 cocrystals were evaluated and found to fit the experimental data
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| 2. |
- Alhalaweh, Amjad, et al.
(författare)
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Effects of polymer and surfactant on the dissolution and transformation profiles of cocrystals in aqueous media
- 2014
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 14:2, s. 643-648
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Tidskriftsartikel (refereegranskat)abstract
- Capturing solubility advantages of cocrystals is of great interest, and thus to understand the mechanism by which different excipients could maintain the supersaturation generated by cocrystals at the course of absorption in aqueous media is essential. To achieve this aim, the impact of different excipients on dissolution behavior of indomethacin-saccharin (IND-SAC) were monitored by measuring the concentrations of cocrystal components in the absence and presence of various concentration of excipients by HPLC, and solid phases were analyzed by differential scanning calorimetry after each experiment and the potential of Raman spectroscopy for monitoring phase transformations in situ was tested. No dissolution advantage was offered by cocrystals in the absence of any solution additive. The polymer and surfactant used in the study increased the solubility of IND but not SAC. This differential solubilization effect is believed to have stabilized the cocrystals for a relevant period for the absorption to take place. This could be attributed to either decreased gap between supersaturation and saturation of the drug or drug interaction with the additives. Understanding the effects of excipients type and concentration on the transformation profile is vital for designing enabling formulations for cocrystals. The eutectic constant may be useful in selecting excipients for stabilizing cocrystals.
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| 3. |
- Alhalaweh, Amjad, et al.
(författare)
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Formation of cocrystals by spray drying
- 2010
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Ingår i: Journal of Pharmacy and Pharmacology (JPP). - : Oxford University Press (OUP). - 0022-3573 .- 2042-7158. ; 62:10 - Special issue, s. 1332-1333
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Spray drying is a widely used technique for material processing and scale-up. The cocrystals formation by spray drying is studied. In contrast to solvent evaporation method, spray drying of stiochiometric solutions of incongruently saturating cocrystals had generated pure cocrystals. The formation phenomena in spray drying could be kinetically controlled or mediated by glassy state.
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| 4. |
- Alhalaweh, Amjad, et al.
(författare)
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Formation of cocrystals from stoichiometric solutions of incongruently saturating systems by spray drying
- 2010
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:8, s. 3302-3305
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Tidskriftsartikel (refereegranskat)abstract
- Spray drying is a well established technique for material processing and scale-up. This study investigated the formation of pharmaceutical cocrystals by spray drying. The cocrystal formation mechanisms in spray-drying and solution methods, based on triangular phase diagrams, are discussed. The solvent evaporation of stoichiometric solutions of incongruently saturating cocrystals resulted in a mixture of phases, as dictated by the thermodynamic phase diagram. In contrast, spray drying of similar solutions of incongruently saturating systems generated pure cocrystals. It is thus suggested that the formation of cocrystals by spray drying could be kinetically controlled and/or mediated by the glassy state of the material.
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| 5. |
- Alhalaweh, Amjad, et al.
(författare)
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pH-dependent solubility of indomethacin-saccharin and carbamazepine-saccharin cocrystals in aqueous media
- 2012
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Ingår i: Molecular Pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 9:9, s. 2605-2612
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Tidskriftsartikel (refereegranskat)abstract
- Cocrystals constitute an important class of pharmaceutical solids for their remarkable ability to modulate solubility and pH dependence of water insoluble drugs. Here we show how cocrystals of indomethacin-saccharin (IND-SAC) and carbamazepine-saccharin (CBZ-SAC) enhance solubility and impart a pH-sensitivity different from that of the drugs. IND-SAC exhibited solubilities 13 to 65 times higher than IND at pH values of 1 to 3, whereas CBZ-SAC exhibited a 2 to 10 times higher solubility than CBZ dihydrate. Cocrystal solubility dependence on pH predicted from mathematical models using cocrystal K(sp), and cocrystal component K(a) values, was in excellent agreement with experimental measurements. The cocrystal solubility increase relative to drug was predicted to reach a limiting value for a cocrystal with two acidic components. This limiting value is determined by the ionization constants of cocrystal components. Eutectic constants are shown to be meaningful indicators of cocrystal solubility and its pH dependence. The two contributions to solubility, cocrystal lattice and solvation, were evaluated by thermal and solubility determinations. The results show that solvation is the main barrier for the aqueous solubility of these drugs and their cocrystals, which are orders of magnitude higher than their lattice barriers. Cocrystal increase in solubility is thus a result of decreasing the solvation barrier compared to that of the drug. This work demonstrates the favorable properties of cocrystals and strategies that facilitate their meaningful characterization.
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| 6. |
- Alhalaweh, Amjad, et al.
(författare)
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Pharmaceutical cocrystals of nitrofurantoin : Screening, characterization and crystal structure analysis
- 2012
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033 .- 1466-8033. ; 14:15, s. 5078-5088
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to screen and prepare cocrystals of the poorly soluble drug nitrofurantoin (NTF) with the aim of increasing its solubility. Screening for cocrystals of NTF using 47 coformers was performed by high-throughput (HT) screening using liquid assisted grinding (LAG) methods. Raman spectroscopy and powder X-ray diffraction (PXRD) were used as the primary analytical tools to identify the new crystalline solid forms. Manual LAG and reaction crystallization (RC) experiments were carried out to confirm and scale-up the hits. Seven hits were confirmed to be cocrystals. The cocrystals were characterized by PXRD, Raman and IR spectroscopy, thermal analysis (DSC and TGA) and liquid-state NMR or elemental analysis. The solution stability of the scaled-up cocrystals in water was tested by slurrying the cocrystals at 25 °C for one week. NTF forms cocrystals with a 1:1 stoichiometric ratio with urea (1), 4-hydroxybenzoic acid (2), nicotinamide (3), citric acid (4), l-proline (5) and vanillic acid (6). In addition, NTF forms a 1:2 cocrystal with vanillin (7). All but one of the NTF cocrystals transformed (dissociated) in water, resulting in NTF hydrate crystalline material or NTF hydrate plus the coformer, which indicates that the transforming cocrystals have a higher solubility than the NTF hydrate under these conditions. The crystal structures of 1:1 NTF-citric acid (4) and 1:2 NTF-vanillin (7) were solved by single-crystal X-ray diffraction. The crystal structures of these two cocrystals were analyzed in terms of their supramolecular synthons.
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| 7. |
- Alhalaweh, Amjad, et al.
(författare)
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Preparation of Zolmitriptan-Chitosan microparticles by spray drying for nasal delivery
- 2009
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 38:3, s. 206-214
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to use spray drying to prepare mucoadhesive dry powders of the antimigraine drug, zolmitriptan, in combination with the natural polymer, chitosan, for nasal administration. The effect of type, molecular weight, and proportion of chitosan on the powder and particle characteristics was also studied. Solutions containing different proportions of chitosans were prepared and spray dried. The chemical stability and content of the drug were determined by HPLC. The morphology and size range of the microparticles were also determined. Solid-state analysis was undertaken using thermal methods (DSC/MDSC and TGA), powder X-ray diffraction (PXRD), and Fourier transform infra-red spectroscopy (FT-IR). The drug release profiles were investigated and the time required to reach maximum solution concentrations (Tmax) was used for comparison. The drug was chemically stable, with a 93-105% loading in the microparticles. The microparticles were spherical with a narrow size distribution, irrespective of the formulation. Phase separation was observed for formulations containing less than 90% (w/w) chitosan, irrespective of the type. In contrast, in the formulation containing 90% (w/w) chitosan, the drug was molecularly dispersed. FT-IR studies showed that the bands corresponding to intermolecular hydrogen bonding were broader and more diffuse when zolmitriptan was amorphous. The formation of a hydrogen bond between drug and chitosans was also observed. Tmax increased as the proportion of chitosan decreased, and was proportional to the molecular weight of the chitosan in the formulation containing 90% (w/w) chitosan. Spray drying is a suitable technique for making mucoadhesive dry powders of zolmitriptan and chitosan for nasal application. The dispersion and release of the drug was affected by the properties and composition of the chitosan.
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| 8. |
- Alhalaweh, Amjad, et al.
(författare)
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Solubility behavior and solution chemistry of indomethacin cocrystals in organic solvents
- 2011
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 11:9, s. 3923-3929
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of this study was to investigate the solubility behavior and solution chemistry of indomethacin-saccharin (IND-SAC) cocrystals in organic media. We also evaluated previously proposed models of cocrystal solubility in organic solvents. In addition, the solubility behavior of IND-SAC cocrystals was compared with that of indomethacin-nicotinamide (IND-NIC) cocrystals using the eutectic constant approach. Phase solubility diagrams of IND-SAC cocrystals in various solvents were generated and the transition concentrations, at which drug and cocrystals are in equilibrium with the solvents, were determined. The solubility of IND-SAC cocrystals was explained by the solubility product and solution complexation. The tested models were found to fit the experimental data and to adequately explain the solubility behavior of the cocrystals. The solution complexation of IND and SAC is negligible in ethyl acetate and low in methanol and ethanol. The IND-NIC cocrystals were more soluble than the IND-SAC cocrystals in all the solvents studied. The eutectic constants predicted both the solubility and the stability of the cocrystals. Understanding the solubility behavior and solution chemistry of cocrystals has important implications for the screening, scale-up, and formulation development of this solid form. Further, the determination of eutectic constants is a simple and resource sparing means of obtaining key information on cocrystal stability and solution behavior
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| 9. |
- Alhalaweh, Amjad, et al.
(författare)
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Surface thermodynamics of mucoadhesive dry powder formulation of zolmitriptan
- 2011
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Ingår i: AAPS PharmSciTech. - : Springer Science and Business Media LLC. - 1530-9932. ; 12:4, s. 1186-1192
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Tidskriftsartikel (refereegranskat)abstract
- Microparticle powders for nasal delivery were formulated to contain the model drug, zolmitriptan, and varying proportions of different polymers. The objective of the study was to investigate the effects of these formulative parameters on the surface chemistry of the spray-dried microparticles and their potential for adhesion to the tested substrates, porcine mucin, and nasal tissue. The polymers used were chitosans of varying ionization states and molecular weights and hydroxypropyl methyl cellulose. The surface energies of the surfaces of the microparticles were determined using contact angle measurements and the van Oss model. The theory of surface thermodynamics was applied to determine the theoretical potential for the different materials to adhere to the substrates. It was found that the drug or polymers alone, as well as the various formulations, were more likely to adhere to mucin than to nasal tissue. Further, there was a trend for higher molecular weight chitosans to adhere better to the substrates than lower molecular weight chitosans. Similarly, adhesion was improved for formulations with a higher content of polymers. These theoretical predictions may be compared with further experimental results and be of use in making informed decisions on the choice of formulations for future expensive bio-studies.
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| 10. |
- Alhalaweh, Amjad, et al.
(författare)
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Theophylline cocrystals prepared by spray drying : physicochemical properties and aerosolization performance
- 2013
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Ingår i: AAPS PharmSciTech. - : Springer Science and Business Media LLC. - 1530-9932. ; 14:1, s. 265-276
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work was to characterize theophylline (THF) cocrystals prepared by spray drying in terms of the physicochemical properties and inhalation performance when aerosolized from a dry powder inhaler. Cocrystals of theophylline with urea (THF-URE), saccharin (THF-SAC) and nicotinamide (THF-NIC) were prepared by spray drying. Milled THF and THF-SAC cocrystals were also used for comparison. The physical purity, particle size, particle morphology and surface energy of the materials were determined. The in vitro aerosol performance of the spray-dried cocrystals, drug-alone and a drug-carrier aerosol, was assessed. The spray-dried particles had different size distributions, morphologies and surface energies. The milled samples had higher surface energy than those prepared by spray drying. Good agreement was observed between multi-stage liquid impinger and next-generation impactor in terms of assessing spray-dried THF particles. The fine particle fractions of both formulations were similar for THF, but drug-alone formulations outperformed drug-carrier formulations for the THF cocrystals. The aerosolization performance of different THF cocrystals was within the following rank order as obtained from both drug-alone and drug-carrier formulations: THF-NIC > THF-URE > THF-SAC. It was proposed that micromeritic properties dominate over particle surface energy in terms of determining the aerosol performance of THF cocrystals. Spray drying could be a potential technique for preparing cocrystals with modified physical properties.
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