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Markl D, Sauerwein J, Goodwin DJ, van den Ban S, Zeitler JA. Non-destructive Determination of Disintegration Time and Dissolution in Immediate Release Tablets by Terahertz Transmission Measurements. Pharm Res 2017; 34:1012-1022. [PMID: 28155076 PMCID: PMC5382185 DOI: 10.1007/s11095-017-2108-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 01/13/2017] [Indexed: 11/29/2022]
Abstract
PURPOSE The aim of this study was to establish the suitability of terahertz (THz) transmission measurements to accurately measure and predict the critical quality attributes of disintegration time and the amount of active pharmaceutical ingredient (API) dissolved after 15, 20 and 25 min for commercial tablets processed at production scale. METHODS Samples of 18 batches of biconvex tablets from a production-scale design of experiments study into exploring the design space of a commercial tablet manufacturing process were used. The tablet production involved the process steps of high-shear wet granulation, fluid-bed drying and subsequent compaction. The 18 batches were produced using a 4 factor split plot design to study the effects of process changes on the disintegration time. Non-destructive and contactless terahertz transmission measurements of the whole tablets without prior sample preparation were performed to measure the effective refractive index and absorption coefficient of 6 tablets per batch. RESULTS The disintegration time (R 2 = 0.86) and API dissolved after 15 min (R 2 = 0.96) linearly correlates with the effective refractive index, n eff, measured at terahertz frequencies. In contrast, no such correlation could be established from conventional hardness measurements. The magnitude of n eff represents the optical density of the sample and thus it reflects both changes in tablet porosity as well as granule density. For the absorption coefficient, α eff, we observed a better correlation with dissolution after 20 min (R 2 = 0.96) and a weaker correlation with disintegration (R 2 = 0.83) compared to n eff. CONCLUSION The measurements of n eff and α eff provide promising predictors for the disintegration and dissolution time of tablets. The high penetration power of terahertz radiation makes it possible to sample a significant volume proportion of a tablet without any prior sample preparation. Together with the short measurement time (seconds), the potential to measure content uniformity and the fact that the method requires no chemometric models this technology shows clear promise to be established as a process analyser to non-destructively predict critical quality attributes of tablets.
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Ridgway C, Bawuah P, Markl D, Zeitler JA, Ketolainen J, Peiponen KE, Gane P. On the role of API in determining porosity, pore structure and bulk modulus of the skeletal material in pharmaceutical tablets formed with MCC as sole excipient. Int J Pharm 2017; 526:321-331. [PMID: 28432018 DOI: 10.1016/j.ijpharm.2017.04.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 04/03/2017] [Accepted: 04/17/2017] [Indexed: 11/26/2022]
Abstract
The physical properties and mechanical integrity of pharmaceutical tablets are of major importance when loading with active pharmaceutical ingredient(s) (API) in order to ensure ease of processing, control of dosage and stability during transportation and handling prior to patient consumption. The interaction between API and excipient, acting as functional extender and binder, however, is little understood in this context. The API indomethacin is combined in this study with microcrystalline cellulose (MCC) at increasing loading levels. Tablets from the defined API/MCC ratios are made under conditions of controlled porosity and tablet thickness, resulting from different compression conditions, and thus compaction levels. Mercury intrusion porosimetry is used to establish the accessible pore volume, pore size distribution and, adopting the observed region of elastic intrusion-extrusion at high pressure, an elastic bulk modulus of the skeletal material is recorded. Porosity values are compared to previously published values derived from terahertz (THz) refractive index data obtained from exactly the same tablet sample sets. It is shown that the elastic bulk modulus is dependent on API wt% loading under constant tablet preparation conditions delivering equal dimensions and porosity. The findings are considered of novel value in respect to establishing consistency of tablet production and optimisation of physical properties.
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Chakraborty M, Ridgway C, Bawuah P, Markl D, Gane PAC, Ketolainen J, Zeitler JA, Peiponen KE. Optics-based compressibility parameter for pharmaceutical tablets obtained with the aid of the terahertz refractive index. Int J Pharm 2017; 525:85-91. [PMID: 28377315 DOI: 10.1016/j.ijpharm.2017.03.093] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 03/30/2017] [Accepted: 03/31/2017] [Indexed: 11/28/2022]
Abstract
The objective of this study is to propose a novel optical compressibility parameter for porous pharmaceutical tablets. This parameter is defined with the aid of the effective refractive index of a tablet that is obtained from non-destructive and contactless terahertz (THz) time-delay transmission measurement. The optical compressibility parameter of two training sets of pharmaceutical tablets with a priori known porosity and mass fraction of a drug was investigated. Both pharmaceutical sets were compressed with one of the most commonly used excipients, namely microcrystalline cellulose (MCC) and drug Indomethacin. The optical compressibility clearly correlates with the skeletal bulk modulus determined by mercury porosimetry and the recently proposed terahertz lumped structural parameter calculated from terahertz measurements. This lumped structural parameter can be used to analyse the pattern of arrangement of excipient and drug particles in porous pharmaceutical tablets. Therefore, we propose that the optical compressibility can serve as a quality parameter of a pharmaceutical tablet corresponding with the skeletal bulk modulus of the porous tablet, which is related to structural arrangement of the powder particles in the tablet.
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Lin H, Dong Y, Markl D, Williams BM, Zheng Y, Shen Y, Zeitler JA. Measurement of the Intertablet Coating Uniformity of a Pharmaceutical Pan Coating Process With Combined Terahertz and Optical Coherence Tomography In-Line Sensing. J Pharm Sci 2017; 106:1075-1084. [DOI: 10.1016/j.xphs.2016.12.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 11/29/2016] [Accepted: 12/02/2016] [Indexed: 10/20/2022]
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Axel Zeitler J, Rades T. Interdependence of Dosage Form Microstructure and Performance. Pharm Res 2017; 34:887-889. [PMID: 28299534 PMCID: PMC5382177 DOI: 10.1007/s11095-017-2137-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 02/27/2017] [Indexed: 11/17/2022]
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Markl D, Wang P, Ridgway C, Karttunen AP, Chakraborty M, Bawuah P, Pääkkönen P, Gane P, Ketolainen J, Peiponen KE, Zeitler JA. Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography. J Pharm Sci 2017; 106:1586-1595. [PMID: 28267446 DOI: 10.1016/j.xphs.2017.02.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 02/23/2017] [Accepted: 02/24/2017] [Indexed: 11/15/2022]
Abstract
Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography. Terahertz time-domain spectroscopy was used to derive the porosity using effective medium approximations, that is, the traditional and an anisotropic Bruggeman model. The anisotropic Bruggeman model yields the better correlation with the nominal porosity (R2 = 0.995) and it provided additional information about the shape and orientation of the pores within the powder compact. The spheroidal (ellipsoids of revolution) shaped pores have a preferred orientation perpendicular to the compaction direction causing an anisotropic behavior of the dielectric porous medium. The results from X-ray computed microtomography confirmed the nonspherical shape and the orientation of the pores, and it further revealed that the anisotropic behavior is mainly caused by the interparticle pores. The information from both techniques provides a detailed insight into the pore structure of pharmaceutical tablets. This is of great interest to study the impact of tablet microstructure on the disintegration and dissolution performance.
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Dong Y, Lin H, Abolghasemi V, Gan L, Zeitler JA, Shen YC. Investigating Intra-Tablet Coating Uniformity With Spectral-Domain Optical Coherence Tomography. J Pharm Sci 2017; 106:546-553. [DOI: 10.1016/j.xphs.2016.09.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 09/19/2016] [Accepted: 09/21/2016] [Indexed: 11/26/2022]
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Ruggiero MT, Sibik J, Erba A, Zeitler JA, Korter TM. Quantification of cation–anion interactions in crystalline monopotassium and monosodium glutamate salts. Phys Chem Chem Phys 2017; 19:28647-28652. [DOI: 10.1039/c7cp05544g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Specific anion–cation orbital interactions lead to the large structural and spectral differences observed in crystalline monosodium and monopotassium glutamates.
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Ruggiero MT, Krynski M, Kissi EO, Sibik J, Markl D, Tan NY, Arslanov D, van der Zande W, Redlich B, Korter TM, Grohganz H, Löbmann K, Rades T, Elliott SR, Zeitler JA. The significance of the amorphous potential energy landscape for dictating glassy dynamics and driving solid-state crystallisation. Phys Chem Chem Phys 2017; 19:30039-30047. [DOI: 10.1039/c7cp06664c] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We show clear evidence for a theory proposing that the shape and structure of the PES is the fundamental factor underlying the dynamics at temperatures below the glass transition.
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Ruggiero MT, Axel Zeitler J, Korter TM. Concomitant polymorphism and the martensitic-like transformation of an organic crystal. Phys Chem Chem Phys 2017; 19:28502-28506. [DOI: 10.1039/c7cp04666a] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Terahertz vibrational spectroscopy and solid-state density functional theory together reveal the true nature of a pseudo-continuous crystalline polymorphic phase transition.
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Ruggiero MT, Zeitler JA, Erba A. Intermolecular anharmonicity in molecular crystals: interplay between experimental low-frequency dynamics and quantum quasi-harmonic simulations of solid purine. Chem Commun (Camb) 2017; 53:3781-3784. [DOI: 10.1039/c7cc00509a] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combined experimental spectroscopic and theoretical quasi-harmonic investigation of intermolecular anharmonicity in crystalline purine.
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Ruggiero MT, Zeitler JA. Resolving the Origins of Crystalline Anharmonicity Using Terahertz Time-Domain Spectroscopy and ab Initio Simulations. J Phys Chem B 2016; 120:11733-11739. [PMID: 27766874 DOI: 10.1021/acs.jpcb.6b10248] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Anharmonicity has been shown to be an important piece of the fundamental framework that dictates numerous observable phenomena. In particular, anharmonicity is the driving force of vibrational relaxation processes, mechanisms that are integral to the proper function of numerous chemical processes. However, elucidating its origins has proven difficult due to experimental and theoretical challenges, specifically related to separating the anharmonic contributions from other unrelated effects. While no one technique is particularly suited for providing a complete picture of anharmonicity, by combining multiple complementary methods such a characterization can be made. In this study the role of individual atomic interactions on the anharmonic properties of crystalline purine, the building block of many DNA and RNA nucleobases, is studied by experimental terahertz time-domain spectroscopy and first-principles density functional theory (DFT) and ab initio molecular dynamics simulations (AIMD). In particular, the detailed vibrational information provided by the DFT calculations is used to interpret the atomic origins of anharmonic-related effects as determined by the AIMD calculations, which are in good agreement with the experimental data. The results highlight that anharmonicity is especially pronounced in the intermolecular interactions, particularly along the amine hydrogen bond coordinate, and yields valuable insight into what is similarly observed complex biosystems and crystalline solids.
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Ruggiero MT, Sibik J, Zeitler JA, Korter TM. Examination of l-Glutamic Acid Polymorphs by Solid-State Density Functional Theory and Terahertz Spectroscopy. J Phys Chem A 2016; 120:7490-5. [PMID: 27588684 DOI: 10.1021/acs.jpca.6b05702] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability of l-glutamic acid to crystallize in two different forms has long been the subject of study due to its commercial importance. While a solvent-mediated phase transformation between the α and β polymorphs is the prevailing theory, recent reports indicate a thermal solid-solid transformation between the two may be possible. However, determining accurate thermodynamic stabilities of these crystals has been challenging. Here new low-temperature single-crystal X-ray diffraction data coupled to solid-state density functional theory simulations have enabled a detailed description to be achieved for the energetic parameters governing the stabilization of the two l-glutamic acid solids. The temperature-dependent Gibbs free-energy curves show that α-glutamic acid is the preferred form at low temperatures (<222 K) and the β form is most stable at ambient temperatures. Terahertz time-domain spectroscopy was utilized to evaluate the quality of the intermolecular force modeling as well as to provide characteristic low-frequency spectral data that can be used for quantification of polymorph mixtures or crystal growth monitoring.
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Bawuah P, Tan N, Tweneboah SNA, Ervasti T, Axel Zeitler J, Ketolainen J, Peiponen KE. Terahertz study on porosity and mass fraction of active pharmaceutical ingredient of pharmaceutical tablets. Eur J Pharm Biopharm 2016; 105:122-33. [DOI: 10.1016/j.ejpb.2016.06.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 05/04/2016] [Accepted: 06/07/2016] [Indexed: 11/29/2022]
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Bawuah P, Ervasti T, Tan N, Zeitler JA, Ketolainen J, Peiponen KE. Noninvasive porosity measurement of biconvex tablets using terahertz pulses. Int J Pharm 2016; 509:439-443. [DOI: 10.1016/j.ijpharm.2016.06.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/07/2016] [Accepted: 06/07/2016] [Indexed: 11/25/2022]
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Nartowski KP, Malhotra D, Hawarden LE, Sibik J, Iuga D, Zeitler JA, Fábián L, Khimyak YZ. 19F NMR Spectroscopy as a Highly Sensitive Method for the Direct Monitoring of Confined Crystallization within Nanoporous Materials. Angew Chem Int Ed Engl 2016; 55:8904-8. [DOI: 10.1002/anie.201602936] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 05/05/2016] [Indexed: 11/09/2022]
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Nartowski KP, Malhotra D, Hawarden LE, Sibik J, Iuga D, Zeitler JA, Fábián L, Khimyak YZ. 19F NMR Spectroscopy as a Highly Sensitive Method for the Direct Monitoring of Confined Crystallization within Nanoporous Materials. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201602936] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Ruggiero MT, Sibik J, Orlando R, Zeitler JA, Korter TM. Measuring the Elasticity of Poly-l-Proline Helices with Terahertz Spectroscopy. Angew Chem Int Ed Engl 2016; 55:6877-81. [PMID: 27121300 PMCID: PMC4999051 DOI: 10.1002/anie.201602268] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 03/25/2016] [Indexed: 11/06/2022]
Abstract
The rigidity of poly-l-proline is an important contributor to the stability of many protein secondary structures, where it has been shown to strongly influence bulk flexibility. The experimental Young's moduli of two known poly-l-proline helical forms, right-handed all-cis (Form I) and left-handed all-trans (Form II), were determined in the crystalline state by using an approach that combines terahertz time-domain spectroscopy, X-ray diffraction, and solid-state density functional theory. Contrary to expectations, the helices were found to be considerably less rigid than many other natural and synthetic polymers, as well as differing greatly from each other, with Young's moduli of 4.9 and 9.6 GPa for Forms I and II, respectively.
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Ruggiero MT, Sibik J, Orlando R, Zeitler JA, Korter TM. Inside Cover: Measuring the Elasticity of Poly- l-Proline Helices with Terahertz Spectroscopy (Angew. Chem. Int. Ed. 24/2016). Angew Chem Int Ed Engl 2016. [DOI: 10.1002/anie.201603825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Ruggiero MT, Sibik J, Orlando R, Zeitler JA, Korter TM. Innentitelbild: Measuring the Elasticity of Poly- l-Proline Helices with Terahertz Spectroscopy (Angew. Chem. 24/2016). Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201603825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Sibik J, Zeitler JA. Direct measurement of molecular mobility and crystallisation of amorphous pharmaceuticals using terahertz spectroscopy. Adv Drug Deliv Rev 2016; 100:147-57. [PMID: 26772139 DOI: 10.1016/j.addr.2015.12.021] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 12/23/2015] [Accepted: 12/24/2015] [Indexed: 11/26/2022]
Abstract
Despite much effort in the area, no comprehensive understanding of the formation and behaviour of amorphous solids has yet been achieved. This severely limits the industrial application of such materials, including drug delivery where, in principle, amorphous solids have demonstrated their great usefulness in increasing the bioavailability of poorly aqueous soluble active pharmaceutical ingredients. Terahertz time-domain spectroscopy is a relatively novel analytical technique that can be used to measure the fast molecular dynamics of molecules with high accuracy in a non-contact and non-destructive fashion. Over the past decade a number of applications for the characterisation of amorphous drug molecules and formulations have been developed and it has been demonstrated how this technique can be used to determine the onset and strength in molecular mobility that underpins the crystallisation of amorphous drugs. In this review we provide an overview of the history, fundamentals and future perspective of pharmaceutical applications related to the terahertz dynamics of amorphous systems.
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Ruggiero MT, Sibik J, Orlando R, Zeitler JA, Korter TM. Measuring the Elasticity of Poly‐
l
‐Proline Helices with Terahertz Spectroscopy. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201602268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Alhijjaj M, Yassin S, Reading M, Zeitler JA, Belton P, Qi S. Characterization of Heterogeneity and Spatial Distribution of Phases in Complex Solid Dispersions by Thermal Analysis by Structural Characterization and X-ray Micro Computed Tomography. Pharm Res 2016; 34:971-989. [PMID: 27095354 PMCID: PMC5382188 DOI: 10.1007/s11095-016-1923-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/06/2016] [Indexed: 11/30/2022]
Abstract
PURPOSE This study investigated the effect of drug-excipient miscibility on the heterogeneity and spatial distribution of phase separation in pharmaceutical solid dispersions at a micron-scale using two novel and complementary characterization techniques, thermal analysis by structural characterization (TASC) and X-ray micro-computed tomography (XμCT) in conjunction with conventional characterization methods. METHOD Complex dispersions containing felodipine, TPGS, PEG and PEO were prepared using hot melt extrusion-injection moulding. The phase separation behavior of the samples was characterized using TASC and XμCT in conjunction with conventional thermal, microscopic and spectroscopic techniques. The in vitro drug release study was performed to demonstrate the impact of phase separation on dissolution of the dispersions. RESULTS The conventional characterization results indicated the phase separating nature of the carrier materials in the patches and the presence of crystalline drug in the patches with the highest drug loading (30% w/w). TASC and XμCT where used to provide insight into the spatial configuration of the separate phases. TASC enabled assessment of the increased heterogeneity of the dispersions with increasing the drug loading. XμCT allowed the visualization of the accumulation of phase separated (crystalline) drug clusters at the interface of air pockets in the patches with highest drug loading which led to poor dissolution performance. Semi-quantitative assessment of the phase separated drug clusters in the patches were attempted using XμCT. CONCLUSION TASC and XμCT can provide unique information regarding the phase separation behavior of solid dispersions which can be closely associated with important product quality indicators such as heterogeneity and microstructure.
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Gomez Sanz S, McMillan L, McGregor J, Zeitler JA, Al-Yassir N, Al-Khattaf S, Gladden LF. The enhancement of the catalytic performance of CrOx/Al2O3 catalysts for ethylbenzene dehydrogenation through tailored coke deposition. Catal Sci Technol 2016. [DOI: 10.1039/c5cy01157d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The origin and role of coke in ethylbenzene dehydrogenation over CrOx/Al2O3 has been studied. Ethylene is the main coke precursor; however coke from aromatic species is beneficial for styrene production.
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Wallace VP, Ferachou D, Ke P, Day K, Uddin S, Casas-Finet J, Van Der Walle CF, Falconer RJ, Zeitler JA. Modulation of the Hydration Water Around Monoclonal Antibodies on Addition of Excipients Detected by Terahertz Time-Domain Spectroscopy. J Pharm Sci 2015; 104:4025-4033. [DOI: 10.1002/jps.24630] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 07/25/2015] [Accepted: 08/04/2015] [Indexed: 12/25/2022]
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