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Otsuka, Makoto; Onoe, Mika; Matsuda, Yoshihisa

doi:10.1023/a:1018906320932

Cited by 34 publications

(22 citation statements)

References 7 publications

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“…The conventional analytical techniques frequently used for characterizing transition processes are powder X-ray diffraction (PXRD), [6] differential scanning calorimetry (DSC), [7] and Fourier transform infrared spectroscopy (FTIR). [8,9] These off-line techniques, however, usually require sample isolation and invasive preparation before the measurements, which may introduce error into the measured kinetic parameters.…”

Section: Introductionmentioning

confidence: 99%

In situ monitoring of solid‐state transition of p‐aminobenzoic acid polymorphs using Raman spectroscopy

Xia¹,

Wang²,

Ching³

2009

J Raman Spectroscopy

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The purpose of this study is to investigate the mechanism of solid-state polymorphic transition of p-aminobenzoic acid (PABA) using in situ Raman spectroscopy measurement. The polymorphic transition experiments were conducted on a micro quartz vessel mounted on a microscope, hot and cold stage, under isothermal conditions. The temperature was precisely controlled by a standalone temperature controller equipped with liquid nitrogen cooling system. The Raman spectroscopy probe was positioned on the surface of the solid sample in the micro vessel. The polymorphic transition progression was in situ monitored and recorded by Raman spectroscopy. Based on the polymorphic transition rate resulted from the quantitative analysis of Raman spectra, the mechanism of solid-state polymorphic transition of PABA was examined by various empirical kinetic models. An Arrhenius analysis was also performed to calculate activation energies from 134.7 kJ mol −1 to 137.7 kJ mol −1 for the transition. The results demonstrated that in situ Raman spectroscopy is a valuable and accurate technique to probe polymorphic transition process.

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Section: Introductionmentioning

confidence: 99%

In situ monitoring of solid‐state transition of p‐aminobenzoic acid polymorphs using Raman spectroscopy

Xia¹,

Wang²,

Ching³

2009

J Raman Spectroscopy

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“…In previous kinetic studies [43,44,46,47], on isothermal transitions of polymorphs, many samples of the starting crystalline material were stored, for each storage condition (temperature and RH), in a thermostat for various time intervals. In the case of extensive studies [46,47] including varying storage conditions, a large number of samples were subjected to quantitative analysis based on powder XRD or DSC, which makes such studies laborious.…”

Section: Validity Of Methodologymentioning

confidence: 99%

“…In the case of extensive studies [46,47] including varying storage conditions, a large number of samples were subjected to quantitative analysis based on powder XRD or DSC, which makes such studies laborious. The present study, using isothermal microcalorimetry, required only a single sample from start to finish for each storage condition, and the power evolved from the sample was automatically measured.…”

Section: Validity Of Methodologymentioning

confidence: 99%

“…Following this general procedure, polymorphic transitions of some pharmaceutical substances, e.g., seratrodast [43], acetazolamide [44], phenylbutazone [46] and phenobarbital [47] were successfully determined and kinetically analyzed. However, this conventional method is very troublesome because data are required at many time points, as fractions of conversion over the period of the reaction.…”

Section: Kinetics Of Polymorphic Transitionmentioning

confidence: 99%

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Characterization of Pharmaceutical Polymorphs by Isothermal Calorimetry

Urakami¹

2005

CPB

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A great number of pharmaceutical substances exist in crystalline solid-state. Because of the complexity of their chemical structure many different polymorphs of a given substance can exist. Polymorphic forms of solid pharmaceuticals influence not only their dissolution behavior, i.e. bioavailability but also their solid-state stability. It is well known that only one polymorphic form is thermodynamically stable and all other metastable forms will convert, eventually, to the more stable form. Hence it is essential to choose the most suitable polymorphic form in the early stage of pharmaceutical development. The following article reviews the recent applications of solution calorimetry that allows characterization of pharmaceutical polymorphs through accurate determination of enthalpy of solution. Each crystalline form possesses a defined enthalpy of solution, therefore solution calorimetry is used for the quantitative analysis of the desired polymorphic form and determination of enthalpy of transition corresponding to the difference in enthalpies of solution for a polymorphic pair. More recently this technique has been applied to the estimation of thermodynamic transition temperature, which is useful for the evaluation of thermodynamic stability relationships between polymorphs. This article will also describe the kinetics and thermodynamics of polymorphic transitions, from a metastable form to the thermodynamically stable form, through studies using ampoule-based isothermal microcalorimetry. Such studies are particularly useful when metastable forms are to be selected in order to enhance bioavailability. If the metastable form, or the pharmaceutical product containing it, can be shown to be sufficiently stable, it could then be used in a formulation where its therapeutic effects could be exploited.

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“…11) Recently, understanding the polymorphism has been positioned as an important research, since polymorphs and pseudopolymorphs show different physicochemical properties 7,8,[12][13][14][15][16][17][18] including solubility. 6) Generally, a stable polymorph shows low solubility and high stability, and metastable polymorphs exhibit higher solubility and lower stability.…”

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confidence: 99%

Physicochemical Characterization of Tamoxifen Citrate Pseudopolymorphs, Methanolate and Ethanolate

Kojima

Kato

Teraoka

et al. 2007

CHEMICAL & PHARMACEUTICAL BULLETIN

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During the development process of solid drugs, the most desirable crystal form should be appropriately selected based on the information of physicochemical properties including polymorphism, their salt 1,2) and co-crystal formation 3) of drug candidates, because physicochemical properties can affect efficacy, safety, 4-6) stability, 7,8) manufacturing process 9,10) and quality control. 11) Recently, understanding the polymorphism has been positioned as an important research, since polymorphs and pseudopolymorphs show different physicochemical properties 7,8,[12][13][14][15][16][17][18] including solubility. 6) Generally, a stable polymorph shows low solubility and high stability, and metastable polymorphs exhibit higher solubility and lower stability. From the viewpoint of the manufacturing process, information about organic solvates is also valuable for the selection of a crystallization solvent. Appropriate selection of the crystalline form from polymorphs and pseudopolymorphs should be conducted in order to achieve the purposes of development; this contributes to the improvement of stability, bioavailability and manufacturability.Tamoxifen, (Z )-2-[4-(1,2-diphenyl-1-butenyl)phenoxy]-N,N-dimethylethylamine, is one of the selective estrogen receptor modulators and tamoxifen citrate is widely used as a drug for the treatment of breast cancer. Tamoxifen has also been used as a model pharmaceutical compound for preformulation studies and several researches have been conducted.2,19-23) As for tamoxifen citrate (Fig. 1), two polymorphs, forms A and B, were identified. 24) Previously, we have investigated the photostability of forms A and B, and discussed the difference in photostability from the viewpoint of solid-state UV/Vis absorption spectroscopy.25) Even though tamoxifen citrate is widely used throughout the world, detailed characterization of its polymorphs and pseudopolymorphs has not been reported to the best of our knowledge.In this study, we prepared two novel pseudopolymorphs, methanolate and ethanolate, in addition to forms A and B reported previously. Their crystal forms were identified and characterized by powder and single crystal X-ray diffractometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy, scanning electron microscopy (SEM) and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), and their physicochemical stability was also evaluated. ExperimentalPreparation of Modifications Tamoxifen citrate was obtained from EGIS Pharmaceuticals (Budapest, Hungary). All solvents were purchased from Wako Pure Chemical Industries (Osaka, Japan). Form A was bulk powder purchased from EGIS Pharmaceuticals. A small amount of form A for SEM observation was obtained by recrystallizing from saturated acetonitrile solution of the drug by seeding a small amount of bulk powder. Form B was obtained by recrystallizing from saturated isopropyl alcoholic solution of the drug with stirring overnight at room temperature. Form B was then filtrated and dried i...

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Cited by 34 publications

References 7 publications

In situ monitoring of solid‐state transition of p‐aminobenzoic acid polymorphs using Raman spectroscopy

In situ monitoring of solid‐state transition of p‐aminobenzoic acid polymorphs using Raman spectroscopy

Characterization of Pharmaceutical Polymorphs by Isothermal Calorimetry

Physicochemical Characterization of Tamoxifen Citrate Pseudopolymorphs, Methanolate and Ethanolate

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