Journal articles: 'Amorphous and Crystalline Forms of Drug'

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Kissi, Eric Ofosu, Keyoomars Khorami, and Thomas Rades. "Determination of Stable Co-Amorphous Drug–Drug Ratios from the Eutectic Behavior of Crystalline Physical Mixtures." Pharmaceutics 11, no. 12 (November 24, 2019): 628. http://dx.doi.org/10.3390/pharmaceutics11120628.

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Co-amorphous drug–drug systems have been developed with the overall aim of improving the physical stability of two or more amorphous drugs. Co-amorphous systems often show good physical stability, and higher solubility and dissolution rates compared to their crystalline counterparts. The aim of this study is to determine if eutectic mixtures of two drugs can form stable co-amorphous systems. Three drug–drug mixtures, indomethacin–naproxen (IND−NAP), nifedipine–paracetamol (NIF−PAR), and paracetamol–celecoxib (PAR−CCX), were investigated for their eutectic and co-amorphization behavior as well as their physical stability in the co-amorphous form. The phase diagrams of the crystalline mixtures and the thermal behavior of the co-amorphous systems were analyzed by differential scanning calorimetry. The solid-state form and physical stability of the co-amorphous systems were analyzed using X-ray powder diffractometry during storage at room temperature at dry conditions. Initial eutectic screening using nifedipine (NIF), paracetamol (PAR), and celecoxib (CCX) indicated that IND−NAP, NIF−PAR, and PAR−CCX can form eutectic mixtures. Phase diagrams were then constructed using theoretical and experimental values. These systems, at different drug-to-drug ratios, were melted and cooled to form binary mixtures. Most mixtures were found to be co-amorphous systems, as they were amorphous and exhibited a single glass transition temperature. The stability study of the co-amorphous systems indicated differences in their physical stability. Comparing the phase diagrams with the physical stability of the co-amorphous mixtures, it was evident that the respective drug–drug ratio that forms the eutectic point also forms the most stable co-amorphous system. The eutectic behavior of drug–drug systems can thus be used to predict drug ratios that form the most stable co-amorphous systems.

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Webster, Gregory K., Cynthia A. Pommerening, Whitney W. Harman, Mathew A. Gragg, Jian-Hwa Han, and Daniel J. Taylor. "Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations." Current Pharmaceutical Analysis 16, no. 5 (June 15, 2020): 529–38. http://dx.doi.org/10.2174/1573412915666181210144338.

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Background: Enabling formulations have been implemented by the pharmaceutical industry as an effective tool for keeping Active Pharmaceutical Ingredient (API) in an amorphous state. Upon dosing in the amorphous state, many drugs which fail to demonstrate bioactivity due to the limited solubility and bioavailability of their crystalline form become bioavailable. Purpose: The analytical techniques use today for crystallinity detection are challenged by the sensitivity and robustness needed to achieve a 5% quantitation limit in low dose drug products. Our laboratory has developed a novel procedure capable of meeting this sensitivity and selectivity requirement. This is achieved by exploiting the differences in kinetic solubility of the formulated amorphous and free crystalline forms of API currently being used in dosage form platforms. Methods: Representative amorphous drug formulations were prepared and spiked with varying levels of crystalline drug substances to evaluate the selectivity and recovery of the crystalline drug substance from the product formulation. Kinetic solubility testing using a (i) Particle wetting phase, (ii) Particle suspending/erosion phase, (iii) Sampling time point and (iv) A total recovery determination for the drug substance. Results: The method selectively and quantitatively distinguishes crystalline drug substance from amorphous drug substance for samples spiked from 2.5% to 10% of the nominal label concentration of the API in the dosage form matrix. Conclusion: The kinetic solubility approach reported here achieves sensitive crystallinity quantitation for low drug level amorphous drug formulations at levels not yet achieved by complimentary analytical techniques.

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Cheung, Eugene, Maxwell Terban, Simon Billinge, Paul Krolikowski, and Steve Hollis. "Recrystallization behavior of amorphous and crystalline lactose from TSPDF." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C864. http://dx.doi.org/10.1107/s2053273314091359.

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Lactose is a disaccharide sugar of galactose and glucose that is most commonly associated with milk. Its importance to the food and animal product industry cannot be overstated, as it is involved in aspects as diverse as baking, confectionary, and infant products. The other major use of lactose is in the pharmaceutical industry. The mildly sweet and loosely bland flavor of lactose has lent to its use as a stabilizer and excipient in pharmaceutical products. Despite the wide range of applications for this material, there is still much to be studied. While it is known to exist in several crystalline forms and as two anomers, α and β, characterized by the flipping of a hydroxide group on the glucose ring, the amorphous form of lactose is less understood. Yet it is this amorphous form which may play a crucial role in the physicochemical stability of amorphous drug dispersions. In order to fully understand the structural changes which lactose undergoes when converted from a crystalline to amorphous material, total scattering experiments coupled with PDF analysis for structural identification of amorphous lactose of different origins were undertaken with the goal of understanding the recrystallization behavior of this versatile material. Samples measured included commercial forms of lactose, crystalline and amorphous, and amorphous forms obtained by melt quenching and lyophilization. Recrystallization was followed for the amorphous forms by measuring characteristic samples aged at 400C/75% RH, which is a standard condition for stressing pharmaceutical materials to extrapolate shelf-life. By fitting the PDF curves to a structural model of lactose, and refining with the characteristic function for a sphere of radius r, an estimate of the coherence length of atom-atom correlations for a give sample provides a measure of the growth progression, from single molecule to crystallite for the lactose samples. Coupled with data from NMR spectroscopy, TSPDF analysis is teasing out the nuances of the recrystallization behavior of lactose.

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Matzger, Adam J., Kuthuru Suresh, Vilmalí López-Mejías, Saikat Roy, and Daniel F. Camacho. "Leveraging Framework Instability: A Journey from Energy Storage to Drug Delivery." Synlett 31, no. 16 (June 18, 2020): 1573–80. http://dx.doi.org/10.1055/s-0040-1707139.

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Amorphous pharmaceuticals often suffer from poor physical stability, which can negate their high solubility, fast dissolution rate, and better oral bioavailability vs. crystalline forms. This represents a major hurdle to processing, storage, and delivery of amorphous pharmaceuticals. Several approaches to addressing these problems have been pursued, but there is still a need for a general method for stabilizing the amorphous form. We describe a novel approach using a water-unstable metal-organic framework as a drug delivery vehicle that demonstrates improved amorphous form stability accompanied by remarkably enhanced solubility and a fast dissolution rate. This research project spanned eleven years from conception to realization and dissemination. With origins in understanding the stability or porous solids for energy storage materials, the work also highlights potential of basic science understanding to illuminate new areas of application.

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Hancock, Bruno C., Glenn T. Carlson, Dauda D. Ladipo, Beth A. Langdon, and Matthew P. Mullarney. "Comparison of the mechanical properties of the crystalline and amorphous forms of a drug substance." International Journal of Pharmaceutics 241, no. 1 (July 2002): 73–85. http://dx.doi.org/10.1016/s0378-5173(02)00133-3.

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Puri, Vibha, Ajay K. Dantuluri, Mahesh Kumar, N. Karar, and Arvind K. Bansal. "Wettability and surface chemistry of crystalline and amorphous forms of a poorly water soluble drug." European Journal of Pharmaceutical Sciences 40, no. 2 (May 2010): 84–93. http://dx.doi.org/10.1016/j.ejps.2010.03.003.

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Sip, Szymon, Natalia Rosiak, Andrzej Miklaszewski, Patrycja Talarska, Ewa Dudziec, and Judyta Cielecka-Piontek. "Amorphous Form of Carvedilol Phosphate—The Case of Divergent Properties." Molecules 26, no. 17 (September 1, 2021): 5318. http://dx.doi.org/10.3390/molecules26175318.

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The amorphous form of carvedilol phosphate (CVD) was obtained as a result of grinding. The identity of the obtained amorphous form was confirmed by powder X-ray diffraction (PXRD), different scanning calorimetry (DSC), and FT-IR spectroscopy. The process was optimized in order to obtain the appropriate efficiency and time. The crystalline form of CVD was used as the reference standard. Solid dispersions of crystalline and amorphous CVD forms with hydrophilic polymers (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®) were obtained. Their solubility at pH 1.2 and 6.8 was carried out, as well as their permeation through a model system of biological membranes suitable for the gastrointestinal tract (PAMPA-GIT) was established. The influence of selected polymers on CVD properties was defined for the amorphous form regarding the crystalline form of CVD. As a result of grinding (four milling cycles lasting 15 min with 5 min breaks), amorphous CVD was obtained. Its presence was confirmed by the “halo effect” on the diffraction patterns, the disappearance of the peak at 160.5 °C in the thermograms, and the changes in position/disappearance of many characteristic bands on the FT-IR spectra. As a result of changes in the CVD structure, its lower solubility at pH 1.2 and pH 6.8 was noted. While the amorphous dispersions of CVD, especially with Pluronic® F-127, achieved better solubility than combinations of crystalline forms with excipients. Using the PAMPA-GIT model, amorphous CVD was assessed as high permeable (Papp > 1 × 10−6 cm/s), similarly with its amorphous dispersions with excipients (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®), although in their cases, the values of apparent constants permeability were decreased.

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Mudie, Deanna M., Aaron M. Stewart, Jesus A. Rosales, Nishant Biswas, Molly S. Adam, Adam Smith, Christopher D. Craig, Michael M. Morgen, and David T. Vodak. "Amorphous Solid Dispersion Tablets Overcome Acalabrutinib pH Effect in Dogs." Pharmaceutics 13, no. 4 (April 15, 2021): 557. http://dx.doi.org/10.3390/pharmaceutics13040557.

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Calquence® (crystalline acalabrutinib), a commercially marketed tyrosine kinase inhibitor (TKI), exhibits significantly reduced oral exposure when taken with acid-reducing agents (ARAs) due to the low solubility of the weakly basic drug at elevated gastric pH. These drug–drug interactions (DDIs) negatively impact patient treatment and quality of life due to the strict dosing regimens required. In this study, reduced plasma drug exposure at high gastric pH was overcome using a spray-dried amorphous solid dispersion (ASD) comprising 50% acalabrutinib and 50% hydroxypropyl methylcellulose acetate succinate (HPMCAS, H grade) formulated as an immediate-release (IR) tablet. ASD tablets achieved similar area under the plasma drug concentration–time curve (AUC) at low and high gastric pH and outperformed Calquence capsules 2.4-fold at high gastric pH in beagle dogs. In vitro multicompartment dissolution testing conducted a priori to the in vivo study successfully predicted the improved formulation performance. In addition, ASD tablets were 60% smaller than Calquence capsules and demonstrated good laboratory-scale manufacturability, physical stability, and chemical stability. ASD dosage forms are attractive for improving patient compliance and the efficacy of acalabrutinib and other weakly basic drugs that have pH-dependent absorption.

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Manogna, Katta, P. Nagaveni, and K. Thyagaraju. "Enhancement of solubility of poorly soluble drugs by solid dispersion: An Overview." Indian Journal of Pharmaceutical and Biological Research 5, no. 04 (December 31, 2017): 17–23. http://dx.doi.org/10.30750/ijpbr.5.4.4.

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Most of the newly invented chemical drug moieties are poorly water soluble. According to BCS classification, class II and IV drugs are considered as poorly water soluble. So enhancement of oral absorption and bioavailability of solid dosage forms remains a challenge to formulation scientists due to their solubility criteria. Therefore many techniques are being explored to enhance the solubility of poor soluble drugs. Solid dispersion is one of the most important method for enhance the solubility (dissolution rate) and hence oral bioavailability of poorly soluble drugs. In solid dispersion the particle size of drug is reduced or a crystalline pure drug is converted into amorphous form and hence the solubility is increased. Polymer incorporating in solid dispersion technology is usually hydrophilic in nature and also showing compatibility with the drug to enhance the drug solubility. This review mainly discus about solid dispersion, preparation methods, and finally characterization.

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Talaczyńska, Alicja, Kornelia Lewandowska, Anna Jelińska, Piotr Garbacki, Agnieszka Podborska, Przemysław Zalewski, Irena Oszczapowicz, Adam Sikora, Maciej Kozak, and Judyta Cielecka-Piontek. "Application of Vibrational Spectroscopy Supported by Theoretical Calculations in Identification of Amorphous and Crystalline Forms of Cefuroxime Axetil." Scientific World Journal 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/921049.

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FT-IR and Raman scattering spectra of cefuroxime axetil were proposed for identification studies of its crystalline and amorphous forms. An analysis of experimental spectra was supported by quantum-chemical calculations performed with the use of B3LYP functional and 6-31G(d,p) as a basis set. The geometric structure of a cefuroxime axetil molecule, HOMO and LUMO orbitals, and molecular electrostatic potential were also determined by using DFT (density functional theory). The benefits of applying FT-IR and Raman scattering spectroscopy for characterization of drug subjected to degradation were discussed.

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Mehata, Abhishesh K., Deepa Dehari, Senthil R. Ayyannan, and Madaswamy S. Muthu. "X-ray Powder Diffraction Spectroscopy as a Robust Tool in Early Predicting Bioavailability of Pharmaceutical Formulation Containing Polymorphic Drug Substance." Drug Delivery Letters 10, no. 3 (September 10, 2020): 250–54. http://dx.doi.org/10.2174/2210303110999200519074306.

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: X-ray powder diffraction (XRPD) is a unique, solid-state analytical tool used to study the 3D structure of small or macromolecules by their x-ray diffraction or scattering patterns. X-ray diffraction by a crystal reflects the periodicity of crystal architecture; any imperfections within the crystal architecture can be easily identified by its poor diffraction pattern. Recently, an open crystallography database reported that more than 85 % of drug compounds are crystalline and exist in different polymorphic states. Physicochemical properties of pharmaceutical drug products composed of active pharmaceutical ingredients (APIs) and excipients are interdependent on the physical state and forms in which APIs are distributed in excipients that determine the in-vivo and ex-vivo performance of the product. Amorphous APIs have relatively higher dissolution and bioavailability than crystalline form but with lower phase stability. During the formulation development and storage phase, the conversion is higher that largely impacts the bioavailability of the drug product. In this manuscript, we have presented the case study of itraconazole and apigenin; both are crystalline APIs, that, with the help of solid dispersion technology, are converted into amorphous drug products with enhanced oral bioavailability. The realtime monitoring of the physical form of API in the formulation was possible with the help of XRPD and other supporting data obtained from differential scanning calorimeter (DSC), which can be correlated with the dissolution and in-vivo performance of the formulation.

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Suzuki, Hironori, Moemi Iwata, Masataka Ito, and Shuji Noguchi. "X-ray Absorption Near-Edge Spectroscopy Analysis of Indomethacin in Crystalline Forms and in Amorphous Solid Dispersions." Molecular Pharmaceutics 18, no. 9 (August 10, 2021): 3475–83. http://dx.doi.org/10.1021/acs.molpharmaceut.1c00405.

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Shayanfar, Ali, Hamed Ghavimi, Hamed Hamishekar, and Abolghasem Jouyban. "Coamorphous Atorvastatin Calcium to Improve its Physicochemical and Pharmacokinetic Properties." Journal of Pharmacy & Pharmaceutical Sciences 16, no. 4 (October 1, 2013): 577. http://dx.doi.org/10.18433/j3xs4s.

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Purpose: Atorvastatin calcium (ATC) is classified as class II (low solubility and high permeability) compound according to the biopharmaceutical classification system. The amorphous form of ATC possesses higher solubility, dissolution rate, and bioavailability than its crystalline form. Coamorphous drug system is a new and emerging method to prepare stable amorphous forms, in this case leading to the improved stability of ATC in dissolution medium. Methods: In this study, coamorphous form of ATC and nicotinamide (ATC-NIC) was prepared from solvent evaporation method and characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and powder X-ray diffraction (PXRD). The intrinsic dissolution rate and solubility of ATC-NIC were determined along with plasma concentrations of ATC using HPLC after oral dosing in rats. Results: The crystalline ATC was converted to coamorphous form revealing a molecular interaction between ATC and NIC. The intrinsic dissolution rate, solubility and plasma concentration of coamorphous ATC-NIC are higher than those of crystalline ATC. ATC-NIC coamorphous system showed greater solution stability than those reported in the literature for amorphous ATC. Conclusions: Coamorphous ATC-NIC has improved physicochemical and pharmacokinetic properties as compared to ATC. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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Lovskaya, Daria, and Natalia Menshutina. "Alginate-Based Aerogel Particles as Drug Delivery Systems: Investigation of the Supercritical Adsorption and In Vitro Evaluations." Materials 13, no. 2 (January 10, 2020): 329. http://dx.doi.org/10.3390/ma13020329.

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The present work focuses on the preparation of alginate-based aerogels in the form of particles for their further study as potential drug delivery systems (solid dosage forms). The dripping method was used to prepare certain gel particles, and supercritical drying was used to obtain final alginate-based aerogel particles. Three model active substances (ketoprofen, nimesulide, loratadine) were impregnated into the obtained aerogels using the supercritical adsorption process. Using the method of X-ray analysis, it was shown that the in the obtained drug-loaded aerogels the corresponding active substances are in an amorphous state, and the stability of this state after six months of storage is confirmed. In vitro dissolution tests for obtained drug-loaded aerogels was performed. For each sample, an appropriate dissolution medium (with certain pH) was determined. In vitro investigations showed the increasing of the release rate for all model active substances. Time was required to release and dissolve 50% of the active drug from drug-loaded aerogels (T1/2), reduced in comparison with pure active drugs in crystalline form. Obtained results provide insight into the application of alginate-based aerogel particles as a drug delivery system to improve pharmacokinetic properties of certain active drugs.

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Ma, Xiangyu, Felix Müller, Siyuan Huang, Michael Lowinger, Xu Liu, Rebecca Schooler, and Robert O. Williams. "Influence of Carbamazepine Dihydrate on the Preparation of Amorphous Solid Dispersions by Hot Melt Extrusion." Pharmaceutics 12, no. 4 (April 20, 2020): 379. http://dx.doi.org/10.3390/pharmaceutics12040379.

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Amorphous solid dispersions (ASDs) are commonly used in the pharmaceutical industry to improve the dissolution and bioavailability of poorly water-soluble drugs. Hot melt extrusion (HME) has been employed to prepare ASD based products. However, due to the narrow processing window of HME, ASDs are normally obtained with high processing temperatures and mechanical stress. Interestingly, one-third of pharmaceutical compounds reportedly exist in hydrate forms. In this study, we selected carbamazepine (CBZ) dihydrate to investigate its solid-state changes during the dehydration process and the impact of the dehydration on the preparation of CBZ ASDs using a Leistritz micro-18 extruder. Various characterization techniques were used to study the dehydration kinetics of CBZ dihydrate under different conditions. We designed the extrusion runs and demonstrated that: 1) the dehydration of CBZ dihydrate resulted in a disordered state of the drug molecule; 2) the resulted higher energy state CBZ facilitated the drug solubilization and mixing with the polymer matrix during the HME process, which significantly decreased the required extrusion temperature from 140 to 60 °C for CBZ ASDs manufacturing compared to directly processing anhydrous crystalline CBZ. This work illustrated that the proper utilization of drug hydrates can significantly improve the processability of HME for preparing ASDs.

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Ouazib, Farid, Naima Bouslah Mokhnachi, Nabila Haddadine, and Regis Barille. "Role of polymer/polymer and polymer/drug specific interactions in drug delivery systems." Journal of Polymer Engineering 39, no. 6 (July 26, 2019): 534–44. http://dx.doi.org/10.1515/polyeng-2018-0403.

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Abstract Drug delivery systems based upon the blending of Arabic gum and poly(N-vinylpyrrolidone) (AG/PVP) were prepared for the controlled release of acebutolol (Acb) hydrochloride. The prepared blends containing Acb were characterized using different techniques. The presence of physical interactions between the drug and polymer matrices was observed with Fourier-transform infrared spectroscopy. These interactions resulted in the transition of the drug from a crystalline to an amorphous state into the polymeric matrices, as demonstrated by differential scanning calorimetry and X-ray diffraction analysis. The thermogravimetric analysis study confirmed the presence of these interactions, which had a stabilizing effect on the drug against both thermal degradation and crystallinity. The in vitro release of Acb from the AG/PVP polymer system was investigated. Each drug-loaded system was used in a tablet formulation. Moreover, an in vitro dissolution study was carried out in three different dissolution media, and comparison of the dissolution profiles of the different dosage forms revealed that the polymer blend matrix had a better release-retarding efficiency. To better understand the release mechanism, the dissolution data were fitted to various release kinetic models.

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Vogt, Frederick G., Hao Yin, Rachel G. Forcino, and Lianming Wu. "17O Solid-State NMR as a Sensitive Probe of Hydrogen Bonding in Crystalline and Amorphous Solid Forms of Diflunisal." Molecular Pharmaceutics 10, no. 9 (July 29, 2013): 3433–46. http://dx.doi.org/10.1021/mp400275w.

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Nowak, Maciej, Maciej Gajda, Przemysław Baranowski, Patrycja Szymczyk, Bożena Karolewicz, and Karol P. Nartowski. "Stabilisation and Growth of Metastable Form II of Fluconazole in Amorphous Solid Dispersions." Pharmaceutics 12, no. 1 (December 20, 2019): 12. http://dx.doi.org/10.3390/pharmaceutics12010012.

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The crystallisation of metastable drug polymorphs in polymer matrices has been reported as a successful approach to enhance the solubility of poorly water-soluble drug molecules. This can be achieved using different polymers, drug to polymer ratios and formulation techniques enabling the formation of stable nuclei and subsequent growth of new or metastable drug polymorphs. In this work we elucidated the polymorphism behaviour of a model compound fluconazole (FLU) embedded in solid dispersions with amorphous Soluplus® (SOL) obtained using spray drying and fusion methods. The effect of humidity on the stability of FLU in the obtained dispersions was also evaluated. FLU at a drug content below 40 wt. % stayed amorphous in the dispersions prepared using the fusion method and crystallised exclusively into metastable form II at a drug content above 40 wt. % and 70% relative humidity (RH) conditions. In contrast, a mixture of forms I, II and hydrate of FLU was detected in the spray dried formulations after 14 days of storage at 40 °C/40% RH, with preferential growth of thermodynamically stable form I of FLU. This study highlights the importance of preparation techniques and the drug:polymer ratio in the formulation of amorphous solid dispersions and provides further understanding of the complex crystallisation behaviour of amorphous pharmaceuticals encapsulated in the polymer matrixes.

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Kogawa, Ana Carolina, Selma Gutierrez Antonio, and Hérida Regina Nunes Salgado. "Characterization of Polymorphic Forms of Rifaximin." Journal of AOAC INTERNATIONAL 99, no. 4 (July 1, 2016): 964–71. http://dx.doi.org/10.5740/jaoacint.16-0053.

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Abstract Rifaximin is a gut-selective oral antimicrobial that has no systemic adverse effects compared with placebo. It is used for the treatment of hepatic encephalopathy, traveler's diarrhea, irritable bowel syndrome, Clostridium difficile infection, ulcerative colitis, and acute diarrhea. The crystalline form present in rifaximin, α, has minimal systemic absorption compared to the amorphous form. The objective of this study was to obtain polymorphic forms of rifaximin using recrystallization processes. The forms were characterized and studied by thermal analysis, X-ray powder diffraction, scanning electron microscopy, and solubility testing. Six polymorphic forms of rifaximin, designated I–VI, were obtained by the crystallization process by evaporation of the solvent. Some polymorphic forms obtained in this work may not have the same excellent tolerability as the reference medicine; therefore, studies such as these are extremely important and point to the need for greater requirements by the regulatory agencies overseeing polymorph analysis of the raw materials used in the manufacture of medicines marketed globally. These analyses are not required in the majority of official compendia. Partnerships among industries, research centers, and universities would be a viable way to consolidate research in this area and contribute to improving the quality of solid drugs.

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Mosqueira, V. C. F., E. A. Leite, C. M. Barros, J. M. C. Vilela, and M. S. Andrade. "Polymeric Nanostructures for Drug Delivery: Characterization by Atomic Force Microscopy." Microscopy and Microanalysis 11, S03 (December 2005): 36–39. http://dx.doi.org/10.1017/s143192760505083x.

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Formal definitions of nanotechnological devices for drug delivery typically feature the requirements that the device itself or its essential components be man-made, and in the 1-1000 nm range in at least one dimension [1]. The known nanovectors or nanostructures can be filled with drugs for different therapies and for diagnostical aims. Targeting moieties can also be attached to their surface. Polymeric nanovectors are generally made from biodegradable polymers such as polyesters, for example, poly-e-caprolactone (PCL). The drug delivery system known as nanocapsules (NCs) can be defined as a complex nanovector that is composed by a polymeric wall surrounding an oil core, where lipophilic drugs can be encapsulated. The advantages of NCs compared to other nanovectors are the high entrapment efficiencies of lipophilic drugs, low polymer content and low inherent toxicity. On the other hand, because of its complex blend of components NCs suspension allow several forms of nanovectors to be present at the same time, such as nanospheres, liposomes and nanoemulsions [2]. These ‘contaminants’ would be present in accordance with the type of formulation and method of preparation. Atomic force microscopy (AFM) has been used as a method for imaging the surfaces of liposomes [3] and nanospheres [4] allowing information in nanoscaled dimensions. In the present work, the NCs were prepared loading two different drugs, the antifungal albaconazole (ABZ), showing a crystalline drug structure and the antimalarial halofantrine (Hf) free base, having an amorphous form. These drugs possess high lipophilic character, which favours the association of the drug with the oily core, with drug loadings above 94%. Herein we studied the behavior of ABZ-loaded and Hf-loaded NCs through the AFM technique, searching to analyze and understand possible alterations induced by the drug inclusion in these nanostructures.

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Tan, Deck Khong, Mohammed Maniruzzaman, and Ali Nokhodchi. "Development and Optimisation of Novel Polymeric Compositions for Sustained Release Theophylline Caplets (PrintCap) via FDM 3D Printing." Polymers 12, no. 1 (December 21, 2019): 27. http://dx.doi.org/10.3390/polym12010027.

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This study reports a thorough investigation combining hot-melt extrusion technology (HME) and a low-cost fused deposition modelling (FDM) 3D printer as a continuous fabrication process for a sustained release drug delivery system. The successful implementation of such an approach presented herein allows local hospitals to manufacture their own medical and pharmaceutical products on-site according to their patients’ needs. This will help save time from waiting for suitable products to be manufactured off-site or using traditional manufacturing processes. The filaments were produced by optimising various compositions of pharmaceutical-grade polymers, such as hydroxypropyl cellulose (HPC), Eudragit® (RL PO), and polyethylene glycol (PEG), whereas theophylline was used as a model thermally stable drug. For the purpose of the study, twin-screw hot-melt extrusion (HME) was implemented from the view that it would result in the formation of solid dispersion of drug in the polymeric carrier matrices by means of high shear mixing inside the heated barrel. Four filament compositions consisting of different ratios of polymers were produced and their properties were assessed. The mechanical characterisation of the filaments revealed quite robust properties of the filaments suitable for FDM 3D printing of caplets (PrintCap), whereas the solid-state analyses conducted via DSC and XRD showed amorphous nature of the crystalline drug dispersed in the polymeric matrices. Moreover, the surface analysis conducted via SEM showed a smooth surface of the produced filaments as well as caplets where no drug crystals were visible. The in vitro drug release study showed a sustained release profile over 10 h where about 80% of the drug was released from the printed dosage forms. This indicates that our optimised 3D printed caplets could be suitable for the development of sustained release on-demand drug delivery systems.

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Sussich, Fabiana, Ranieri Urbani, Francesco Princivalle, and Attilio Cesàro. "Polymorphic Amorphous and Crystalline Forms of Trehalose." Journal of the American Chemical Society 120, no. 31 (August 1998): 7893–99. http://dx.doi.org/10.1021/ja9800479.

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Bruni, G., C. Milanese, V. Berbenni, F. Sartor, M. Villa, and A. Marini. "Crystalline and amorphous phases of a new drug." Journal of Thermal Analysis and Calorimetry 102, no. 1 (November 29, 2009): 297–303. http://dx.doi.org/10.1007/s10973-009-0614-2.

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Orellana-Tavra, Claudia, Emma F. Baxter, Tian Tian, Thomas D. Bennett, Nigel K. H. Slater, Anthony K. Cheetham, and David Fairen-Jimenez. "Amorphous metal–organic frameworks for drug delivery." Chemical Communications 51, no. 73 (2015): 13878–81. http://dx.doi.org/10.1039/c5cc05237h.

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Saleki‐Gerhardt, Azita, Joseph G. Stoweell, Stephen R. Byrn, and George Zografi. "Hydration and Dehydration of Crystalline and Amorphous Forms of Raffinose." Journal of Pharmaceutical Sciences 84, no. 3 (March 1995): 318–23. http://dx.doi.org/10.1002/jps.2600840311.

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Bhattacharjee, S., M. K. Paria, and H. S. Maiti. "Preparation of amorphous and crystalline forms of barium titanyl oxalate." Ceramics International 16, no. 4 (January 1990): 211–14. http://dx.doi.org/10.1016/0272-8842(90)90068-q.

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Pyo, Sang-Hyun, Jin-Suk Cho, Ho-Joon Choi, and Byung-Hee Han. "Preparation and Dissolution Profiles of the Amorphous, Dihydrated Crystalline, and Anhydrous Crystalline Forms of Paclitaxel." Drying Technology 25, no. 10 (October 2007): 1759–67. http://dx.doi.org/10.1080/07373930701593180.

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Guttman, Lester. "Ring structure of the crystalline and amorphous forms of silicon dioxide." Journal of Non-Crystalline Solids 116, no. 2-3 (February 1990): 145–47. http://dx.doi.org/10.1016/0022-3093(90)90686-g.

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Al-Obaidi, Hisham, Mridul Majumder, and Fiza Bari. "Amorphous and Crystalline Particulates: Challenges and Perspectives in Drug Delivery." Current Pharmaceutical Design 23, no. 3 (February 20, 2017): 350–61. http://dx.doi.org/10.2174/1381612822666161107162109.

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Crystalline and amorphous dispersions have been the focus of academic and industrial research due to their potential role in formulating poorly water-soluble drugs. This review looks at the progress made starting with crystalline carriers in the form of eutectics moving towards more complex crystalline mixtures. It also covers using glassy polymers to maintain the drug as amorphous exhibiting higher energy and entropy. However, the amorphous form tends to recrystallize on storage, which limits the benefits of this approach. Specific interactions between the drug and the polymer may retard this spontaneous conversion of the amorphous drug. Some studies have shown that it is possible to maintain the drug in the amorphous form for extended periods of time. For the drug and the polymer to form a stable mixture they have to be miscible on a molecular basis. Another form of solid dispersions is pharmaceutical co-crystals, for which research has focused on understanding the chemistry, crystal engineering and physico-chemical properties. USFDA has issued a guidance in April 2013 suggesting that the co-crystals as a pharmaceutical product may be a reality; but just not yet! While some of the research is still oriented towards application of these carriers, understanding the mechanism by which drug-carrier miscibility occurs is also covered. Within this context is the use of thermodynamic models such as Flory-Huggins model with some examples of studies used to predict miscibility.

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Newman, Ann. "XRPD to Characterize Disordered and Amorphous Pharmaceutical Samples." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1558. http://dx.doi.org/10.1107/s2053273314084411.

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X-ray powder diffraction is commonly used to characterize pharmaceutical samples to identify crystalline forms as well as differentiate crystalline vs amorphous materials. Using XRPD for amorphous materials is usually limited to determining if the materials are fully amorphous or a mixture of crystalline and amorphous materials. Changes in the amorphous halos under various conditions (grinding, drying, water sorption, etc) are usually not investigated, but can give information on the system. This presentation will discuss other uses of XRPD in characterizing amorphous and disordered systems, including amorphous solid dispersions. Patterns involving nanocrystalline, amorphous, and defected samples will be presented and examples on using various methods to obtain further information from the data (pair distribution functions, pure curve resolution methods, diffuse scattering, and Rietveld analysis) will be included.

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Catti, Federica, Santos Hernández Gallego, Mónica Benito, Elies Molins, and Francisco Marquillas Olóndriz. "Characterization of crystalline forms of gaxilose, a diagnostic drug." Carbohydrate Research 499 (January 2021): 108232. http://dx.doi.org/10.1016/j.carres.2021.108232.

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Vranić, Edina. "Amorphous Pharmaceutical Solids." Bosnian Journal of Basic Medical Sciences 4, no. 3 (August 20, 2004): 35–39. http://dx.doi.org/10.17305/bjbms.2004.3383.

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Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. Their structure can be thought of as being similar to that of a frozen liquid with the thermal fluctuations present in a liquid frozen out, leaving only “static” structural disorder. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition.Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufactoring operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required.

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Phule, Pradeep P., Pierre A. Deymier, and Subhash H. Risbud. "Molecular dynamics simulations of some amorphous and crystalline photonic materials." Journal of Materials Research 5, no. 5 (May 1990): 1104–9. http://dx.doi.org/10.1557/jmr.1990.1104.

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Constant pressure molecular dynamics (MD) simulations have been used to simulate amorphous and crystalline forms of BaTiO3 and TiO2. Simulation results for pure RaTiO3 and TiO2 glasses show fourfold titanium coordination with a Ti–O bond distance of 1.8 Å, consistent with experimental evidence for the structure of titania doped glasses for all optical switching and ultra low expansivity (ULE) TiO2–SiO2 glasses. Radial distribution function data for crystalline, liquid, and amorphous forms of BaTiO3 were also obtained. The displacement polarization and its contribution to susceptibilities have been calculated by application of an electric field to the simulation cell. The calculated ionic dielectric constants (Ki) for simulated NaCI (crystal), TiO2 glass, and TiO2 (crystal) were 3.34, 5.96, and 19.4 as compared to the experimental values of ≍3.34, 3–10, and 78, respectively. The calculated cubic nonlinear susceptibility (ξ3) values for NaCI (crystal), TiO2 (glass), and TiO2 (crystal) were, respectively, 0.194, 2.175, and 4.68 (x 10−18m2V−2). The increase in ξ3 values is consistent with experimentally observed trends of the linear refractive indices. Improved agreement between experimental and calculated values of susceptibilities and dielectric constant was obtained for materials with higher ionicity.

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Labhasetwar, Vinod, S. V. Deshmukh, and A. K. Dorle. "Studies on Some Crystalline Forms of Ibuprofen." Drug Development and Industrial Pharmacy 19, no. 6 (January 1993): 631–41. http://dx.doi.org/10.3109/03639049309062971.

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Plater, M. John, and William T. A. Harrison. "Crystalline Forms of Trazodone Dihydrates." Molecules 26, no. 17 (September 3, 2021): 5361. http://dx.doi.org/10.3390/molecules26175361.

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In this study, treatment of anhydrous trazodone powder with ammonium carbamate in warm water crystallised two new polymorphs or dihydrates of trazodone after 5 h, whose structures were determined by X-ray single crystal diffraction. Each dihydrate contains infinite zigzag hydrogen-bonded chains of water molecules, which are stabilised by the N4 acceptor atom of the piperazine ring and the pendant carbonyl O1 atom of the triazole ring, as well as other water molecules. The strong dipole moment expected for the O1 atom makes it a good hydrogen bond acceptor for stabilising the chains of water molecules. Each molecule of trazodone has a similar conformation in both hydrates, except for the propyl chains, which adopt different conformations: anti-gauche in the β hydrate (triazole N-C-C-C and C-C-C-piperazine N) and anti-anti in the γ hydrate. Both piperazine rings adopt chair conformations, and the exocyclic N-C bonds are in equatorial orientations. The Hirshfeld surfaces and two-dimensional fingerprint plots for the polymorphs were calculated using CrystalExplorer17, which indicated contacts significantly shorter than the sum of the van der Waals radii in the vicinity of the piperazine N4 and triazole O1 atoms corresponding to the strong hydrogen bonds accepted by these atoms.

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Cheng, Yanhua, Shunjie Liu, Fengyan Song, Michidmaa Khorloo, Haoke Zhang, Ryan T. K. Kwok, Jacky W. Y. Lam, Zikai He, and Ben Zhong Tang. "Facile emission color tuning and circularly polarized light generation of single luminogen in engineering robust forms." Materials Horizons 6, no. 2 (2019): 405–11. http://dx.doi.org/10.1039/c8mh01092g.

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Gera, Tamás, Tomi Smausz, Judit Kopniczky, Gábor Galbács, Rita Ambrus, Piroska Szabó-Révész, and Béla Hopp. "Production of ibuprofen in crystalline and amorphous forms by Pulsed Laser Deposition (PLD)." Applied Surface Science 493 (November 2019): 359–67. http://dx.doi.org/10.1016/j.apsusc.2019.06.254.

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Bakare, M. S., K. T. Voisey, K. Chokethawai, and D. G. McCartney. "Corrosion behaviour of crystalline and amorphous forms of the glass forming alloy Fe43Cr16Mo16C15B10." Journal of Alloys and Compounds 527 (June 2012): 210–18. http://dx.doi.org/10.1016/j.jallcom.2012.02.127.

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Reeves, James B. "Efforts to Quantify Changes in Near-Infrared Spectra Caused by the Influence of Water, pH, Ionic Strength, and Differences in Physical State." Applied Spectroscopy 49, no. 2 (February 1995): 181–87. http://dx.doi.org/10.1366/0003702953963788.

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The application of near-infrared spectroscopy to high-moisture samples has shown that the accuracy does not match that found for dried materials. The objective of this work was to attempt to quantify the effects of water, pH, ionic strength, and differences in physical state on near-infrared spectra with the use of model compounds. Spectra were compared by regression analysis of second derivatives after spectral subtraction of water. Spectra from 4900 to 4100 cm−1 at a resolution of 4 cm−1 were examined. Regression results showed spectra to be more similar among amorphous sugars and among dissolved sugars than among crystalline sugars. Also, spectra of amorphous sugars were statistically more similar to spectra of dissolved sugars than to spectra of crystalline sugars. While the spectra of one dissolved or amorphous sugar were statistically similar, this was not true for amino acids. Spectra of amorphous amino acids were similar to those of crystalline forms and neither were similar to those of dissolved forms. Spectrally, polymeric carbohydrates appeared very similar to one another when dry and behaved like amino acids when wet. Finally, efforts to directly relate these findings to near-IR spectroscopy calibration problems will require further research.

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Dong, Junye, Rohan Ullal, Jie Han, Shanghai Wei, Xin Ouyang, Junzhe Dong, and Wei Gao. "Partially crystallized TiO2 for microwave absorption." Journal of Materials Chemistry A 3, no. 10 (2015): 5285–88. http://dx.doi.org/10.1039/c4ta05908e.

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Amorphous TiO₂ synthesized via Ti anodization is partially crystallized and displays strong microwave absorption ability. Interfacial electric field forms at the boundary of crystalline–amorphous phases due to the uneven oxygen-vacancy distributions in the two phases, amplifying the microwave absorption.

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Sedmale, Gaida M., and Vasily P. Kobyakov. "Amorphous Alumosilicophosphate Coatings for Niobium Alloys." Materials Science Forum 502 (December 2005): 237–42. http://dx.doi.org/10.4028/www.scientific.net/msf.502.237.

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In the proposed study the less known kinds of thermal barrier coatings used to protect niobium or its alloys against the oxygen corrosion at temperatures above 6000C are discussed. Coatings were obtained from glass in the system BaO(MgO)- Al2O3- SiO2-P2O5 with the softening temperature above 7000C. The development of amorphous coatings from glass includes the preparation of it, deposition on surface of niobium alloy Nb+1% Zr and high-temperature annealing process. The coating can be represented as a multilayer system – top glassy layer (20-25 µm), glasscrystalline (8-10µm) and crystalline interfacial layer (~ 5-8 µm). The interfacial layer forms in the result of diffusion of Nb in a narrow layer close to substrate. Interfacial layer is crystalline and is composed from fine NbP crystals. This layer is the determinative barrier for oxygen diffusion into the substrate at the maximum of operating temperature 950 0C.

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42

Modica de Mohac, Laura, Alison Keating, Maria de Fátima Pina, and Bahijja Raimi-Abraham. "Engineering of Nanofibrous Amorphous and Crystalline Solid Dispersions for Oral Drug Delivery." Pharmaceutics 11, no. 1 (December 24, 2018): 7. http://dx.doi.org/10.3390/pharmaceutics11010007.

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Poor aqueous solubility (<0.1 mg/mL) affects a significant number of drugs currently on the market or under development. Several formulation strategies including salt formation, particle size reduction, and solid dispersion approaches have been employed with varied success. In this review, we focus primarily on the emerging trends in the generation of amorphous and micro/nano-crystalline solid dispersions using electrospinning to improve the dissolution rate and in turn the bioavailability of poorly water-soluble drugs. Electrospinning is a simple but versatile process that utilizes electrostatic forces to generate polymeric fibers and has been used for over 100 years to generate synthetic fibers. We discuss the various electrospinning studies and spinneret types that have been used to generate amorphous and crystalline solid dispersions.

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Orellana-Tavra, Claudia, Milan Köppen, Aurelia Li, Norbert Stock, and David Fairen-Jimenez. "Biocompatible, Crystalline, and Amorphous Bismuth-Based Metal–Organic Frameworks for Drug Delivery." ACS Applied Materials & Interfaces 12, no. 5 (January 15, 2020): 5633–41. http://dx.doi.org/10.1021/acsami.9b21692.

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Angelini, P., P. S. Sklad, J. C. Sevely, and D. K. Hssein. "Evaluation of amorphous and crystalline SiC by extended energy loss fine structure (EXELFS) analysis." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 466–67. http://dx.doi.org/10.1017/s042482010010439x.

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Crystalline as well as amorphous forms of silicon carbide are materials which have important uses in many areas of materials science including structural ceramics, coatings, and semiconductors. The characterization of SiC by the use of the EXELFS technique yields radial distribution functions (RDF) which are sensitive to the structure and composition within near neighbor distances of either C or Si atoms. In this way a quantitative analysis of possible variations in “structure” can be made. EXELFS analyses of crystalline SiC are especially important in order to evaluate the method when comparison with results from the amorphous state are to be made. The EXELFS technique has previously been applied to study both crystalline as well as amorphous materials.Crystalline as well as amorphous SiC was evaluated. One specimen was a commercially available SiC single crystal. Two other specimens utilized a similar SiC starting material which had been made amorphous either by ion implantation with chromium or by irradiation from 300 kV electrons.

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Shityakov, Sergey, Norbert Roewer, Carola Y. Förster, Hai T. Tran, Wenjun Cai, and Jens-Albert Broscheit. "Investigation of Crystalline and Amorphous Forms of Aluminum and Its Alloys: Computational Modeling and Experiment." Nano 13, no. 03 (March 2018): 1850026. http://dx.doi.org/10.1142/s1793292018500261.

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The purpose of this study is to investigate polycrystalline lattices of aluminum (Al) under the stress–strain conditions in all-atom molecular dynamics simulations and Al alloys using X-ray diffraction. Isothermal uniaxial tension and compression of these polycrystalline lattices showed no dislocation nucleation peaks, which correspond only to the Al monocrystal form. The best tensile and compressive resistance characteristics were observed for a material with the highest grain number ([Formula: see text]) due to the significant reduction of the face-centered cubic lattice in the metal structure. This process is mainly driven by the gradual elevation of the system’s kinetic energy. In the experiment, the amorphous Al alloys with higher manganese composition (20.5%) were investigated, matching the simulated amorphous structures. Overall, the results suggest that the increase in number of grains in Al lattices diminishes the stress–strain impact due to a more disordered atomic-scale (amorphous) metal composition.

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Bergese, P., I. Colombo, D. Gervasoni, and Laura E. Depero. "Assessment of the X-ray diffraction–absorption method for quantitative analysis of largely amorphous pharmaceutical composites." Journal of Applied Crystallography 36, no. 1 (January 21, 2003): 74–79. http://dx.doi.org/10.1107/s002188980201926x.

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Determination of the residual weight fraction of a crystalline drug in a largely amorphous pharmaceutical composite is still a challenging question. None of the quantitative X-ray diffraction (QXRD) methods found in the literature is suitable for these inclusion systems. The composite's diffraction patterns present a structured amorphous halo (arising from the amorphous matrix and drug molecular clusters) in which the crystalline drug peaks rise up. Moreover, the matrix traps a non-negligible quantity of water (which cannot be directly detected by X-ray diffraction) and the crystal structure of the drug may be unknown. In this work, a development of the QXRD analysis based on the diffraction–absorption technique is presented. The method is standardless, avoids the interpretation of the amorphous halo and the knowledge of the crystal structures of the phases, and takes into account the absorbed water. Results are in excellent agreement with those obtained by differential scanning calorimetry (DSC). The general features of the technique open its application to other classes of largely amorphous composite materials, like glass systems generated in the stabilization/solidification of toxic waste.

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Wiergowska, Gabriela, Dominika Ludowicz, Kamil Wdowiak, Andrzej Miklaszewski, Kornelia Lewandowska, and Judyta Cielecka-Piontek. "Combinations of Freeze-Dried Amorphous Vardenafil Hydrochloride with Saccharides as a Way to Enhance Dissolution Rate and Permeability." Pharmaceuticals 14, no. 5 (May 11, 2021): 453. http://dx.doi.org/10.3390/ph14050453.

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To improve physicochemical properties of vardenafil hydrochloride (VAR), its amorphous form and combinations with excipients—hydroxypropyl methylcellulose (HPMC) and β-cyclodextrin (β-CD)—were prepared. The impact of the modification on physicochemical properties was estimated by comparing amorphous mixtures of VAR to their crystalline form. The amorphous form of VAR was obtained as a result of the freeze-drying process. Confirmation of the identity of the amorphous dispersion of VAR was obtained through the use of comprehensive analysis techniques—X-ray powder diffraction (PXRD) and differential scanning calorimetry (DSC), supported by FT-IR (Fourier-transform infrared spectroscopy) coupled with density functional theory (DFT) calculations. The amorphous mixtures of VAR increased its apparent solubility compared to the crystalline form. Moreover, a nearly 1.3-fold increase of amorphous VAR permeability through membranes simulating gastrointestinal epithelium as a consequence of the changes of apparent solubility (Papp crystalline VAR = 6.83 × 10−6 cm/s vs. Papp amorphous VAR = 8.75 × 10−6 cm/s) was observed, especially for its combinations with β-CD in the ratio of 1:5—more than 1.5-fold increase (Papp amorphous VAR = 8.75 × 10−6 cm/s vs. Papp amorphous VAR:β-CD 1:5 = 13.43 × 10−6 cm/s). The stability of the amorphous VAR was confirmed for 7 months. The HPMC and β-CD are effective modifiers of its apparent solubility and permeation through membranes simulating gastrointestinal epithelium, suggesting a possibility of a stronger pharmacological effect.

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Mesallati, Hanah, Anita Umerska, Krzysztof J. Paluch, and Lidia Tajber. "Amorphous Polymeric Drug Salts as Ionic Solid Dispersion Forms of Ciprofloxacin." Molecular Pharmaceutics 14, no. 7 (June 9, 2017): 2209–23. http://dx.doi.org/10.1021/acs.molpharmaceut.7b00039.

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Sriamornsak, Pornsak, S. Konthong, K. Burapapadh, and Srisagul Sungthongjeen. "Drug-Loaded Pectin Microparticles Prepared by Emulsion-Solvent Evaporation." Advanced Materials Research 506 (April 2012): 282–85. http://dx.doi.org/10.4028/www.scientific.net/amr.506.282.

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The aim of this study was to develop the pectin-based microparticles by emulsion-solvent evaporation technique. The effects of concentration and type of pectin and addition of glutaraldehyde on size, size distribution, drug crystalline state and drug dissolution from microparticles were investigated. The results showed that a model drug, indomethacin, could be encapsulated in microparticles. Higher molecular weight of pectin caused a larger in size of microparticles than the lower one. A high degree of esterification is preferred to stabilize the pectin microparticles. The powder x-ray diffractograms showed that all microparticles led to amorphous products while their physical mixture still showed the crystalline state of drug. Drug dissolution from the microparticles containing indomethacin and pectin was increased, resulting from the formation of an amorphous solid dispersion. Addition of glutaraldehyde, however, resulted in slower drug dissolution, compared to the formulations without glutaraldehyde or drug alone.

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Wei, Yuanfeng, Yunni Ling, Meiling Su, Lei Qin, Jianjun Zhang, Yuan Gao, and Shuai Qian. "Characterization and Stability of Amorphous Tadalafil and Four Crystalline Polymorphs." Chemical and Pharmaceutical Bulletin 66, no. 12 (December 1, 2018): 1114–21. http://dx.doi.org/10.1248/cpb.c18-00450.

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Journal articles on the topic 'Amorphous and Crystalline Forms of Drug'

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