Identification and quantification techniques of polymorphic forms - A review.

In the pharmaceutical industry, the unexpected appearance of crystalline forms could impact the therapeutic efficacy of an Active Pharmaceutical Ingredient (API). For quality control, a thorough qualitative and quantitative monitoring of pharmaceutical solid forms is essential to ensure the detection and the quantification of crystalline forms, wither different or with the same chemical composition (polymorphs) at a low detection level. The purpose of this paper was to review and highlight the importance of choosing adequate solid-state techniques for detection and quantification APIs that present polymorphism - based on limits of detection (LOD) and quantification (LOQ), pharmacopeias specifications, international guidelines and studies reported in the literature. To this study, the powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Infrared and Raman spectroscopies and solid-state nuclear magnetic resonance (NMR) were the solid-state techniques analyzed. Additionally, the Argentine, Brazilian, British, European, International, Japanese, Mexican and the United States of America pharmacopeias were reviewed. Based on the analysis performed, the advantages and disadvantages of these techniques, as well as the LOD and LOQ values of APIs were reported. In comparison to these solid-state techniques, reference material used for identification analyses should be previously identified with the corresponding polymorph. Without this previous procedure, the patterns, the spectra, and DSC curves of the reference material can only be used to confirm the mixture of solid forms, not being able to specify which polymorphs are contained in the sample. A major advantage of PXRD is the use of the calculated diffraction patterns obtained from the Crystallographic Information Frameworks (CIFs) files which could be used as a reference pattern without any other information, assistance technique, or physical standards. Regarding the quantification aspect, different pharmacopeias suggest various methods such as the PXRD combining with Rietveld method, which can be used to obtain lower LOD values for minority phases in the mixture of different substances without the need for a calibration curve. Raman spectroscopy can detect polymorphs in small particles and solid-state NMR spectroscopy is a powerful technique for quantification not only crystalline but also crystalline-amorphous mixtures. Finally, this review intends to be a useful tool to control, with efficiency and accuracy, the polymorphism of APIs in pharmaceutical compounds.

Mechanical Activation by Ball Milling as a Strategy to Prepare Highly Soluble Pharmaceutical Formulations in the Form of Co-Amorphous, Co-Crystals, or Polymorphs.

Almost half of orally administered active pharmaceutical ingredients (APIs) have low solubility, which affects their bioavailability. In the last two decades, several alternatives have been proposed to modify the crystalline structure of APIs to improve their solubility; these strategies consist of inducing supramolecular structural changes in the active pharmaceutical ingredients, such as the amorphization and preparation of co-crystals or polymorphs. Since many APIs are thermosensitive, non-thermal emerging alternative techniques, such as mechanical activation by milling, have become increasingly common as a preparation method for drug formulations. This review summarizes the recent research in preparing pharmaceutical formulations (co-amorphous, co-crystals, and polymorphs) through ball milling to enhance the physicochemical properties of active pharmaceutical ingredients. This report includes detailed experimental milling conditions (instrumentation, temperature, time, solvent, etc.), as well as solubility, bioavailability, structural, and thermal stability data. The results and description of characterization techniques to determine the structural modifications resulting from transforming a pure crystalline API into a co-crystal, polymorph, or co-amorphous system are presented. Additionally, the characterization methodologies and results of intermolecular interactions induced by mechanical activation are discussed to explain the properties of the pharmaceutical formulations obtained after the ball milling process.

Unveiling meloxicam monohydrate process of dehydration by an at-line vibrational multi-spectroscopy approach.

Meloxicam (MLX) is a non-steroidal anti-inflammatory drug, extensively used for inflammatory diseases and pain treatments, which exhibits five known solids forms. Form IV of MLX, a zwitterionic monohydrate (MH), is an emblematic hydrate case with promissory dissolution properties in a poorly soluble drug. However, the lack of information about MH stability regarding the dehydration process and phase transition impedes the development of further stability studies. A multi-spectroscopic/chemometric approach was implemented coupling middle- (MIR), near-infrared (NIR) and Raman spectroscopies to monitor the heat-mediated dehydration process of MH. The application of multivariate curve resolution-alternating least squares (MCR-ALS) to multi-source spectra by data fusion allow a complete view of the phenomena, improving the selectivity and precision to establish the transition temperatures and to identify involved species. It was revealed a two-step mechanism, where MH changes to Form V at 90 °C obtaining its complete dehydration at 130 °C, Form V remains unchanged during the temperature range 130-190 °C and then the polymorphic conversion to Form I starts, which reaches 100 % at 230 °C before melting MLX (248 °C). The findings of this work allow set targets in the process control of products using MH. Additionally, MCR-ALS detected an event not evidenced by conventional thermal analysis, the transformation of Form V to Form I.

Evaluation of chemometric approaches for polymorphs quantification in tablets using near-infrared hyperspectral images.

Near-Infrared hyperspectral imaging (HSI-NIR) is a useful technique for pharmaceutical research and industry alike. It can provide important surface information such as the polymorphs quantification and its distribution over the tablet. Several chemometric tools are applied for this purpose, with MCR-ALS and PLS regression being the most common approaches. In this work, a detailed comparison between these two approaches is performed. Beyond a "simple" regression comparison, a comparison of the score images (local quantification) was also evaluated. The system under study is tablets with ternary mixtures of Mebendazol (MBZ) polymorphs, microcrystalline cellulose and magnesium stearate. PLS models, in general, gave lower RMSEP (below 1.7% w/w for the three MBZ polymorphs) than the corresponding MCR-ALS predictions. Analyzing the distributions of the scores in the images of each sample shows clear differences between the PLS and MCR-ALS models. The MCR-ALS gave more chemical meaningful distribution maps for all polymorphs, even though the PLS accurately predicts the average concentration across the image. The problem is that the PLS models used the main spectral regions to quantify each MBZ polymorph, but at the same time undermines the minor spectroscopic changes caused by the different polymorphs. Although this may seem as a minor deviation from the truth, the results clearly show that this deviation is detrimental for the analysis of the spatial distribution of the analytes. These results indicate that the optimal multivariate model for multivariate images depend on the goal of the analysis: global quantification or a distribution analysis.

Two polymorphs of 2-(prop-2-yn-1-yl-oxy)naphthalene-1,4-dione: solvent-dependent crystallization.

The title compound, C13H8O3, crystallizes in two polymorphs, namely the monoclinic (space group P21/c) and triclinic (space group Pi) forms, obtained from N,N-di-methyl-formamide and isopropyl alcohol solutions, respectively. The mol-ecular structures and conformations in the two forms are essentially the same as each other. The naphtho-quinone ring systems are essentially planar with r.m.s. deviations of 0.015 and 0.029 Šfor the monoclinic and triclinic forms, respectively. The O-propargyl groups are coplanar with the naphtho-quinone units with r.m.s deviations ranging from 0.04 to 0.09 Å. In the monoclinic crystal, mol-ecules are linked via pairs of C-H⋯O hydrogen bonds, forming a tape structure running along [120]. The tapes are further linked by a C-H⋯π inter-action into a layer parallel to the ab plane. Adjacent layers are linked by another C-H⋯π inter-action. In the triclinic crystal, mol-ecules are linked via C-H⋯O and π-π inter-actions, forming a layer parallel to the ab plane. Adjacent layers are linked by a C-H⋯π inter-action.

Physics, chemistry, and Hirshfeld surface analyses of gamma-irradiated thalidomide to evaluate behavior under sterilization doses.

Thalidomide was indicated as a sedative and antiemetic and prescribed for pregnant women. Its tragic teratogenic effects culminated in withdrawal from the market. Since the discovery of its anti-angiogenic and anti-inflammatory actions, thalidomide has been used in the treatment of leprosy and multiple myeloma, which justify studies of its stability. We investigated the effects of irradiation of thalidomide up to 100 kGy (fourfold the usual sterilizing dose for pharmaceutics). The ß polymorph of thalidomide was obtained in an isothermal experiment at 270 °C. All samples underwent gamma irradiation for specific times. At different doses, decomposition of the pharmaceutical was not observed up to 100 kGy. The observed effect was angle turning between the phthalimide and glutarimide rings modulated by repulsion towards the carbonyl group, leading to a stable energetic configuration, as measured by the equilibrium in the torsion angle after irradiation. The thalidomide molecule has a center of symmetry, so a full turn starting from 57.3° will lead to an identical molecule. Further irradiation will start the process again. Samples irradiated at 30 and 100 kGy have more compact unit cells and a lower volume, which leads to an increase in the intermolecular hydrogen interaction within the unit cell, resulting in higher thermal stability for polymorph α.

Portable near-infrared instruments: Application for quality control of polymorphs in pharmaceutical raw materials and calibration transfer.

This work presents an evaluation of the analytical performance of three different portable near-infrared (NIR) instruments (denominated Port.1, Port.2 and Port.3) for quantifying mebendazole polymorphs (A, B and C) in pharmaceutical raw materials using multivariate calibration models. The performance of the portable instruments was compared with a benchtop one (FT-NIR Frontier spectrometer). In addition, calibration transfer between the benchtop and one of the portable instruments was also performed. For polymorph A, the Port.1 presented the lowest RMSEP value (1.01% w/w) even when compared to the FT-NIR instrument. For polymorphs B and C, the same Port.1 instrument presented RMSEP values of 2.09% w/w and 2.41% w/w, respectively, which were statistically similar to those obtained with the benchtop instrument. The LOD ranges (3.9-5.5 for polymorph A, 3.6-5.1 for polymorph B and 5.7-7.7 for polymorph C) obtained with the Port.1 was higher than those achieved with the benchtop NIR instrument, with high spectral resolution, signal-to-noise ratio and better wavelength reproducibility. Calibration transfer was performed between the benchtop NIR and Port.1 instruments. According to the results, the transferability of models is possible. The results obtained for complete recalibration of the portable instrument and those for the benchtop are comparable. The methods developed demonstrated a flexible, easy, cheap and fast way for quality control of MBZ polymorphs in incoming material, mainly in pharmaceutical laboratory chains.

Solubility and dissolution studies of tibolone polymorphs

ABSTRACT Different solid forms of an active pharmaceutical ingredient can have distinct chemical and physical characteristics. In this work, we studied the solubility and dissolution properties of the described tibolone polymorphic forms (I and II). Both forms were successively recrystallized and characterized by powder X-ray diffraction and attenuated total reflection infrared spectroscopy. Equilibrium solubility and dissolution profiles were performed for both forms. Solubility studies demonstrated that form II is statistically more soluble in water, 0.01 mol L-1 HCl and pH 4.5 acetate buffer. The solubility of forms I and II were explained in terms of crystal packing. Dissolution tests of tablets showed a lower release of polymorphic form II than form I from tablets. The results showed an impact of polymorphism on the quality of tibolone tablets and suggest that tibolone forms I and II can show distinct interactions with pharmaceutical excipients used in tablets. Therefore, only form I is acceptable for the preparation of tablet forms. Based on our results, we propose the quality control on tibolone raw materials using X-ray diffraction analysis and attenuated total reflection infrared spectroscopy.

A comparative study of the packing of two polymorphs of the nickel(II) pincer complex [2,6-bis(di-tert-butylphosphinoyl)-4-(3,5-dinitrobenzoyloxy)phenyl-κ(3)P,C(1),P']chloridonickel(II).

Pincer complexes can act as catalysts in organic transformations and have potential applications in materials, medicine and biology. They exhibit robust structures and high thermal stability attributed to the tridentate coordination of the pincer ligands and the strong σ metal-carbon bond. Nickel derivatives of these ligands have shown high catalytic activities in cross-coupling reactions and other industrially relevant transformations. This work reports the crystal structures of two polymorphs of the title Ni(II) POCOP pincer complex, [Ni(C29H41N2O8P2)Cl] or [NiCl{C6H2-4-[OCOC6H4-3,5-(NO2)2]-2,6-(OP(t)Bu2)2}]. Both pincer structures exhibit the Ni(II) atom in a distorted square-planar coordination geometry with the POCOP pincer ligand coordinated in a typical tridentate manner via the two P atoms and one arene C atom via a C-Ni σ bond, giving rise to two five-membered chelate rings. The coordination sphere of the Ni(II) centre is completed by a chloride ligand. The asymmetric units of both polymorphs consist of one molecule of the pincer complex. In the first polymorph, the arene rings are nearly coplanar, with a dihedral angle between the mean planes of 27.9 (1)°, while in the second polymorph, this angle is 82.64 (1)°, which shows that the arene rings are almost perpendicular to one another. The supramolecular structure is directed by the presence of weak C-H...O=X (X = C or N) interactions, forming two- and three-dimensional chain arrangements.

The use of the software JST-XRD for identification of crystalline phases in pharmaceutical raw materials and tablets / Uso do software JST-XRD para identifcação de fases cristalinas em insumos farmacêuticos e medicamentos

Study of polymorphism is of great importance for the pharmaceutical industry once polymorphs may display different physicochemical properties, which, in turn, may result in stability differences that can bring problems for the manufacturing stages and the quality of fnal products. Although research on organic polymorphs has greatly increased in the last decades, it still does not cover all needs for the pharmaceutical market. Techniques such as spectroscopy in the infrared region, nuclear magnetic resonance, thermal analysis, X-ray diffraction, etc., can be used to identify polymorphism. The polymorphism is a property of the crystalline solid state, and can be evaluated by X-ray diffraction once each polymorph exhibits one specifc X-ray diffraction pattern. The JST-XRD program is a tool designed to help the identifcation of crystalline phases (including polymorphs) present in pharmaceutical ingredients and tablets by using X-ray diffraction data obtained from scientifc articles and patents. This paper presents new implementations for the JST-XRD and describes its use in the analysis of active pharmaceutical ingredient and marketed tablets of norfloxacin, mebendazole and atorvastatin calcium. By the means of comparison, JSTXRD allowed identifying the crystalline phases in the diffraction patterns of the analyzed drugs, showing the program suitability for polymorphism research, pre-formulation and quality control in pharmaceutical industries. JST-XRD can also be used for educational purposes in undergraduate and graduate programs in order to show the potentiality of X-ray powder diffraction in polymorphism analysis.(AU)

O estudo do polimorfsmo é de grande importância na indústria farmacêutica porque os polimorfos podem apresentar diferentes propriedades físico-químicas, podendo resultar em diferenças na estabilidade e desse modo causar problemas nas etapas de manufatura e no produto fnal. Embora a pesquisa de moléculas orgânicas que apresentam polimorfsmo tenha aumentado bastante nas últimas décadas, ainda não contempla todas as necessidades do mercado farmacêutico. Para a identifcação de polimorfsmo podem ser utilizadas técnicas como espectroscopia na região do infravermelho, ressonância nuclear magnética, análise térmica (DSC), difração de raios X, etc. O polimorfsmo, por ser uma propriedade do estado sólido e cristalino, pode ser avaliado através da difração de raios X, já que cada polimorfo apresenta um padrão de difração de raios X único. O programa JST-XRD é uma ferramenta projetada para auxiliar a identifcação de fases cristalinas, incluindo polimorfos, presentes em insumos farmacêuticos e comprimidos, usando dados de difração de raios X obtidos em artigos científcos e patentes. Esse trabalho apresenta novas implementações no JST-XRD e descreve seu uso na análise de amostras de princípio ativo e comprimidos comerciais de norfloxacino, mebendazol e atorvastatina cálcica. Através das comparações realizadas, JSTXRD permitiu identifcar todas as fases cristalinas dos difratogramas dos fármacos analisados, mostrando que o programa é adequado para pesquisa em polimorfsmo; na pré-formulação e controle de qualidade em indústrias farmacêuticas, assim como para uso didático em cursos de graduação e pós-graduação a fm de mostrar as potencialidades da difração de raios X na análise de polimorfsmo.(AU)

NaOH treatment of chitosan films: Impact on macromolecular structure and film properties.

In this paper, we examine the significance of treatment with NaOH on chitosan (CH) film structure to obtain biodegradable materials for several applications. In order to determine the structure of the films, an analysis based on SEM, FTIR spectroscopy and X-ray diffraction data was performed. In addition, the consequences of this treatment were evaluated by swelling index measurements and mechanical testing. As result of FTIR and X-ray analysis, three effects were identified: the deprotonation and phosphate extraction, which allowed new hydrogen bonds to form, and a higher CH deacetylation. These studies also revealed that two hydrated and anhydrous polymorphs were present in the CH-NaOH films. Moreover, the new hydrogen bond and the reduction of N-acetyl groups produced films with a more compact and disordered structure, reducing their swelling characteristics and increasing their brittleness. The introduction of a mild NaOH treatment is a versatile tool to obtain chitosan films with interesting and tunable properties.

Quantitative analysis of mebendazole polymorphs in pharmaceutical raw materials using near-infrared spectroscopy.

This work evaluates the feasibility of using NIR spectroscopy for quantification of three polymorphs of mebendazole (MBZ) in pharmaceutical raw materials. Thirty ternary mixtures of polymorphic forms of MBZ were prepared, varying the content of forms A and C from 0 to 100% (w/w), and for form B from 0 to 30% (w/w). Reflectance NIR spectra were used to develop partial least square (PLS) regression models using all spectral variables and the variables with significant regression coefficients selected by the Jack-Knife algorithm (PLS/JK). MBZ polymorphs were quantified with RMSEP values of 2.37% w/w, 1.23% w/w and 1.48% w/w for polymorphs A, B and C, respectively. This is an easy, fast and feasible method for monitoring the quality of raw pharmaceutical materials of MBZ according to polymorph purity.

The influence of polymorphism on the manufacturability and in vitro dissolution of sulindac-containing hard gelatin capsules.

CONTEXT: Drug polymorphism could affect drug product dissolution, manufacturability, stability and bioavailability/bioequivalence. The impact of polymorphism on the manufacturability and in vitro dissolution profiles of sulindac capsules has not been studied yet. OBJECTIVE: To evaluate the impact of polymorphism on the manufacturability and in vitro dissolution of sulindac hard gelatin capsules. MATERIALS AND METHODS: Sulindac crystal forms I and II (SLDI and SLDII, respectively) were prepared and characterized. Powder formulations containing one of the polymorphs, lactose and magnesium stearate (at three different levels) were prepared and their flow properties determined. Hard gelatin capsules were filled with the formulations and tested for fill-weight variations. Drug dissolution for SLDI- and SLDII-containing hard gelatin capsules was determined. RESULTS: Differences in flow properties for each polymorph were observed, as well as for their formulations, which in turn affected capsule weight homogeneity. Statistically significant differences in the rate and extent of drug release were observed between SLDI- and SLDII-containing capsules. DISCUSSION: Formulations containing SLDI showed a better manufacturability and a better dissolution profile than those with SLDII. CONCLUSION: Sulindac crystalline form I was the best candidate for hard gelatin capsule formulation because of its technological and in vitro dissolution properties.

Structural analysis of the endogenous glycoallergen Hev b 2 (endo-ß-1,3-glucanase) from Hevea brasiliensis and its recognition by human basophils.

Endogenous glycosylated Hev b 2 (endo-ß-1,3-glucanase) from Hevea brasiliensis is an important latex allergen that is recognized by IgE antibodies from patients who suffer from latex allergy. The carbohydrate moieties of Hev b 2 constitute a potentially important IgE-binding epitope that could be responsible for its cross-reactivity. Here, the structure of the endogenous isoform II of Hev b 2 that exhibits three post-translational modifications, including an N-terminal pyroglutamate and two glycosylation sites at Asn27 and at Asn314, is reported from two crystal polymorphs. These modifications form a patch on the surface of the molecule that is proposed to be one of the binding sites for IgE. A structure is also proposed for the most important N-glycan present in this protein as determined by digestion with specific enzymes. To analyze the role of the carbohydrate moieties in IgE antibody binding and in human basophil activation, the glycoallergen was enzymatically deglycosylated and evaluated. Time-lapse automated video microscopy of basophils stimulated with glycosylated Hev b 2 revealed basophil activation and degranulation. Immunological studies suggested that carbohydrates on Hev b 2 represent an allergenic IgE epitope. In addition, a dimer was found in each asymmetric unit that may reflect a regulatory mechanism of this plant defence protein.

A polymorphic form of 4,4-dimethyl-8-methylene-3-azabicyclo[3.3.1]non-2-en-2-yl 3-indolyl ketone, an indole alkaloid extracted from Aristotelia chilensis (maqui).

The title compound [systematic name: (4,4-dimethyl-8-methylene-3-azabicyclo[3.3.1]non-2-en-2-yl)(1H-indol-3-yl)methanone], C20H22N2O, (II), was obtained from mother liquors extracted from Aristotelia chilensis (commonly known as maqui), a native Chilean tree. The compound is a polymorphic form of that obtained from the same source and reported by Watson, Nagl, Silva, Cespedes & Jakupovic [Acta Cryst. (1989), C45, 1322-1324], (Ia). The molecule consists of an indolyl ketone fragment and a nested three-ring system, with both groups linked by a C-C bridge. Comparison of both forms shows that they do not differ in their gross features but in the relative orientation of the two ring systems, due to different rotations around the bridge, as measured by the O=C-C=N torsion angle [130.0 (7)° in (Ia) and 161.6 (2)° in (II)]. The resulting slight conformational differences are reflected in a number of intramolecular contacts being observed in (II) but not in (Ia). Regarding intermolecular interactions, both forms share a similar N-H···O synthon but with differing hydrogen-bonding strength, leading in both cases to C(6) catemers with different chain motifs. There are marked differences between the two forms regarding colour and the (de)localization of a double bond, which allows speculation about the possible existence of different variants of this type of molecule.

O patenteamento de polimorfos na indústria farmacêutica e o acesso a medicamentos / The patenting of polymorphs in the pharmaceutical industry and access to medicines

Recentemente, as discussões sobre o patenteamento na área farmacêutica e seu impacto sobre o acesso da população aos medicamentos tem se intensificado, e, em 2008, o GIPI decidiu que patentes incrementais não deveriam ser concedidas no Brasil. Assim, neste trabalho, são discutidos os possíveis impactos dessas patentes para o acesso aos medicamentos, por meio do estudo do caso dos polimorfos. Como contribuição, a importância do patenteamento de polimorfos nas várias áreas tecnológicas foi estimada a partir dos depósitos no Brasil. Foi observado que mais de 70 por cento dos depósitos são da área farmacêutica. Estudos de casos foram feitos com dois fármacos: paroxetina e atorvastatina. A detentora do medicamento referência depositou cerca de metade dos pedidos para polimorfos da paroxetina. No caso da atorvastatina, embora a detentora do registro não seja o maior depositante, é ela quem reivindica o maior percentual de polimorfos. O estudo constatou que a indústria farmacêutica tem usado agressivamente as patentes como estratégia econômica, confirmando a preocupação do setor saúde sobre o acesso aos medicamentos.

Recently, discussions on patenting in the pharmaceutical area and its impact on people's access to drugs have intensified, and in 2008 the GIPI decided that the incremental patents should not be granted in Brazil. So this paper discusses the possible impacts of these patents on access to medicines through the case study of the polymorphs. As a contribution, the importance of patenting of polymorphs in various technology areas was estimated from the deposits in Brazil. It was observed that more than 70 percent of deposits are in the pharmaceutical area. Case studies were made with two drugs: atorvastatin and paroxetine. The holder of the reference drug deposited about half of the requests for polymorphs of paroxetine. In the case of atorvastatin, although the holder of the registration is not the largest depositor, who claims it is the highest percentage of polymorphs. The study found that the pharmaceutical industry has aggressively used patents as economic strategy, confirming the concern of the health sector on access to medicines.