Dehydration, hydration behavior, and structural analysis of fenoprofen calcium

Ultrasound-assisted theophylline polymorphic transformation: Selective polymorph nucleation, molecular mechanism and kinetics analysis

In this paper, the ultrasound-assisted solvent-mediated polymorphic transformation of theophylline was explored in detail. The induction time and reconstruction time were significantly decreased by ultrasound, thereby decreasing the total transformation time and promoting the transformation process. The ultrasound-promoted efficiency of nucleation was different in three alcoholic solvents, which was difficult to explain by traditional kinetic effects. To resolve the above confusion, binding energies calculated by Density Functional Theory were applied to explore the relationship between the ultrasound-promoted efficiency of nucleation and solute-solvent interactions. Then, a possible molecular self-assembly nucleation pathway affected by ultrasound was proposed: the ultrasound could change and magnify the crucial effect of the specific sites of solute-solvent interactions in the nucleation process. Finally, the transformation kinetics with different effective ultrasonic energies was quantitatively analyzed by Avrami-Erofeev model, indicating that the dissolution element in the rate-limiting step was gradually eliminated by higher ultrasonic energy. Fortunately, the elusive crystal form V could be easily obtained by the ultrasound-assisted polymorph transformation. This proved to be a robust method to produce high purity form V of theophylline. The outcome of this study demonstrated that the proper ultrasonic irradiation had the potential to produce specific polymorphs selectively.

Optimizing the morphology of calcium d-pantothenate by controlling phase transformation processes

A process for preparing calcium d-pantothenate tetramethanol monohydrate (d-PC·4MeOH·H₂O) with a block-like morphology was developed, the solvent-free D-PC with a block-like morphology was obtained by controlling the de-solvation of d-PC·4MeOH·H₂O.

A peculiar dehydration and solid–solid phase transition of the active pharmaceutical ingredient AZD9898 based on in situ single crystal-to-single crystal transformations

Isostructural dehydration from form A hydrate to form B, and solid–solid phase transition from form B to C of AZD9898 were revealed by in situ single crystal-to-single crystal transformations.

Synthesis of a molecularly imprinted polymer and its application in selective extraction of fenoprofen from wastewater

The presence of various classes of pharmaceutical drugs in different environmental compartments has been reported worldwide. In South Africa, the detection of pharmaceuticals especially the non-steroidal anti-inflammatory drugs is recent, and more studies are being done in order to fully understand their fate in the aquatic environment. With considerations for the need of better sample preparation techniques, this study synthesized a molecularly imprinted polymer for the selective extraction of a non-steroidal anti-inflammatory drug, fenoprofen in aqueous environmental samples. Batch adsorption studies showed that adsorption of fenoprofen onto the cavities of the polymer followed a Langmuir isotherm as well as a pseudo second order model implying formation of a monolayer on the surface through chemisorption. The polymer had a maximum adsorption capacity of 38.8 mg g^-1 and a Langmuir surface area of 1607 m² g^-1. The imprinted polymer was then used as the selective sorbent for solid phase extraction in the analysis of fenoprofen from wastewater followed by chromatographic determination. The analytical method gave a detection limit of 0.64 ng mL^-1 and recovery of 99.6%. The concentration of fenoprofen detected in influent and effluent samples from two wastewater treatment plants ranged from 24 to 58 ng mL^-1. The ability of the treatment plants to remove fenoprofen during wastewater processing based on the difference in concentrations in influent and effluent samples was found to be 41%. This work has shown that there is a possibility of release of fenoprofen from wastewater treatment plants into surface water sources.

Hollow crystal generation through polymorphic transformation – a case study of flufenamic acid

Identification of mechanism behind hollow crystal forming ability of drugs.

Effect of Polymers on the Physicochemical Properties and Biological Performance of Fenoprofen Calcium Dihydrate-Triacetyl-β-Cyclodextrin Complex

BACKGROUND

Fenoprofen calcium dehydrate (FCD) is counted as a non-steroidal, anti-inflammatory, anti-arthritic drug. FCD is slightly water soluble. It is indicated for mild pain relief, where the suggested dosage is 200 mg orally every 4 to 6 h.

AIM

Reduce dissolution efficiency, reach an extended therapeutic effect and reduce the frequency of the drug side effects.

METHOD

Combination of the co-evaporated drug:triacetyl-β-cyclodextrin complex prepared in a ratio of 1:3 and either of two polymers-hydroxylpropylmethyl cellulose (HPMC) or ethyl cellulose (EC)-in the same formulation. Invitro dissolution studies were carried in simulated gastric (pH 1.2) and intestinal (pH 6.8) fluids, by using the USP dissolution tester (rotating paddle apparatus). The FCD in vitro release from EC/drug complex was markedly retarded. Interaction between fenoprofen, TA-β-CD, EC, HPMC in the solid state were confirmed by FT-IR, DSC, XRD and SEM. In vivo studies assessed the anti-inflammatory and analgesic activities and the results were compared with the market product Nalfosab® Capsules.

RESULTS

Remarkable inhibition of inflammation and nociception after 24 h was attained for EC/drug complex.

CONCLUSIONS

EC/drug complex has a sustained effect due to high remaining amount after elapsing with remarkable inhibition of inflammation.

Liquid Crystal Systems in Drug Delivery

Liquid crystals have been recently studied as novel drug delivery system. The reason behind this is their similarity to colloidal systems in living organisms. They have proven to be advantageous over Traditional, Dermal, Parentral and Oral Dosage forms. Liquid crystals are thermodynamically stable and possess long shelf life. Liquid crystals show bio adhesive properties and sustained release effects. Objective of this book chapter is to provide in-depth information of Pharmaceutical crystal technology. It shall deal with cubic and hexagonal liquid crystal and their applications in Drug delivery system.

The solid-state continuum: a perspective on the interrelationships between different solid-state forms in drug substance and drug product

Objective

The objective of the review is to provide an overview of the nomenclature used in the solid-state continuum and relate these to the development of drug substances and drug products.

Key findings

The importance of a rational approach to solid-state form selection, including integrated decision making (ensuring equal weight is given to the needs of the drug substance and the drug product), is vital for the effective development of a drug candidate. For example, how do secondary processing considerations influence the selection of drug substance solid-state form and resulting formulation, and how can drug substance solid-state form be used to optimise secondary processing? Further, the potential use of ‘crystal’ engineering to optimise stability, purity and optical resolutions, and the linked regulatory requirements, will be discussed.

Summary

The nomenclature used in the solid-state continuum, which contains a large number of different crystalline and non-crystalline forms, for example, amorphous systems, was reviewed. Further, the significant role of the drug substance within the solid oral dose form from a physicochemical perspective was covered.

Dehydration Process of Hofmann-Type Layered Solids

In the present work the dehydration process of layered solids with formula unit M(H₂O)₂[Ni(CN)₄]·nH₂O, M = Ni, Co, Mn; n = 1, 2, 4 is studied using modulated thermogravimetry. The results show that water molecules need to overcome an energetic barrier (activation energy between 63 and 500 kJ/mol) in order to diffuse through the interlayer region. The related kinetic parameters show a dependence on the water partial pressure. On the other hand, X-ray diffraction results provide evidence that the dehydration process is accompanied by framework collapse, limiting the structural reversibility, except for heating below 80 °C where the ordered structure remains. Removal of water molecules from the interlayer region disrupts the long-range structural order of the solid.

Use of pharmaceutical salts and cocrystals to address the issue of poor solubility

Salt and cocrystal formation are the most commonly used method of increasing solubility and dissolution rate of pharmaceutical compounds, and are of particular interest for compounds with an intermediate to low aqueous solubility. However, selection of the most appropriate form does not necessarily equate to selection of the salt/cocrystal with the optimal aqueous solubility, but rather a balance between the best solubility and the best physicochemical properties. This review provides a presentation of salt and cocrystal selection, from a high throughput screening perspective and then an assessment of counter ion properties, common ion effects and the potential impact on the biopharmaceutical performance of the compound. In addition, there is a brief discussion of the impact on polymorphism, the potential use of salts and stoichiometric amorphous mixtures to stabilise amorphous forms and other potential issues for consideration from a pharmaceutical development perspective.

Tetra-kis[μ-2-(3-phenoxy-phen-yl)propionato-κO:O']bis-[(dimethyl-formamide-κO)copper(II)]

The title compound, [Cu(2)(C(15)H(13)O(3))(4)(C(3)H(7)NO)(2)], is formed by the chelate coordination of four racemic fenoprofenate (fenoprofenate is 2,3-phenoxyphenyl propionate) anions and two dimethyl-formamide mol-ecules to two copper(II) ions, building a paddle-wheel dinuclear mol-ecule. The distorted square-pyramidal coordination of each Cu(II) atom is made up of four O atoms of the four fenoprofenate units and another O atom from a dimethyl-formamide mol-ecule. The two enanti-omeric forms of the fenoprofenate anions are present in the complex, in an optically inactive centrosymmetric arrangement.

Dehydration behavior and structural characterization of the GW275919X monohydrate

GW275919X, a central muscle relaxant for the treatment of lower back pain, exists in a monohydrate. Knowledge of the solid state dehydration behavior and the crystal structure is essential for determining its relative physical stability. Thermal analysis and hot-stage powder X-ray diffraction were used to study the solid state phase transformation during the dehydration process. Crystal structure was determined by single crystal X-ray analysis. Molecular modeling with Cerius(2) software was used to visualize the hydrate crystal structure and to construct the molecular packing and hydrogen bond diagram. Morphology prediction was performed using the BFDH calculation. Crystallographic data: monoclinic, space group, P21/c, a (Angstrom)=14.3734, b (Angstrom)=5.0336, c (Angstrom)=15.4633 and beta=105.11 degrees. Water molecules in the hydrate crystal of GW275919X are involved in the hydrogen bonds and these hydrogen bonds contribute to the coherence of the crystal structure. The longest dimension of the predicted morphology is in the b-direction, which would correspond to the needle axis of the experimental crystals.

Structure and Physical Stability of Hydrates and Thermotropic Mesophase of Calcium Benzoate

The aim of this study is to investigate the hydration and the dehydration processes of calcium benzoate hydrates (trihydrate and monohydrate), thermotropic mesophases (dehydrated mesophase and lyophilized mesophase) and amorphous state, and the influence of their molecular order on those processes. X-ray analysis revealed that trihydrate has a planar structure composed of two types of planes-one from benzoic acid, water, and calcium ion and another from benzoic acid and water-and that both planes are linked by three water molecules. It was found that calcium benzoate was able to exist as thermotropic mesophases by dehydration of trihydrate and lyophilization. These mesophases were characterized by polarizing-light microscopy (PLM), X-ray powder diffraction (XRPD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Both mesophases prepared by two procedures showed some similar physical properties, but lyophilized mesophase seemed to have molecular structure with higher order than dehydrated mesophase. The mesophases exhibited different hydration behavior. The dehydrated mesophase showed a stepwise rehydration process where it became monohydrate first and then trihydrate. The lyophilized mesophase became trihydrate without appearance of monohydrate. An amorphous form could also be prepared and it rehydrated first to the monohydrate and then trihydrate. The results suggest that the more disordered dehydrated mesophase and amorphous state change to monohydrate whereas the more ordered lyophilized mesophase cannot change to monohydrate but only to trihydrate.

Pharmaceutical liquid crystals: the relevance of partially ordered systems

Pharmaceutical solids have generally been characterized as either three-dimensional crystals or amorphous solids based on X-ray powder diffraction and modulated temperature differential scanning calorimetry. In contrast, fewer examples of thermotropic and lyotropic liquid crystals, or mesophases, appear in the pharmaceutical literature, and that literature teaches that the aforementioned analytical techniques should be complemented with polarized light microscopy and small-angle X-ray scattering in order to effectively identify potential liquid crystalline states. Lyotropic liquid crystals are induced by the presence of solvent, and have been extensively described elsewhere in the context of emulsion technology; however, other pharmaceutical examples are emerging. Thermotropic liquid crystals are induced by a change in temperature and are essentially free of solvent, where more pharmaceutical applications appear in the literature. In the present review the general structural characteristics that favor the formation of liquid crystalline mesophases are categorized by therapeutic target and molecular size, and the analytical means of their identification are presented.

Characterization of dehydration and hydration behavior of calcium lactate pentahydrate and its anhydrate

The use of calcium lactate pentahydrate (CLP) as an additional filler-binder for direct compaction of tablets has been reported to result in a short disintegration time and rapid drug release. The aim of this study was to understand the dehydration and hydration behavior of CLP and calcium lactate anhydrate (CLA) under various conditions of storage temperature and relative humidity. The removal and acquisition of crystal water were investigated by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The PXRD results indicated that CLP exists as a crystalline solid and CLA as an amorphous solid. Dehydration of CLP resulted in aggregated particles of CLA with an increase in average particle size. The dehydration and hydration kinetics of CLP were analyzed with the Hancock-Sharp equation on the basis of the isothermal DSC data. The dehydration of CLP followed a zero-order mechanism (Polany-Winger equation). In contrast, the surface roughness of CLA was significantly decreased by hydration. The hydration of CLA followed a three-dimensional diffusion model (Ginstling-Brounshtein equation).