Role of moisture on the physical stability of polymorphic olanzapine

Insight into the Manipulation Mechanism of Polymorphic Transformation by Polymers: A Case of Cimetidine

PURPOSE

Employing polymer additives is an effective strategy to realize the manipulation of polymorphic transformation. However, the manipulation mechanism is still not clear, which limit the precise selection of polymeric excipients and the development of pharmaceutical formulations.

METHODS

The solubility of cimetidine (CIM) in acetonitrile/water mixtures were measured. And the polymorphic transformation from CIM form A to form B with the addition of different polymers was monitored by Raman spectroscopy. Furthermore, the manipulation effect of polymers was determined based on the results of experiments and molecular simulations.

RESULTS

The solubility of form A is consistently higher than that of form B, which indicate that form B is the thermodynamically stable form within the examined temperature range. The presence of polyvinylpyrrolidone (PVP) of a shorter chain length could have a stronger inhibitory effect on the phase transformation process of metastable form, whereas polyethylene glycol (PEG) had almost no impact. The nucleation kinetics experiments and molecular dynamic simulation results showed that only PVP molecules could significantly decrease the nucleation rate of CIM, due to the ability of reducing solute molecular diffusion and solute-solute molecular interaction. A combination of crystal growth rate measurements and calculations of the interaction energies between PVP and the crystal faces of CIM indicate that smaller molecular weight PVP can suppress crystal growth more effectively.

CONCLUSION

PVP K16-18 has more impact on the stabilization of CIM form A and inhibition of the phase transformation process. The manipulation mechanism of polymer additives in the polymorphic transformation of CIM was proposed.

Probing fluconazole deposition inside mesoporous silica using solid-state NMR spectroscopy: Crystallization of a confined metastable form and phase transformations under storage conditions

Encapsulation of molecules into mesoporous silica carriers continues to attract considerable interest in the area of drug delivery and crystal engineering. Here, MCM-41, SBA-15 and MCF silica matrices were used to encapsulate fluconazole (FLU), a pharmaceutically relevant molecule with known conformational flexibility, using the melting method. The composites have been characterized using 1H, 13C and 19F NMR spectroscopy, nitrogen adsorption, PXRD and thermal analysis (DSC, TGA). Drug loading up to 50 wt% allowed us to probe the crystallization process and to detect different local environments of confined FLU molecules. 19F NMR spectroscopy enabled us to detect the gradual pore filling of silica with FLU and differentiate the amorphous domains and surface species. The use of the complementary structural and thermal techniques enabled us to monitor crystallization of the metastable FLU form II in MCF. Using 1H and 19F NMR spectroscopy we observed pore-size dependent reversible dehydration/hydration behaviour in the MCM and SBA composites. As water content has considerable importance in understanding of physicochemical stability and shelf-life of pharmaceutical formulations, experimental evidence of the effect of API-water-carrier interactions on the API adsorption mechanism on silica surface is highlighted.

Study on polycyclic macromolecular drug solid stability: A case exploration of methylcobalamin

As one of derivatives of Vitamin B12, methylcobalamin (MeCbl) is an indispensable "Life Element" and plays an essential role in maintaining human normal physiology function and clinical medicine application. Because of the intricate molecular structure, strong hygroscopicity and optical instability, maintaining its solid stability is a great challenge in pharmaceutical preparation. Based on the structure features of MeCbl hydrates, this study explored the drug solid stability by designing solid-solid phase transformation (SSPT) experiments. Three hydrate powders of MeCbl that had special structure with isolated site and channel water molecules were discovered. It was found that drying condition and surrounding humidity were controlling factors influencing the final solid form. The inter-conversion relations relevant to heating-induced and humidity-induced structure changes were established among the three hydrate powders. Powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, high performance liquid chromatography and dynamic vapor sorption were used to characterize the differences and related properties of stably prepared MeCbl hydrate powders. The particle size of product could be regulated and controlled by optimizing operating conditions of crystallization process, where ultrasound-assisted and seeding-introduced were applied as promising strategies to enhance solution crystallization process. This study opens up the possibility for the stable preparation and large-scale production of polycyclic macromolecular bulk drugs like methylcobalamin.

Solid-State Forms of Koumine Hydrochloride: Phase Transformations and the Crystal Structure and Properties of the Stable Form

To investigate the solid-state forms of koumine hydrochloride (KMY), solid form screening was performed, and one amorphous form and five crystalline forms (forms A, B, C, D, and E) were identified by powder X-ray diffraction. Form A was the dominant crystal product, and its crystal structure and packing pattern were determined by single-crystal X-ray diffraction. The crystals displayed an orthorhombic crystal system and symmetry of space group P2₁2₁2₁ with Z' = 1. The amorphous form transformed to form A at 105-120 °C or 75% RH, while forms B, C, D, and E could only be intermediate phases and readily transformed to form A at room temperature. Therefore, the phase transformations of KMY solid-state forms were established. The properties of the amorphous form and form A were further elucidated by applying vibrational spectroscopy, moisture sorption analysis, and thermal analysis. Accordingly, form A, the KMY anhydrate, was found to be the thermodynamically stable form with low hygroscopicity under ambient conditions. These characteristics are crucial in the manufacture and storage of active pharmaceutical ingredients.

Enhancing the stability of active pharmaceutical ingredients by the cocrystal strategy

Cocrystal strategies to achieve excellent physiochemical performance under different environmental stress were highlighted here. The lattice energy and the energy barrier of degradation reactions are two pillars in a stable cocrystal construction.

Challenges and opportunities of pharmaceutical cocrystals: a focused review on non-steroidal anti-inflammatory drugs

The focus of the review is to discuss the relevant and essential aspects of pharmaceutical cocrystals in both academia and industry with an emphasis on non-steroidal anti-inflammatory drugs (NSAIDs). Although cocrystals have been prepared for a plethora of drugs, NSAID cocrystals are focused due to their humongous application in different fields of medication such as antipyretic, anti-inflammatory, analgesic, antiplatelet, antitumor, and anti-carcinogenic drugs. The highlights of the review are (a) background of cocrystals and other solid forms of an active pharmaceutical ingredient (API) based on the principles of crystal engineering, (b) why cocrystals are an excellent opportunity in the pharma industry, (c) common methods of preparation of cocrystals from the lab scale to bulk quantity, (d) some latest case studies of NSAIDs which have shown better physicochemical properties for example; mechanical properties (tabletability), hydration, solubility, bioavailability, and permeability, and (e) latest guidelines of the US FDA and EMA opening new opportunities and challenges.

Crystal forms in pharmaceutical applications: olanzapine, a gift to crystal chemistry that keeps on giving

This contribution reviews the efforts of many scientists around the world to discover and structurally characterize olanzapine crystal forms, clearing up inconsistencies in the scientific and patent literature and highlighting the challenges in identifying new forms amidst 60+ known polymorphs and solvates. Owing to its remarkable solid-state chemistry, olanzapine has emerged over the last three decades as a popular tool compound for developing new experimental and computational methods for enhanced molecular level understanding of solid-state structure, form diversity and crystallization outcomes. This article highlights the role of olanzapine in advancing the fundamental understanding of crystal forms, interactions within crystal structures, and growth units in molecular crystallization, as well as influencing the way in which drugs are developed today.

Influence of crystal packing on the thermal properties of cocrystals and cocrystal solvates of olanzapine: insights from computations

A multicomponent supramolecular host with adaptive guest accommodation abilities is observed in the cocrystal solvates of the olanzapine–hydroquinone system.

Challenging identification of polymorphic mixture: Polymorphs I, II and III in olanzapine raw materials

Olanzapine (OLZ), a drug for the treatment of schizophrenia, presents in more than 60 crystal forms. Polymorphs I, II and III were reported, however, the preparation conditions for pure II and III have not been reported. Polymorph IV was reported but this form is actually polymorph II described at different temperature. The diversity of solid forms of OLZ, the change in the nomenclature found in the literature and the presence of polymorphic mixture in samples, increase the difficulty for a correct solid state characterization. Therefore, the goal was the polymorphic identification of three OLZ raw materials, highlighting the limitation of conventional techniques (typically used in analytical control) and the necessity to use a combination of advanced ones to solve this challenge. The samples were studied by conventional techniques such as powder X-ray diffraction, thermoanalytical techniques, infrared spectroscopy. In apart from that, synchrotron powder X-ray diffraction (SPXRD) and solid state nuclear magnetic resonance (ss-NMR) were used. All samples were in accordance with the pharmacopoeia criteria. However, the conventional techniques were not specific for the complete polymorphic identification. Therefore, a combination of advanced techniques (SPXRD and ss-NMR) was necessary to identify the mixture of polymorphs (I, II and III) in all samples.