On the mechanisms of formation of spherical agglomerates

Enabling the drug combination of celecoxib through a spherical co-agglomeration strategy with controllable and stable drug content and good powder properties

Combining celecoxib with other chemopreventive drugs is a promising method of chemoprevention for cancer, especially for colorectal cancer. However, the traditional drug combination approaches are restricted with high-cost apparatus, complex and numerous unit operations. This work aims to develop an efficient spherical co-agglomeration strategy for celecoxib in combination with lovastatin, which can achieve drug combination in a single crystallization unit. The ternary solvent system was determined based on molecular simulation, and then a stable spherical agglomeration process was developed through the design of molar fraction of anti-solvent (MFA) and stirring rate to produce spherical agglomerates with high sphericity (84.2-89.9 %) and narrow size distribution. On this basis, celecoxib-benzoic acid spherical co-agglomerates were designed to form a complete spherical co-agglomeration strategy, which includes solvent system selection, spherical agglomeration and spherical co-agglomeration. Finally, celecoxib-lovastatin spherical co-agglomerates with synergistic efficacy were successfully produced by this strategy, with controllable and stable drug content (fluctuation < 2.7 %), good powder properties, and improved tabletability.

Development of piroxicam mini-tablets enabled by spherical cocrystallization

We examined the potential of the spherical cocrystallization (SCC) technology in simultaneously enhancing tablet manufacturability and dissolution of poorly soluble drugs by developing a mini-tablet formulation of piroxicam. The manufacturing of mini-tablets using a direct compression (DC) process is more challenging than conventional tablets because of the much stricter requirement on the micromeritic properties of formulated powders. The SCC process in this work involved two steps: 1) preparing a new piroxicam-ferulic acid (PRX-FA) cocrystal, and 2) forming spherical agglomerates with the aid of a suitable bridging liquid. The PRX-FA cocrystal exhibited enhanced solubility as well as improved plasticity. The bridging liquid, a mixture of chloroform and ethyl acetate (EA) (1: 2, v/v), was chosen based on the high computed adsorption energy of chloroform and EA on morphologically dominating crystal faces of PRX-FA. The improved flowability, tabletability, and dissolution rate of spherical PRX-FA enabled the successful development of a DC mini-tablet formulation with a high PRX loading (41 wt%). This example shows that SCC is a powerful enabling technology for DC tablet formulation development of challenging drugs.

Simple and Efficient Spherical Crystallization of Clopidogrel Bisulfate Form-I via Anti-Solvent Crystallization Method

Clopidogrel bisulfate (CLP) form-I crystals are irregular, rectangular-shaped crystals. Because of their poor compressibility, flowability and their strong surface tension, manufacturers apply spherical crystallization methods to produce CLP form-I spherical agglomerates with a uniform particle size distribution. Consequently, manufacturers primarily synthesize CLP form-I crystal salts utilizing very complex methods, which produces form-I spherical agglomerates by means of spherical crystallization. In this study, spherical crystals of CLP Form-I were directly prepared from CLP Form-II, the most stable polymorph at room temperature, by using ethanol as solvent and a mixture of isopropyl alcohol (IPA)/n-Hexane (Hex) as an anti-solvent. To provide systematic inputs for the development of spherical agglomerates of optimal morphology, size, particle size distribution (PSD), and polymorphic form, processing parameters such as anti-solvent type, a mixture of IPA/Hex, pure Hex, or pure acetone; stirring speeds of 500, 600, 700, or 800 rpm; and temperatures ranging from 25 to 40 °C were explored. The effects of these parameters on spherical crystallization and polymorphic form were studied in terms of supersaturation, a driving force for polymorphic transformation, and the crystallization solution. Notably, our method does not require a large volume of anti-solvent which is the main complication of conventional anti-solvent crystallization methods.

l-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity

A new polymorph and twisted semi-spherulites ofl-malic acid are described and discussed in this work.

Evaluation of the effect of some additives on the efficiency of binder liquid in wet agglomeration of crystals

OBJECTIVE

Wet agglomeration is a process wherein dispersed particles are held together in an aggregated form by the presence of a small quantity of solvent which acts as binder liquid. In this work, the efficiency of binder liquid was tested in the presence of various additives.

METHODS

Solid state of carbamazepine (CBZ) agglomerates was characterized by DSC and FT-IR. The obtained agglomerates were also investigated in terms of yield, size distribution, friability, and drug release.

RESULTS

CBZ agglomerates formed only in the presence of talc, span, and croscarmellose sodium (CCS), whereas ethyl cellulose and eudragit RS100 failed to make CBZ agglomerates. The presence of talc decreased the agglomerate size and produced CBZ agglomerates with a poor strength. However, span and CCS led to larger agglomerates with superior strength. In contrast to CCS samples, span and talc altered the dissolution rate of CBZ. FT-IR results showed that there is an interaction between CCS and drug.

CONCLUSION

This study suggests that care must be taken when additives are used to manufacture agglomerates as the type of additives even in low concentrations can have a big impact on the efficiency of the binder liquid in forming agglomerates thereby affecting the quality of agglomerates.

Effect of binder liquid type on spherical crystallization

AIM

Spherical crystallization is a process of formation of agglomerates of crystals held together by binder liquid. This research focused on understanding the effect of type of solvents used as binder liquid on the agglomeration of crystals.

METHOD

Carbamazepine and ethanol/water were used respectively as a model drug and crystallization system. Eight solvents as binder liquid including chloroform, dichloromethane, isopropyl acetate, ethyl acetate, n-hexane, dimethyl aniline, benzene and toluene were examined to better understand the relationship between the physical properties of the binder liquid and its ability to bring about the formation of the agglomerates. Moreover, the agglomerates obtained from effective solvents as binder liquid were evaluated in term of size, apparent particle density and compressive strength.

RESULTS

In this study the clear trend was observed experimentally in the agglomerate formation as a function of physical properties of the binder liquid such as miscibility with crystallization system. Furthermore, the properties of obtained agglomerates such as size, apparent particle density and compressive strength were directly related to physical properties of effective binder liquids.

CONCLUSION

RESULTS of this study offer a useful starting point for a conceptual framework to guide the selection of solvent systems for spherical crystallization.

Preparation and evaluation of agglomerated crystals by crystallo-co-agglomeration: an integrated approach of principal component analysis and Box-Behnken experimental design

Poor mechanical properties of crystalline drug particles require wet granulation technique for tablet production which is uneconomical, laborious, and tedious. The present investigation was aimed to improve flow and mechanical properties of racecadotril (RCD), a poorly water soluble antidiarrheal agent, by a crystallo-co-agglomeration (CCA) technique. The influence of various excipients and processing conditions on formation of directly compressible agglomerates of RCD was evaluated. Principal component analysis and Box-Behnken experimental design was implemented to optimize the agglomerates with good micromeritics and mechanical properties. The overall yield of the process was 88-98% with size of agglomerates between 351 and 1214 μm. Further, higher rotational speed reduced the size of agglomerates and disturbed sphericity. The optimized batch of agglomerates exhibited excellent flowability and crushing strength. The optimized batch of RCD agglomerates was characterized by fourier transform infrared spectroscopy, differential scanning calorimetry, powder X-ray diffractometry and gas chromatography which illustrated absence of drug-excipient interaction with minimal entrapment of residual solvent. Hence, it may be concluded that both excipients and processing conditions played a vital role to prepare spherical crystal agglomerates of RCD by CCA and it can be adopted as an excellent alternative to wet granulation.

Spherical crystallization of drugs

Spherical crystallization of drugs is the process of obtaining larger particles by agglomeration during crystallization. The most common techniques used to obtain such particles are spherical agglomeration and quasi-emulsion solvent diffusion. Ammonia diffusion systems and crystallo-co-agglomeration are extensions of these techniques. By controlling process parameters during crystallization, such as temperature, stirring rate, type and amount of solvents, or excipient selection, it is possible to control the formation of agglomerates and obtain spherical particles of the desired size, porosity, or hardness. Researchers have reported that the particles produced have improved micromeritic, physical, and mechanical properties, which make them suitable for direct compression. In some cases, when additional excipients are incorporated during spherical crystallization, biopharmaceutical parameters including the bioavailability of drugs can also be tailored.

How spherical crystallization improves direct tableting properties: a review

Direct tableting has been renewed as a preferable process by simply mixing and compressing powder to save time and cost in comparison with granule tableting. Direct compression tableting as a technique has been successfully applied to numerous drugs on the industrial scale, although the success of any procedure, and resulting mechanical properties of tablets, is strongly affected by the quality of the crystals used. Good flowability, packability and compactability are prerequisite for drug to be prepared by direct tableting. When the mechanical properties of the drug particles are inadequate a primary granulation is necessary. The use of spherical crystallization as a technique appears to be an efficient alternative for obtaining suitable particles for direct tableting. Spherical crystallization is a particle design technique, by which crystallization and agglomeration can be carried out simultaneously in one step and which has been successfully utilized for improvement the micromeritic properties of crystalline drugs. In this review, we will discuss how the micromeritic properties of the particles such as flowability, packability and compactability can be improved by spherical crystallization technique.