3/14/2023 0 Comments Heating iunit stabilizers![]() Studies have shown that drugs crystallized by this method can not only have improved flowability ( 11), but also an improved tabletability ( 12, 13), reduced punch-sticking ( 14), storage agglomeration ( 11) and improved dissolution rates ( 15). ![]() The counter-diffusion of the solvents into and out of the quasi-emulsion droplets leads to an increase of the saturation within, which eventually leads to the formation of a crust and spherical, hollow agglomerates. QESD crystallizations are typically based on antisolvent crystallizations where surfactants are used to create a transient emulsion of the solute solution within the antisolvent. The quasi-emulsion solvent-diffusion (QESD) crystallization method is a type of spherical crystallization alongside the spherical agglomeration and ammonia-diffusion method. During typical crystallizations, such as cooling, evaporation or antisolvent addition, particle size and morphology can be influenced by, e.g., the super saturation ( 8), agitation rate ( 9) or choice of solvent ( 10). Many drugs form needles or other poorly flowing crystal structures, so that further processing, like granulation or spray-drying, or the addition of glidants is required to produce a free-flowing powder.Īs the crystallization of an API or excipient is often part of the final production step, using a crystallization method which can favorably change the micromeritic properties of the product is advantageous. Different product attributes, such as residual moisture ( 1, 2), particle size distribution ( 3, 4, 5), particle morphology ( 4, 5) and electrostatic charging ( 6, 7) can affect the flowability of powders. Good flowability of powders can be essential for further processing, to ensure, for example, a homogenous blending process and reproducible filling of the die during tableting. Furthermore, QESD crystallizations seem to be more robust when the stabilizer is dissolved in the antisolvent, however this can lead to a reduced drug load of the agglomerates. More polymers could be used to stabilize the transient emulsion of celecoxib than previously found in literature. For MF, the type of hypromellose used can have a significant influence on the properties of the agglomerates. QESD crystallizations of metformin hydrochloride (MF) and celecoxib showed that the type of stabilizer and whether it is dissolved in the solvent or antisolvent has an effect on the agglomerates. The dynamic viscosities of a low-viscosity grade hypromellose solution used in the previous publications describing the QESD crystallization of metformin hydrochloride by the authors was used as a target value. To gain further understanding for the role of the stabilizer, a new screening-method was developed which compared different surface active polymers in solution at similar dynamic viscosities rather than at a set concentration. Surfactants, such as surface-active polymers like hypromellose, are often required to stabilize the quasi-emulsion. Within the droplets the material can crystallize and agglomerate into spherical, hollow particles. Spherical particles are generated by dispersing a solvent phase in an antisolvent so that a transient emulsion is formed. Quasi-emulsion solvent-diffusion crystallization (QESD) is a type of spherical crystallization which can be used as a particle design method to improve the flowability and micromeritic properties of drugs or excipients.
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