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Browsing by Subject "magnesiumstearaatti"

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  • Koskela, Jaana (2015)
    Mechanofusion is a dry coating method in which the high shear forces cause a mechanochemical reaction between the processed particles. With the approach it is possible to improve flowability of a host cohesive powder when the guest particle forming the coating is magnesium stearate. Applying mechanofusion in tablet formulations could make poor flowing large dose drug substances suitable for direct compression. However, it is well known that magnesium stearate decreases mechanical strength of the tablets and prolongs disintegration and dissolution time of tablets. A previous study, however, showed that it is possible to compress tablets from a formulation dry coated with magnesium stearate without reducing the dissolution rate. Dry coating with magnesium stearate and its effect on a plastic material, known to be sensitive for the negative effects of magnesium stearate, has not been studied previously. The aim of the study was to examine the effect of mechanical dry coating with magnesium stearate on the physical qualities and compression behaviour of a plastic material. The effect was studied by dry coating four grades of microcrystalline cellulose with different magnesium stearatecon centrations. The approach was to find an optimum between the flowability and compressibility of the powders by using different process parameters. Microcrystalline cellulose with median particle size of 23 and 78 µm were also mechanofused without magnesium stearate in order to examine whether mechanofusion itself has an effect on the properties of microcrystalline cellulose. Pure raw materials and Turbula-mixed magnesium stearate and microcrystalline cellulose blends were studied as references. Dry coating with magnesium stearate improved the flow properties of microcrystalline cellulose with D50 value less than 78 µm. Powders with D50 value greater than 144 µm, however, break down under the shear during the process and hence their flow properties were decreased. This suggests, that mechanofusion as a process is more suitable for the small particle size microcrystalline cellulose powders which, based on the results, can withstand the high-shear forces better. Mechanofusion of plain microcrystalline cellulose (D50 78 µm) revealed that the moisture content of the powder increased and stronger tablets could be compressed. Mechanofusion may cause changes to the microstructure of microcrystalline cellulose particles and to its ability to adsorb moisture. Dry coating with magnesium stearate was very effective even with short processing times and relatively low blade speeds, and it was challenging to compress hard tablets from the mechanofused mixtures. Plastic material was found to be sensitive for the negative effects of magnesium stearate, and better flow properties of a mechanofused powder resulted in weaker compressed tablets.
  • Viskari, Ansa (2012)
    The purpose of this study was to investigate how the mixing time of the magnesium stearate affects on the compressibility of partially pregelatinized maize starch. Pregelatinized maize starch is used in pharmaceuticals as a filler, binder and as disintegrant. Because pregelatinized maize starch has lubricant characteristics itself, it is known to be sensitive for the amount and the mixing time of magnesium stearate. The aim is that magnesium stearate is not totally homogenously mixed on the powder surfaces so that even, clean powder surfaces exist. Homogeneous mixing means that particles are coated with magnesium stearate, which as a hydrophobic ingredient prevents bond formation between plastically and elastically behaving particles. Too much magnesium stearate and/or too long mixing time may cause weakening of tablet tensile strength, laminating and capping. The weakening of the tensile strength of the tablet increases friability, which causes problems during packaging process and the transportation. Too much magnesium stearate may also lengthen the disintegration time and slow down the dissolution. The aim of this study was to compare four different brands of pregelatinized maize starch. The purpose was to find differences affecting the compressibility behavior. Also the effect of the mixing time of magnesium stearate for compression behavior of masses were studied. The brands investigated were C*PharmGel DC 93000, Lycatab® C, Starch 1500® and SuperStarch 200®. First mentioned was a reference product which is not manufactured any more. There was only one batch of the reference product but three batches from other products to be able to investigate also batch to batch variation. The characteristics studied from pregelatinized starch samples were bulk density, apparent density and true density, flowability, moisture sorption, moisture content, pH value, swelling volume and particle size. Also NIR, FTIR and Raman spectroscopy and X-ray powder diffraction method were used. Weight, tensile strength, dimensions, friability, disintegration time and moisture sorption were studied for tablets. The compressibility of the mass and elastic behavior of tablets was studied. Pictures of the tablets were also taken by scanning electron microscope. When the mixing time of magnesium stearate was increased from 2 minutes to 5 minutes, the compression pressure needed for pressing tablets for 80 N strength increased 200-700 N depending on the brand of pregelatinized maize starch. Based on the results the best alternative to replace C*PharmGel DC 93000 was chosen to be SuperStarch 200®. Scanning electron microscope pictures showed that C*PharmGel DC 93000 deviates from other qualities studied by being roundish and regular in shape. SuperStarch 200® and Starch 1500® reminded remarkably each other. Lycatab® C was the biggest in particle size and very irregular in shape. The differences found in tabletting followed the expectations based on the SEM-pictures. SuperStarch 200® showed to best compressibility in lowest strain strength and after C*PharmGel DC 93000 it was least sensitive for mixing time of the magnesium stearate. It also has least elastic recovery. The differences between SuperStarch 200® and Starch 1500® in compression properties were moderate but clear. Lycatab® C had clearly the weakest compression properties.