The action of colloidal silicon dioxide as a glidant for lactose, paracetamol, oxytetracycline and their mixtures

Charge Reduction Assisted Production of Diminutive Fluid Bed Granules for High Drug Load Minitablets

Micronized drug powders are generally unsuitable as tableting feed to produce minitablets due to their cohesivity and poor flow. The silicification of fine paracetamol powder (PCM_F) with an optimal concentration range of fumed silica (fSi) [0.7 - 0.9 %, w/w] reduced the net negative charge of PCM_F and improved powder flow. The optimal fSi concentration range suitable was established through the measurement of charge and flowability of the silicified powders. Silicification of PCM_F by physical mix did not satisfactorily overcome the cohesive forces between the PCM_F crystals and improve powder flow sufficiently such that it will feed consistently into the smaller die orifices during tableting. Using a specialized fluid bed system with swirling air and side spray, controlled granulation of silicified PCM_F packed and agglomerated the interlocking-prone needle shaped PCM_F crystals into diminutive granules that are more spherical and free flowing. With optimized fSi concentration (≈ 0.8 %, w/w) and granulation process parameters, high drug load diminutive granules (D₅₀≃ 90 μm) were successfully prepared from PCM_F as starter seeds (D₅₀≃ 30 μm). Minitablets prepared from the diminutive granules had low weight variation, and were mechanically strong with disintegration time of less than 30 s. This study demonstrated the feasibility of producing high drug load minitablets from a cohesive, electrostatic-prone fine drug powder.

Compression of amorphous solid dispersions prepared by hot-melt extrusion, spray drying and vacuum drum drying

The present study explored vacuum drum drying (VDD) as an alternative technology for amorphous solid dispersions (ASDs) manufacture compared to hot-melt extrusion (HME) and spray drying (SD) focusing on downstream processability (powder properties, compression behavior and tablet performance). Ritonavir (15% w/w) in a copovidone/sorbitan monolaurate matrix was used as ASD model system. The pure ASDs and respective tablet blends (TB) (addition of filler, glidant, lubricant) were investigated. Milled extrudate showed superior powder properties (e.g., flowability, bulk density) compared to VDD and SD, which could be compensated by the addition of 12.9% outer phase. Advantageously, the VDD intermediate was directly compressible, whereas the SD material was not, resulting in tablets with defects based on a high degree of elastic recovery. Compared to HME, the VDD material showed superior tabletability when formulated as TB, resulting in stronger compacts at even lower solid fraction values. Despite the differences in tablet processing, tablets showed similar tablet performance in terms of disintegration and dissolution independent of the ASD origin. In conclusion, VDD is a valid alternative to manufacture ASDs. VDD offered advantageous downstream processability compared to SD: less solvents and process steps required (no second drying), improved powder properties and suitable for direct compression.

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ASD technology has influence on particle morphology

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Compression behavior dominated by particle morphology

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Vacuum drum dried intermediate direct compressible into tablets

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Vacuum drum dried material shows better tabletability as milled extrudate

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ASD technology: no impact on tablet disintegration/dissolution

On the mechanism of colloidal silica action to improve flow properties of pharmaceutical excipients

The mechanism of colloidal silica action to improve flow properties of pharmaceutical powders is known to be based on inter-particle force disruption by silica particles adhered to the particle surface. In the present article, the kinetic aspects of this action are investigated, focusing on non-spherical particles of different size. Blends comprising microcrystalline cellulose or calcium hydrogen phosphate dihydrate and colloidal silica were examined using powder rheometer. The blends were formulated to represent effects of particle size, surface texture, colloidal silica loading, and mixing time. Pre-conditioning, shear testing, compressibility, and flow energy measurements were used to monitor flow properties. Components and blends were analyzed using particle size analysis and scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS) and back-scattered electron (BSE) detection to determine surface particle arrangement. All studied parameters were found to have substantial effects on flow properties of powder blends. Those effects were explained by identifying key steps of colloidal silica action, which were found to proceed at substantially different rates, causing the flow properties change over time being dependent on the blend formulation and the component properties.

Investigating the effects of excipients on the powder flow characteristics of theophylline anhydrous powder formulations

Pharmaceutical excipients may have a great effect on properties affecting tablet production. To determine if formulations containing theophylline anhydrous would have properties allowing them to be easily tableted, functional parameters affecting powder flow were evaluated. The Carr Flowability Indices were used for this evaluation. Formulations to be studied include theophylline anhydrous as the active ingredient, hydrous lactose and dicalcium phosphate dihydrate as diluents, polyvinylpyrrolidone as a binder, and fumed silica as a flow promoter. The effect of each component on powder flow is discussed.

Design and validation of an annular shear cell for pharmaceutical powder testing

An annular shear cell was constructed for powder flow testing, the influence of design and process parameters was characterized, and the results were compared with other flow methods. The shear cell was designed with interchangeable parts to mimic other shear cells. The texture of the powder-metal interface and the gap distance between the lid and side wall of the trough were varied, and the effects of shear rate, powder bed thickness, and consolidation times were tested. Shear parameters, such as cohesion, angles of friction, and flow factors, were measured for microcrystalline cellulose, anhydrous lactose, spray-dried lactose, mannitol, dibasic calcium phosphate dihydrate, anhydrous theophylline, and theophylline monohydrate powder. The results were then compared with the Carr index, mass flow rate, and flowability index. Design parameters such as surface texture and the gap distance significantly affected the shear call results, whereas for the process parameters studied, the shear rate, consolidation time, and powder bed height had a minimal effect on the shear cell results. Of the shear parameters obtained, the angles of friction best represented the known flow properties of powders and were in general agreement with those from other flow tests.

Food applications and the toxicological and nutritional implications of amorphous silicon dioxide

The chemical and physical characteristics of the different types of amorphous silicon dioxide contribute to the versatility of these compounds in a variety of commercial applications. Traditionally, silicas have had a broad spectra of product usage including such areas as viscosity control agents in inks, paints, corrosion-resistant coatings, etc. and as excipients in pharmaceuticals and cosmetics. In the food industry, the most important application has been as an anticaking agent in powdered mixes, seasonings, and coffee whiteners. However, amorphous silica has multifunctional properties that would allow it to act as a viscosity control agent, emulsion stabilizer, suspension and dispersion agent, desiccant, etc. The utilization of silicas in these potential applications, however, has not been undertaken, partially because of the limited knowledge of their physiochemical interactions with other food components and partially due to their controversial status from a toxicological point of view. The main goal of this review is to compile current information on the incorporation of amorphous silicon dioxide as a highly functional and viable additive in the food processing industry as well as to discuss the most recent toxicological investigations of silica in an attempt to present some of the potential food applications and their concomitant toxicological implications. Some of the more significant differences between various silicas and their surface chemistries are presented to elucidate some of their mechanisms of interaction with food components and other biological systems and to aid in the prediction of their rheological or toxicological behavior.