Glidants silicon dioxide

Excipients play a key role in oxidation, either as a primary source of oxidants, trace amounts of metals, or other contaminants. Auto-oxidation of diethylstilbes-terol to the peroxide and conjugated quinone degradation products was attributable to the presence of colloidal silicon dioxide, used as a glidant in solid oral dosage forms [48]. This was ascribed to the fact that silicon dioxide can act as a Lewis acid (an election acceptor or oxidising agent), under anhydrous conditions. 

Glidants (e.g., colloidal silicon dioxide, talc) may need to be added to achieve desired flow properties, especially when the drug/filler ratio is relatively high. Usually, there is an optimum concentration of glidant for best flow, often less than 1% for the colloidal silicas (14,15). The following order of effectiveness of glidants has been reported for two powder systems fine silica > magnesium stearate > purified talc (16). 

Colloidal silicon dioxide Tablet glidant Polysorbate 80 Surfactant... 

Commonly used lubricants are listed in Table 5. Talc is traditionally one of the most commonly used glidants, having the additional benefit of being an excellent antiadherent. The level of talc that can be added to a formulation is restricted by its hydrophobic nature, too high levels resulting in decreased wetting of the tablet and a subsequent reduction in the rate of dissolution. Fumed silicon dioxides are... 

If a powder flows poorly, the vibrator can be used, but it also causes powder segregation and stratification. The addition of glidant (occasionally lubricant) in the powder mixtures can readily increase flowability at the low concerntration. Talc or fumed silicon dioxide is an example of a glidant. If this is not sufficient to improve the flow, other means of flow improvement are necessary. There are two main factors that affect powder flow particle size and particle shape. The more spherical a particle is, the better it flows. Small particles are very cohesive and hence do not flow well, but increasing the particle size will improve flow. With the aid of spray drying or spheronizers, particles become spherical. 

Colloidal Silcion dioxide is an agent that has been commonly used as a glidant. Flow rate, density, as well as other related measurements, were conducted on four different excipients. The addition of 1% colloidal silicon dioxide increased the flow of the poorer flowing excipients but had lesser affects on the exipients that were of larger size and were better flowing. Increasing amounts of chlorpromazine hydrochloride markedly decreased the flow characteristics of all the various blends. The particle size of the excipient blend... 

Silicon dioxide, colloidal 0.05-0.5 Excellent glidant (Aerosil , Cab-o-Sil )... 

It must be stressed that the functions of a glidant and lubricant in a tablet formulation are totally different. A few materials, e.g. talc, can act as both glidant and lubricant, but usually two different excipients are needed. Thus, although colloidal silicon dioxide is an excellent glidant, it has no lubricant activity. Conversely, magnesium stearate, despite its popularity as a lubricant, can hinder rather than promote flow. 

Comments finely ground crystalline fructose containing <2% silicon dioxide as a glidant. 

The fumed silicon dioxides are perhaps the most effective glidants. These are materials with very small (10 nm) spherical particles that may achieve their glidant properties by rolling over each other under shear stress. They are available in a number of grades with a range of hydrophobic and hydrophillic forms. 

S. Jonat, P. Albers, A. Gray, P.C. Schmidt, Investigation of the glidant properties of compacted colloidal silicon dioxide by angle of repose and X-ray photoelectron spectroscopy, European Journal of Pharmaceutics Biopharmaceutics, 63,356-359,2006. 

S. Jonat, S. Hasenzahl, A. Gray, P.C. Schmidt, Mechanism of glidants Investigation of the effect of different colloidal silicon dioxide types on powder flow by atomic force and scanning electron microscopy. Journal of Pharmaceutical Sciences, 93, 2635-2644,2004. 

S. Jonat, S. Hasenzahl, M. Drechsler, P. Albers, K.G. Wagner, P.C. Schmidt, Investigation of compacted hydrophilic and hydrophobic colloidal silicon dioxides as glidants for pharmaceutical excipients. Powder Technology, 141,31-43,2004. 

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