Colloidal silicon dioxide, glidant

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... 

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... 

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. 

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. 

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

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