title: Tableting properties of silica aerogel and other silicates.
abstract: BACKGROUND
  In solid oral dosage forms silicates are commonly used as glidants in low concentration. However, due to their large specific surface area, silicates may also be used as carrier materials for drugs. Moreover, silicates allow amorphisation of drugs by co-grinding or processing with supercritical fluids.
  
  
  OBJECTIVE
  The aim of this study was to investigate the physical and the tableting properties of Silica Aerogel (special type of silica with an extremely large specific surface area), Neusilin(®) US2 (magnesium aluminometasilicate), Florite(®) (calcium silicate) and Aerosil(®) 200 (colloidal silica).
  
  
  METHODS
  Powder blends of Avicel(®) PH102 (microcrystalline cellulose) and different amounts of the respective silicate were compacted and analyzed for their tabletability (tensile strength vs. compaction pressure) as well as their Heckel plot.
  
  
  CONCLUSIONS
  With Neusilin(®) the tabletability appeared to be independent of the silicate concentration, whereas with Florite(®) an increasing silicate concentration led to a higher tensile strength. In contrast, the addition of Silica Aerogel and Aerosil(®) resulted in a decrease of the tensile strength. With Aerosil(®) a maximum tolerable concentration of 20% [w/w] was determined. Plastic deformation of all powder blends decreased with increasing silicate concentration. This effect was most pronounced with Aerosil(®) and least with Florite(®).
  
  
  CONCLUSIONS
  Tablets with acceptable tensile strength were obtained with all plain silicates except for Aerosil(®). Therefore, these silicates may be used in tablet formulations, e.g. as carrier materials for liquid or amorphous drugs.
authors.affiliation: Institute of Pharmacy, Department of Pharmaceutical Technology, University of Hamburg, Hamburg, Germany.
authors.forename: C M
authors.initials: CM
authors.lastname: Hentzschel
authors.forename: M
authors.initials: M
authors.lastname: Alnaief
authors.forename: I
authors.initials: I
authors.lastname: Smirnova
authors.forename: A
authors.initials: A
authors.lastname: Sakmann
authors.forename: C S
authors.initials: CS
authors.lastname: Leopold
mesh_terms: D017607:Aluminum Compounds; D000538:Aluminum Silicates / Q000737:chemistry; D002482:Cellulose / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry; D017616:Magnesium Compounds; D058428:Silica Gel / Q000737:chemistry; D017640:Silicates / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D013607:Tablets / Q000737:chemistry*; D013718:Tensile Strength
chemical_list: D017607:Aluminum Compounds; D000538:Aluminum Silicates; D004337:Drug Carriers; D017616:Magnesium Compounds; D017640:Silicates; D013607:Tablets; D058428:Silica Gel; C033065:aluminum magnesium silicate; D012822:Silicon Dioxide; D002482:Cellulose; D008274:Magnesium