Tableting properties of silica aerogel and other silicates

Abstract

Context: 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). Materials and 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. Results and discussion: 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^®. Conclusion: 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.

Keywords::

• Silica aerogel
• silicate
• Neusilin®
• Florite®
• Aerosil®
• tabletability

Acknowledgements

The authors would like to thank Dr. Markus Thommes (Institute of Pharmacy, Department of Pharmaceutical Technology, University of Duesseldorf) for determination of the moisture sorption isotherms. Furthermore, the authors would like to thank FMC BioPolymer, SEPPIC, Tokuyama, and Evonik for the donation of the excipients.

Declaration of interest

The authors report no declarations of interest.