Magnesium silicate

• JPMagnesium Silicate
• USP–NFMagnesium Silicate

Synthetic magnesium silicate; hydrated magnesium silicate; magnesium silicate hydrate; E553a

Magnesium silicate (variable composition) · [1343-88-0]

MgO·xSiO2·yH2O (variable)

Glidant

Typical concentrations: — · Dosage forms: Solid

Used in oral pharmaceutical products and foods as a glidant and anticaking agent, and as an adsorbent. Therapeutically it has been used as an antacid. It has also been used as a filter aid and in chromatography.

A fine, white, odourless and tasteless powder, free from grittiness. It is a synthetic compound of magnesium oxide and silicon dioxide with varying amounts of water.

pH

7.0–10.8 (10% w/v aqueous slurry)

Solubility

practically insoluble in water and ethanol; decomposed by mineral acids

Hygroscopicity

slightly hygroscopic

Surface

porous, with a high specific surface area and good adsorptive capacity

Stable. Store in a well-closed container in a cool, dry place.

Decomposed by acids. Because of its adsorptive capacity it may bind drugs and preservatives, and magnesium ions may chelate drugs such as tetracyclines, so drug release and availability should be checked.

Made by precipitation from an aqueous solution of sodium silicate with a soluble magnesium salt, followed by washing, drying and milling.

Regarded as non-toxic and non-irritant at excipient levels. Long-term ingestion of large amounts of magnesium silicates (as antacids) has been associated with silica kidney stones. Inhalation of the dust should be avoided.

Observe normal precautions for the quantity handled. Avoid generating dust; eye protection, gloves and a dust mask are recommended.

GRAS listed as an anticaking agent. Accepted as a food additive in Europe (E553a).

Magnesium trisilicate; magnesium aluminium silicate; calcium silicate; talc.

Composition (the MgO to SiO2 ratio and water content) varies between products, which affects adsorption and flow properties; the supplier's specification should be checked against the intended use.