Magnesium trisilicate

• BPMagnesium Trisilicate
• Ph. Eur.Magnesium Trisilicate
• USP–NFMagnesium Trisilicate

Magnesium mesotrisilicate; hydrated magnesium trisilicate; magnesii trisilicas; silicic acid, magnesium salt (1:2), hydrate

Magnesium trisilicate (hydrated) · [14987-04-3]

UNII FML8G1U0Y3 · PubChem CID 5311266

2MgO·3SiO2·xH2O · 260.86 (anhydrous)

Glidant, Adsorbent

Typical concentrations: — · Dosage forms: Solid

Used in oral pharmaceutical products and foods as a glidant and adsorbent. It is used more widely as an active ingredient, an antacid, often combined with aluminium hydroxide.

A white, odourless, tasteless, fine powder, free from grittiness.

Loss on ignition

17–34% w/w

Solubility

practically insoluble in water and ethanol; readily decomposed by mineral acids

Hygroscopicity

slightly hygroscopic

Acid-neutralising behaviour

neutralises acid slowly, forming gelatinous hydrated silica

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

Decomposed by acids. It adsorbs many drugs and can reduce the absorption of, for example, tetracyclines, nitrofurantoin and some antimuscarinics; it also binds preservatives such as parabens, reducing their efficacy.

Prepared by precipitation from solutions of sodium silicate and a soluble magnesium salt, such as magnesium sulfate, followed by washing and drying.

Regarded as non-toxic at excipient levels. Prolonged ingestion of large antacid doses has caused silica-containing kidney stones, and magnesium may accumulate in renal impairment. Large doses can be laxative.

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

Described in the Ph. Eur. and USP–NF and used in non-parenteral (oral) medicines licensed in Europe.

Magnesium silicate; magnesium aluminium silicate; aluminium hydroxide; talc.

Its strong adsorptive capacity is an advantage as a glidant but a risk for low-dose drugs and preserved liquids; check drug assay, preservative efficacy and dissolution when it is included in a formulation.