Monograph: |
Magnesium Trisilicate
A hydrated magnesium silicate corresponding approximately
to the formula 2Mg0.3Si02. with water of crystallisation. An
odourless, white powder free from gritty particles. Practically
insoluble in water and alcohol. It is readily decomposed by
mineral acids.
Magnesium trisilicate is an antacid with general properties
similar to those of magnesium hydroxide .It is given
in doses of up to about 2 g by mouth. When given by mouth
it reacts slowly with hydrochloric acid in the gastric secretion
to form magnesium chloride and silicon dioxide and is prima-
rily excreted in the faeces as insoluble and soluble magnesi-
um salts. The antacid action is therefore exerted slowly, so
that it does not give such rapid symptomatic relief as magne-
sium carbonate or magnesium hydroxide: passage through
the stomach may be too rapid for it to exert a significant acid-
neutralising effect. Magnesium trisilicate is often given in
conjunction with aluminium-containing antacids such as alu-
minium hydroxide which counteract its laxative effect.
Magnesium trisilicate is also used as a food additive.
Effects on the kidneys. A 68-year-old man with a history
of renal calculus passed a 300-mg stone which was found to
consist chiefly of silica. He had been taking the equivalent of
2 g of magnesium trisilicate daily for many years.
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