Aluminum magnesium silicate is a white powder, granules or plates. It can be used as an excipient, such as adsorbent, stabilizer, suspending agent, disintegrant for tablet and capsule, binder for tablet, thickener. Incorporation of MAS into the diclofenac sodium (DS) aqueous gels caused a statistical increase in viscosity and a shift from Newtonian flow to pseudoplastic flow with thixotropic property.
Almost white powder, granules or plates.
The USP32–NF27 describes magnesium aluminum silicate as a
blend of colloidal montmorillonite and saponite that has been
processed to remove grit and nonswellable ore components. Four
types of magnesium aluminum silicate are defined: types IA, IB, IC,
and IIA. These types differ according to their viscosity and ratio of
aluminum and magnesium content.
The PhEur 6.3 describes magnesium aluminum silicate (aluminium
magnesium silicate) as a mixture of particles with colloidal particle size of montmorillonite and saponite, free from grit and
nonswellable ore.
Magnesium aluminum silicate occurs as off-white to creamy
white, odorless, tasteless, soft, slippery small flakes, or as a fine,
micronized powder. Flakes vary in shape and size from about 0.3
0.4mm to 1.0×2.0mm and about 25–240 mm thick. Many flakes
are perforated by scattered circular holes 20–120 mm in diameter.
Under dark-field polarized light, innumerable bright specks are
observed scattered over the flakes. The powder varies from 45 to
297 mm in size.
Aluminium magnesium silicate is used as an Antacid Raw material in a specific antacid formulations, Ceramics, Suspending Agent, Thickning agent etc.
Aluminium magnesium silicate is obtained from silicate ores of the
montmorillonite group, which show high magnesium content. The
ore is blended with water to form a slurry to remove impurities and
separate out the colloidal fraction. The refined colloidal dispersion
is drum-dried to form a small flake, which is then micro-atomized to
form various powder grades.
Pharmaceutical Applications
Aluminium magnesium silicate has been used for many years in the
formulation of tablets, ointments, and creams. It is used in oral and
topical formulations as a suspending and stabilizing agent either
alone or in combination with other suspending agents. The
viscosity of aqueous dispersions may be greatly increased by
combination with other suspending agents, such as xanthan gum,
owing to synergistic effects; see Xanthan Gum. In tablets,
magnesium aluminum silicate is used as a binder and disintegrant
in conventional or slow-release formulations.
Magnesium aluminum silicate may cause bioavailability problems
with certain drugs.
Aluminium magnesium silicate is generally regarded as nontoxic and
nonirritating at the levels employed as a pharmaceutical excipient.
Subacute animal feeding studies in rats and dogs fed magnesium
aluminum silicate at 10% of the diet, for 90 days, were negative,
including autopsy and histopathological examinations.
LD50 (rat, oral): > 16 g/kg
Magnesium aluminum silicate is stable indefinitely when stored
under dry conditions. It is stable over a wide pH range, has baseexchange
capacity, absorbs some organic substances, and is
compatible with organic solvents.
Magnesium aluminum silicate should be stored in a well-closed
container, in a cool, dry place.
Owing to its inert nature, magnesium aluminum silicate has few
incompatibilities but is generally unsuitable for acidic solutions
below pH 3.5. Magnesium aluminum silicate, as with other clays,may adsorb some drugs. This can result in low bioavailability if
the drug is tightly bound or slowly desorbed, e.g. amfetamine
sulfate, tolbutamide, warfarin sodium, diazepam, and
diclofenac sodium.
Included in the FDA Inactive Ingredients Database (oral granules,
solutions, suspensions and tablets; rectal; and topical preparations;
vaginal preparations). Included in nonparenteral medicines licensed
in the UK. Included in the Canadian List of Acceptable Nonmedicinal
Ingredients.
