Name: Magnesium Aluminum Silicate
CAS No: Aluminum magnesium silicate [12511-31-8], Magnesium aluminum silicate [1327-43-1]
BP: Aluminium Magnesium Silicate PhEur: Aluminium Magnesium Silicate USP-NF: Magnesium Aluminum Silicate
Aluminii magnesii silicas; aluminosilicic acid, magnesium salt; aluminum magnesium silicate; Carrisorb; Gelsorb; Magnabrite; magnesium aluminosilicate; magnesium aluminum silicate, colloidal; magnesium aluminum silicate, complex colloidal; Neusilin; Pharmasorb; silicic acid, aluminum magnesium salt; Veegum.
Aluminum magnesium silicate [12511-31-8], Magnesium aluminum silicate [1327-43-1]
Magnesium aluminum silicate is a polymeric complex of magnesium, aluminum, silicon, oxygen, and water. The average chemical analysis is conventionally expressed as oxides: Silicon dioxide 61.1% Magnesium oxide 13.7% Aluminum oxide 9.3% Titanium dioxide 0.1% Ferric oxide 0.9% Calcium oxide 2.7% Sodium oxide 2.9% Potassium oxide 0.3% Carbon dioxide 1.8% Water of combination 7.2%
The complex is composed of a three-lattice layer of octahedral alumina and two tetrahedral silica sheets. The aluminum is substituted to varying degrees by magnesium (with sodium or potassium for balance of electrical charge). Additional elements present in small amounts include iron, lithium, titanium, calcium, and carbon.
Magnesium aluminum 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.(1–3) 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.(4,5) See Table I. Magnesium aluminum silicate may cause bioavailability problems with certain drugs
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; see Table II. 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 0.4 mm to 1.0 2.0 mm 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.
See Table III.
Acid demand 6–8 mL of 0.1 N HCl is required to reduce the pH of 1 g to pH 4.
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.(7,8) This can result in low bioavailability if the drug is tightly bound or slowly desorbed, e.g. amfetamine sulfate,(4) tolbutamide,(9) warfarin sodium,(10) diazepam,(11) and diclofenac sodium.(12
Magnesium aluminum 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.
Magnesium aluminum 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.(13) LD50 (rat, oral): > 16 g/kg(14
Observe normal precautions appropriate to the circumstances and quantity of material handled. Eye protection and gloves are recommended. Adequate ventilation should be provided and dust generation minimized.
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
Attapulgite; bentonite; kaolin; magnesium silicate; magnesium trisilicate; montmorillonite; saponite; talc. Montmorillonite Empirical formula Al2O54SiO24H2O CAS number [1318-93-0] Comments A naturally occurring silicate clay.
The EINECS number for magnesium aluminum silicate is 215-478- 8. The PubChem Compound ID (CID) for magnesium aluminum silicate is 3084116.