Attapulgite

Activated attapulgite; colloidal activated attapulgite; Attagel; palygorskite; Pharmasorb

Hydrated magnesium aluminium silicate clay (palygorskite) · [12174-11-7]

approximately (Mg,Al)5Si8O20(OH)2(OH2)4·4H2O

Adsorbent

Typical concentrations: — · Dosage forms: Solid, Liquid

Used as a suspending, thickening and thixotropic agent in oral and topical suspensions and as an adsorbent. Heat-activated attapulgite was formerly widely used as an antidiarrhoeal active ingredient. Colloidal grades are used as rheology modifiers in pharmaceutical, cosmetic and industrial products.

A cream to buff-coloured, very fine, odourless powder with a slightly earthy taste. It is a naturally occurring clay mineral (palygorskite) with a chain-type structure that forms elongated, needle-shaped particles.

Particle shape

acicular (needle-like) crystals that form a lattice-like network in water

Solubility

practically insoluble in water and organic solvents; disperses in water without the marked swelling seen with bentonite

Adsorptive capacity

high, and increased by thermal activation

Electrolyte tolerance

dispersions retain viscosity in the presence of electrolytes better than swelling smectite clays

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

Because of its high adsorptive capacity it can bind drugs, preservatives and flavours given at the same time, reducing their availability or activity.

Mined from natural deposits, then dried, milled and classified. Activated grades are produced by controlled heating, which removes water and increases adsorptive capacity; colloidal grades are processed to a very fine particle size.

Not absorbed from the gastrointestinal tract and regarded as of low toxicity orally. Long-term inhalation of clay dusts, which may contain crystalline silica, should be avoided.

Observe normal precautions for the quantity handled. Avoid dust generation and use a suitable dust mask and eye protection.

In the USA, attapulgite was removed from the over-the-counter antidiarrhoeal monograph in 2003 because of insufficient evidence of effectiveness, but it remains in use as an excipient and in some markets as an active ingredient.

Bentonite; kaolin; magnesium aluminium silicate; sepiolite.

Unlike swelling clays such as bentonite, attapulgite builds viscosity through a network of interlocking needles rather than through swelling, so its suspensions are less sensitive to electrolytes. Its adsorptive capacity should be considered whenever it is co-formulated with low-dose drugs.