Magnesium stearate

• BPMagnesium Stearate
• JPMagnesium Stearate
• Ph. Eur.Magnesium Stearate
• USP–NFMagnesium Stearate

Dibasic magnesium stearate; magnesium distearate; magnesii stearas; magnesium octadecanoate; octadecanoic acid, magnesium salt; Synpro 90; E470b

Octadecanoic acid magnesium salt · [557-04-0]

UNII 70097M6I30 · PubChem CID 11177

C36H70MgO4 · 591.24

Lubricant

Typical concentrations: 0.25–5% · Dosage forms: Solid

Used mainly as a lubricant in tablet and capsule manufacture, at 0.25–5.0% w/w. It is also used in barrier creams and as a food additive.

A very fine, light, white, precipitated or milled powder of low bulk density, with a faint odour of stearic acid and a characteristic taste. It is greasy to the touch and adheres readily to the skin. The material is a mixture of magnesium salts of fatty acids, mainly stearic and palmitic acid; Ph. Eur. requires stearic acid ≥ 40% and stearic plus palmitic acid ≥ 90% of the fatty-acid fraction.

Crystalline forms

trihydrate (acicular), dihydrate (lamellar) and anhydrate; commercial material is often a mixture, and the form affects lubricant performance

Density

bulk ≈ 0.16 g/cm³; tapped ≈ 0.29 g/cm³; true ≈ 1.09 g/cm³

Melting range

117–150 °C (commercial material); 126–130 °C (high-purity material)

Specific surface area

1.6–14.8 m²/g, depending on grade

Solubility

practically insoluble in water, ethanol and ether; slightly soluble in warm benzene and warm ethanol (95%)

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

Incompatible with strong acids, alkalis and iron salts; avoid mixing with strong oxidising materials. It should not be used with aspirin, some vitamins and most alkaloidal salts.

Prepared either by reacting aqueous solutions of magnesium chloride and sodium stearate, or by reacting magnesium oxide, hydroxide or carbonate with stearic acid at elevated temperature.

Widely used in oral products and regarded as non-toxic after oral administration. Very large oral doses may have a laxative effect or irritate the mucosa. The fine powder should not be inhaled.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended, and a dust respirator where dust is generated; use with adequate ventilation.

GRAS listed. Accepted as a food additive in Europe (E470b). Included in the FDA Inactive Ingredient Database (oral capsules, powders and tablets; buccal and vaginal tablets; topical preparations) and in non-parenteral medicines licensed in Europe.

Calcium stearate; magnesium aluminium silicate; stearic acid; zinc stearate.

Magnesium stearate is hydrophobic and can slow the dissolution of a drug from a solid dosage form, so the lowest effective level should be used. Over-blending lowers tablet hardness and lengthens disintegration and dissolution; it is normally added last and blended for a short time (typically 2–5 minutes). Lubricant performance varies between suppliers and lots because of differences in hydrate form, particle size and specific surface area.