Description
Magnesium stearate, also called octa decanoic acid, magnesium salt, is a white substance, powder which becomes solid at room temperature. It has the chemical formula Mg(C18H35O2)2. It is a salt containing two equivalents of stearate (the anion of stearic acid) and one magnesium cation (Mg2+). Magnesium stearate melts at about 120 °C, is not soluble in water, and is generally considered safe for human consumption at levels below 2500 mg/kg per day.In 1979, the FDA's Subcommittee on GRAS (generally recognized as safe) Substances (SCOGS) reported, "There is no evidence in the available information on ... magnesium stearate ... that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current and in the manner now practiced, or which might reasonably be expected in the future.".
Preparation
Magnesium stearate is created by the reaction of sodium stearate with magnesium sulfate.
Production Methods
Magnesium stearate is prepared either by the interaction of aqueous
solutions of magnesium chloride with sodium stearate or by the
interaction of magnesium oxide, hydroxide, or carbonate with
stearic acid at elevated temperatures.
General Description
Magnesium stearate (Mg-St) is the magnesium salt of stearic acid. Its anhydrate, dihydrate and trihydrate forms have been prepared. The tabletting of the blends of magnesium stearate and lactose granules has been described. The influence of mixing time on hardness, disintegration time and ejection force on the compressed tablets was examined. Mg-St is widely used lubricant in pharmaceutical industry. It also plays a role in delaying the process of dissolution. Its detection in tablets by laser-induced breakdown spectroscopy has been proposed.
Biochem/physiol Actions
Magnesium stearate is the magnesium salt of stearic acid that possess lubricating properties and hence prevents ingredients from sticking to manufacturing equipment during the compression of chemical powders into solid tablets. Dry coating of drugs with magnesium stearate leads to flow improvement, flow-aid and lubrication effects, tabletability as well as non-inhibited dissolution rate.
Safety
Magnesium stearate is widely used as a pharmaceutical excipient
and is generally regarded as being nontoxic following oral
administration. However, oral consumption of large quantities
may produce a laxative effect or mucosal irritation.
No toxicity information is available relating to normal routes of
occupational exposure. Limits for heavy metals in magnesium
stearate have been evaluated in terms of magnesium stearate worstcase
daily intake and heavy metal composition.
Toxicity assessments of magnesium stearate in rats have
indicated that it is not irritating to the skin, and is nontoxic when
administered orally or inhaled.
Magnesium stearate has not been shown to be carcinogenic
when implanted into the bladder of mice.
LD50 (rat, inhalation): >2 mg/L
LD50 (rat, oral): >10 g/kg
storage
Magnesium stearate is stable and should be stored in a well-closed
container in a cool, dry place.
Incompatibilities
Incompatible with strong acids, alkalis, and iron salts. Avoid mixing
with strong oxidizing materials. Magnesium stearate cannot be used
in products containing aspirin, some vitamins, and most alkaloidal
salts.
Regulatory Status
GRAS listed. Accepted as a food additive in the USA and UK.
Included in the FDA Inactive Ingredients Database (oral capsules,
powders, and tablets; buccal and vaginal tablets; topical preparapreparations;
intravitreal implants and injections). Included in nonparenteral
medicines licensed in the UK. Included in the Canadian List
of Acceptable Non-medicinal Ingredients. Listed on the US TSCA
inventory.
