Magnesium stearate, also called octadecanoic acid, magnesium salt, is a
white substance, powder which becomes solid at room temperature. It has the
chemical formula Mg(C 18H
35O 2)
2. It is a salt containing two equivalents of stearate and one
magnesium cation. Magnesium stearate melts at about 88 °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 Substances
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." Manufacturing
Magnesium stearate is created by the reaction of sodium stearate with
magnesium sulfate. Uses
Magnesium stearate is often used as an anti-adherent in the manufacture of
medical tablets, capsules and powders. In this regard, the substance is also
useful, because it has lubricating properties, preventing ingredients from
sticking to manufacturing equipment during the compression of chemical
powders into solid tablets; magnesium stearate is the most commonly used
lubricant for tablets. Magnesium stearate can also be used efficiently in
dry coating processes. Studies have shown that magnesium stearate may affect
the release time of the active ingredients in tablets, etc., but not
that it reduces the overall bioavailability of those ingredients. As
a food additive or pharmaceutical excipient, its E number is E470b.
Magnesium stearate is also used to bind sugar in hard candies like mints, and is
a common ingredient in baby formulas. In pure powder form, the substance can be a
dust explosion hazard, although this issue is effectively insignificant
beyond the manufacturing plants using it.
Magnesium stearate is manufactured from both animal and vegetable oils. Some
nutritional supplements specify that the magnesium stearate used is sourced from
vegetables. Magnesium stearate is a major component
of "bathtub rings." When produced by soap and hard water, magnesium stearate
and calcium stearate both form a white solid insoluble in water, and are
collectively known as "soap scum." References
^ D. Søndergaarda, O. Meyera and G. Würtzena. "Magnesium stearate given
peroprally to rats. A short term study". Toxicology 17: 51–55.
doi:10.1016/0300-483X(80)90026-8. PMID 7434368.
^ FDA's SCOGS Database; Report No. 60; ID Code: 557-04-0; Year: 1979
^ Steve Ritter. "What's That Stuff? Excipients: Inactive ingredients in
medicines serve multiple functions in drug delivery". Chemical & Engineering
News 86: 25. doi:10.1021/cen-v086n001.p025.
^ Sworbrick, James; James C. Boylan. Encyclopedia of pharmaceutical
technology. p. 2274. ISBN 9780824728243. ^ Weiner, Myra L.; Lois A. Kotkoskie.
Excipient Toxicity and Safety. p. 10. ISBN 9780824782108.
^ Ouabbas Y, Dodds J., Galet L., Chamayou A. , Baron M.,
Particle-particle coating in a cyclomix impact mixer, Powder Technol., 189,
245-252 ^ Thomas G., Ouabbas Y., Grosseau P.,
Baron M., Chamayou A., Galet L., Modeling the main interaction forces
between powder particles. Application to silica gel-magnesium stearate mixtures,
Applied Surface Science, 255, 7500-7507 ^ Sato A., Serris E., Grosseau P.,
Thomas G., Galet L., Chamayou A. , Baron M., Experiment and simulation of dry
particle coating, Chem. Eng. Science, 86, 164-172
^ Alija Uzunović, Edina Vranić; "Effect Of Magnesium Stearate Concentration On
Dissolution Properties Of Ranitidine Hydrochloride Coated Tablets"; Bosnian
Journal Of Basic Medical Sciences, 2007, 7(3): 279-283
^ Natalie D. Eddington, Muhammad Ashraf, Larry L. Augsburger, James L. Leslie,
Michael J. Fossler, Lawrence J. Lesko, Vinod P. Shah, Gurvinder Singh Rekhi;
"Identification of Formulation and Manufacturing Variables That Influence
In Vitro Dissolution and In Vivo Bioavailability of Propranolol
Hydrochloride Tablets"; Pharmaceutical Development and Technology, Volume 3,
Issue 4 November 1998 , pages 535–547 ^ International Chemical Safety Card
1403 ^ Anne Marie Helmenstine; About.com:
"Why Is It Harder to Rinse off Soap with Soft Water?"; retrieved 19 Mar 2010