Magnesium Oxide
Magnesium Oxide is known as an anti-caking agent, emulsifier, glidant (lubricant) and diluent for tablets and capsules. This material is present in Arvin Kala’s product portfolio.
Description
Two forms of magnesium oxide exist: a bulky form termed light magnesium oxide and a dense form termed heavy magnesium oxide. The USP 32 and JP XV define both forms in a single monograph, while the BP 2009 and PhEur 6.4 have separate monographs for each form. For the heavy variety, 15 g has an apparent volume before settling of not more than 60 mL; for the light variety, 15 g has an apparent volume before settling of not more than 100 mL as defined by the BP 2009 and PhEur 6.4.
Both forms of magnesium oxide occur as fine, white, odorless powders. Magnesium oxide possesses a cubic crystal structure, though the BP 2009 and PhEur 6.4 describe the appearance of light magnesium oxide as an amorphous powder.
Applications in Pharmaceutical Formulation or Technology
Magnesium oxide is used as an alkaline diluent in solid-dosage forms to modify the pH of tablets. It can be added to solid-dosage forms to bind excess water and keep the granulation dry. In combination with silica, magnesium oxide can be used as an auxiliary glidant. It is also used as a food additive and as an antacid, either alone or in conjunction with aluminum hydroxide. Magnesium oxide is additionally used as an osmotic laxative and a magnesium supplement to treat deficiency states.
Stability and Storage Conditions
Magnesium oxide is stable at normal temperatures and pressures. However, it forms magnesium hydroxide in the presence of water. Magnesium oxide is hygroscopic and rapidly absorbs water and carbon dioxide on exposure to the air, the light form more readily than the heavy form.
The bulk material should be stored in an airtight container in a cool, dry place.
Method of Manufacture
Magnesium oxide occurs naturally as the mineral periclase. It can be manufactured by many processes. Limestone containing the mineral dolomite is calcinated at high temperatures to produce dolime, which then reacts with magnesium chloride-rich sea water to produce magnesium hydroxide and calcium chloride.
The magnesium hydroxide is then calcinated to produce magnesium oxide and water. In another process, mined magnesite (MgCO3) is calcinated to produce magnesium oxide and carbon dioxide.
Purification methods include crushing and size separation, heavy media separation, and froth flotation. Producing magnesium oxide from sea water is a process that involves heating magnesium chloride concentrated brine from the Dead Sea. The magnesium chloride decomposes into magnesium oxide and hydrochloric acid. Magnesium oxide may also be produced by the thermal decomposition of magnesium chloride, magnesium sulfate, magnesium sulfite, nesquehonite, and the basic carbonate 5MgO.4CO2.5H2O. Purification of the magnesium oxide produced through thermal degradation is carried out by filtration or sedimentation.
Safety
Magnesium oxide is widely used in oral formulations as an excipient and as a therapeutic agent. Therapeutically, 250 to 500 mg is administered orally as an antacid and 2 to 5 g as an osmotic laxative. Magnesium oxide is generally regarded as a nontoxic material when employed as an excipient, although adverse effects, due to its laxative action, may occur if high doses are ingested orally
Handling Precautions
Observe normal precautions appropriate to the circumstances and quantity of material handled. Magnesium oxide may be harmful if inhaled, ingested, or absorbed through the skin in quantity, and is irritating to the eyes and respiratory system. Gloves, eye protection, and a dust mask or respirator are recommended. In the USA and UK, the long-term (8-hour TWA) workplace exposure limits for magnesium oxide, calculated as magnesium, are 10 mg/m3 for total dust and 4 mg/m3 for respirable dust. The short-term (15- minute) limit for respirable dust is 10 mg/m3 .
Chemical-physical values
| Item | Unit | Specification |
|---|---|---|
|
Appearance |
|
White to off white Powder |
|
Magnesium Oxide as MgO |
% |
Min 98.0 &
Max 100.5
|
|
ldentification |
|
Positive for Magnesium |
|
Free Alkali (as 0.1N H2SO4) |
ml |
Max 2.0 |
|
Soluble Salts |
% |
Max 2.00 |
|
Acid-lnsoluble Substances |
% |
Max 0.100 |
|
Chlorides as Cl |
ppm |
Max 1000 |
| Item | Unit | Specification |
|---|---|---|
|
Sulphates as SO4 |
% |
Max 1.00 |
|
Arsenic as As |
ppm |
Max 1.0 |
|
Calcium as Ca |
% |
Max 1.10 |
|
lron as Fe |
ppm |
Max 500 |
|
Loss on lgnition |
% |
Max 5.0 |
|
Lead as Pb |
ppm |
Max 0.2 |
|
Bulk Density |
gr/cc |
Min 0.25 |
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