Magnesium Oxide

Category

Anticaking Agents; Emulsifying Agents; Glidant; Tablet and Capsule Diluent

Molecular Formula

MgO

Molecular Weight

40.3

Grade

Pharmceutical Excipients

Description

Two forms of magnesium oxide exist: a bulky form termed light magnesium oxide and a dense form termed heavy magnesium oxide. Both forms of magnesium oxide occur as fine, white, odorless powders.

UNII

3A3U0GI71G

Chemical Name

Magnesium oxide

CAS Number

1309-48-4

Synonyms

Calcined magnesia; calcinated magnesite; Descote; E530; Magcal; Magchem 100; Maglite; magnesia; magnesia monoxide; magnesiausta; magnesii oxidum leve; magnesii oxidum ponderosum; Magnyox; Marmag; Oxymag; periclase

Administration route

Oral and buccal

Dosage Form

Oral capsules, tablets, and buccal

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.

Source and Preparation

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.

Applications

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.

Safety

Magnesium oxide is widely used in oral formulations as an excipient and as a therapeutic agent. Therapeutically, 250-500 mg is administered orally as an antacid and 2-5 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.

Incompatibilities

Magnesium oxide is a basic compound and as such can react with acidic compounds in the solid state to form salts such as Mg(ibuprofen)2 or degrade alkaline-labile drugs.