Name: Magnesium Oxide
CAS No: Magnesium oxide [1309-48-4]
BP: Heavy Magnesium Oxide Light Magnesium Oxide JP: Magnesium Oxide PhEur: Magnesium Oxide, Heavy Magnesium Oxide, Light USP: Magnesium Oxide
Calcined magnesia; calcinated magnesite; Descote; E530; Magcal; Magchem 100; Maglite; magnesia; magnesia monoxide; magnesia usta; magnesii oxidum leve; magnesii oxidum ponderosum; Magnyox; Marmag; Oxymag; periclase.
Magnesium oxide [1309-48-4]
MgO 40.30
See Section 4.
Magnesium oxide is used as an alkaline diluent in solid-dosage forms to modify the pH of tablets.(1) 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.(2) 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.
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
See Table I.
Acidity/alkalinity pH = 10.3 (saturated aqueous solution) Boiling point 36008C Melting point 28008C NIR spectra see Figure 1. Particle size distribution 99.98% less than 45 mm in size (light magnesium oxide). Refractive index 1.735 Solubility Soluble in dilute acids and ammonium salt solutions; very slightly soluble in pure water (0.0086 g/100 mL at 308C; solubility is increased by carbon dioxide); practically insoluble in ethanol (95%). Specific gravity 3.58 g/cm3 at 258C (heavy magnesium oxide).
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.
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.(3) Adsorption of various drugs onto magnesium oxide has been reported, such as antihistamines,(4) antibiotics (especially tetracyclines),(5) salicylates,(6) atropine sulfate,(7) hyoscyamine hydrobromide,(7) paracetamol, chloroquine;(8) and anthranilic acid derivatives have been reported to adsorb onto the surface of magnesium oxide.(9) Magnesium oxide can also complex with polymers, e.g. Eudragit RS, to retard drug release(10–12) and can interact in the solid state with phenobarbitone sodium.(13) Magnesium oxide can also reduce the bioavailability of phenytoin,(14) trichlormethiazide,(15) and antiarrhythmics.(16) The presence of magnesium oxide can also have a negative impact on the solid-state chemical stability of drugs, such as diazepam.(17) Magnesium oxide has been used as a stabilizer for omeprazole due to its strong waterproofing effect.(18)
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.(19) 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.(19) 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.(19) Magnesium oxide may also be produced by the thermal decomposition of magnesium chloride, magnesium sulfate, magnesium sulfite, nesquehonite, and the basic carbonate 5MgO4CO25H2O. Purification of the magnesium oxide produced through thermal degradation is carried out by filtration or sedimentation.
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
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.(19,20) The short-term (15- minute) limit for respirable dust is 10 mg/m3 . (19
GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral capsules, tablets, and buccal). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
A specification for magnesium oxide is contained in the Food Chemicals Codex (FCC).(21) The EINECS number for magnesium oxide is 215-171-9. The PubChem Compound ID (CID) for magnesium oxide is 14792.