Nonproprietary Names

None adopted.

Synonyms

Activated alumina; activated aluminum oxide; alpha aluminum oxide; alumina; alumina, calcined; alumina, tabular; aluminum oxide alumite; aluminum trioxide; gamma aluminum oxide.

Chemical Name and CAS Registry Number

Aluminum oxide [1344-28-1]

Empirical Formula and Molecular Weight

Al2O3 101.96

Structural Formula

Aluminum oxide occurs naturally as the minerals bauxite, bayerite, boehmite, corundum, diaspore, and gibbsite.

Functional Category

Adsorbent; dispersing agent.

Applications in Pharmaceutical Formulation or Technology

Technology Aluminum oxide is used mainly in tablet formulations.(1) It is used for decoloring powders and is particularly widely used in antibiotic formulations. It is also used in suppositories, pessaries, and urethral inserts. Hydrated aluminum oxide (see Section 18) is used in mordant dyeing to make lake pigments, in cosmetics, and therapeutically as an antacid.

Description

Aluminum oxide occurs as a white crystalline powder. Aluminum oxide occurs as two crystalline forms: a-aluminum oxide is composed of colorless hexagonal crystals, and g-aluminum oxide is composed of minute colorless cubic crystals that are transformed to the a-form at high temperatures.

Pharmacopeial Specifications

See Section 18.

Typical Properties

Boiling point 29778C Density (bulk) 0.91.1g/cm3 Flammability Nonflammable. Hardness (Mohs) 8.8 Hygroscopicity Very hygroscopic. Melting point 20508C Solubility Slowly soluble in aqueous alkaline solutions with the formation of hydroxides; practically insoluble in nonpolar organic solvents, diethyl ether, ethanol (95%), and water. Specific gravity 2.8 (becomes 4.0 at 8008C) Vapor pressure 133.3Pa at 21588C

Stability and Storage Conditions

Aluminum oxide should be stored in a well-closed container in a cool, dry, place. It is very hygroscopic.

Incompatibilities

Aluminum oxide should be kept well away from water. It is incompatible with strong oxidizers and chlorinated rubber. Aluminum oxide also reacts with chlorine trifluoride, ethylene oxide, sodium nitrate, and vinyl acetate. Exothermic reactions above 2008C with halocarbon vapors produce toxic hydrogen chloride and phosgene fumes.

Method of Manufacture

Most of the aluminum oxide produced commercially is obtained by the calcination of aluminum hydroxide.

Safety

Aluminum oxide is generally regarded as relatively nontoxic and nonirritant when used as an excipient. Inhalation of finely divided particles may cause lung damage (Shaver’s disease).(2)

Handling Precautions

Observe normal precautions appropriate to the circumstances and quantity of the material handled.(3) In the UK, the workplace exposure limits for aluminum oxide are 10mg/m3 long-term (8hour TWA) for total inhalable dust and 4mg/m3 for respirable dust.(4) In the USA, the OSHA limit is 15mg/m3 total dust, 5mg/m3 respirable fraction for aluminium oxide.(5)

Regulatory Status

Included in the FDA Inactive Ingredients Database (oral tablets and topical sponge). Included in nonparenteral medicines licensed in the UK. 17 Related Substances —

Comments

A specification for aluminum oxide is included in the Japanese Pharmaceutical Excipients (JPE);(6) see Table I. A specification for Aluminum Phosphate Adjuvant light aluminum oxide is also included. The PhEur 6.3 includes a specification for hydrated aluminum oxide that contains the equivalent of 47.0–60.0% of Al2O3. The EINECS number for aluminum oxide is 215-691-6. Table I: JPE specification for aluminum oxide.(6) Test JPE 2004 Identification Water-soluble substances þ þ Heavy metals 430 ppm Lead 430 ppm Arsenic 45 ppm Loss on drying 41.5% Loss on ignition 42.5% Assay 596.0% 19 Specific References 1 Rupprecht H. Processing of potent substances with inorganic supports by imbedding and coating. Acta Pharm Technol 1980; 26: 13–27. 2 Lewis RJ, ed. Sax’s dangerous Properties of Industrial Materials, 11th edn. New York: Wiley, 2004; 136. 3 National Poisons Information Service 1997. Aluminium oxide. http:// www.intox.org/databank/documents/chemical/alumoxde/ukpid33.htm (accessed 16 January 2009) 4 Health and Safety Executive. EH40/2005: Workplace Exposure Limits. Sudbury: HSE Books, 2005 (updated 2007). http://www.hse.gov.uk/ coshh/table1.pdf (accessed 5 February 2009). 5 JT Baker (2007). Material safety data sheet: Aluminium oxide. http:// www.jtbaker.com/msds/englishhtml/a2844.htm (accessed 5 February 2009). 6 Japan Pharmaceutical Excipients Council. Japanese Pharmaceutical Excipients 2004. Tokyo: Yakuji Nippo, 2004; 67–68.

General References

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Author

T Farrell.

Date of Revision

5 February 2009.