Food additives Europe numbers: E500
Functional Category
Alkalizing agent; buffering agent.
Applications in Pharmaceutical Formulation
Sodium carbonate is used as an alkalizing agent in injectable, ophthalmic, oral, and rectal formulations. In effervescent tablets or granules, sodium carbonate is used in combination with an acid, typically citric acid or tartaric acid.(1) When the tablets or granules come into contact with water, an acid– base reaction occurs in which carbon dioxide gas is produced and the product disintegrates.(2) Raw materials with low moisture contents are required to prevent the early triggering of the effervescent reaction.(2) As an alkalizing agent, concentrations of sodium carbonate between 2% and 5% w/w are used in compressed tablet formulations.(1,3) As an effervescent agent, concentrations of sodium carbonate up to 10% w/w can be used.(2) Therapeutically, sodium carbonate is also used as an oral antacid.(4)
Description
Sodium carbonate is a white, almost white, or colorless inorganic salt, produced as crystalline powder or granules. It is hygroscopic and odorless with an alkaline taste.
Stability and Storage Conditions
Sodium carbonate converts to the monohydrate form when in contact with water and produces heat. It begins to lose carbon dioxide at temperatures above 4008C(7) and decomposes before boiling. Store in airtight containers.
Incompatibilities
Sodium carbonate decomposes when in contact with acids in the presence of water to produce carbon dioxide and effervescence. It may react violently with aluminum, phosphorous pentoxide, sulfuric acid, fluorine, and lithium
Safety
Sodium carbonate is used in injectable, oral, and rectal pharmaceutical formulations. The pure form of sodium carbonate is mildly toxic by ingestion, moderately toxic by inhalation and SC routes, and very toxic by the IP route. It is irritating to the skin and eyes. Dust and vapors of sodium carbonate may irritate mucous membranes, causing coughing and shortness of breath. It also has experimental reproductive effects. Sodium carbonate can migrate to food from packaging materials. When used as an excipient or antacid, sodium carbonate is generally regarded as a nontoxic and nonirritating material. LD50 (mouse, IP): 0.12 g/kg(8) LD50 (mouse, SC): 2.21 g/kg LD50 (rat, oral): 4.09 g/kg