Chemical Properties
White to slightly yellowish fine cryst. powder
Uses
As antifermentative in breweries and wineries; bleaching straw; preservative for fruits and vegetables.
General Description
Potassium disulfite (Potassium metabisulfite, PMB) is an inorganic salt with antimicrobial properties. It is a sulfiting agent that prevents browning of foods.
Pharmaceutical Applications
Potassium metabisulfite is used in applications similar to those of
sodium metabisulfite in pharmaceuticals, and in the food, brewing,
and wine making industries. It is used as an antioxidant,
antimicrobial preservative and sterilizing agent.
Safety
Potassium metabisulfite is used in a variety of foods and
pharmaceutical preparations, including oral, otic, rectal, and
parenteral preparations. Potassium metabisulfite is considered a
very irritating material, and may cause dermatitis on exposed
skin.
Hypersensitivity reactions to potassium metabisulfite and other
sulfites, mainly used as preservatives in food products, have been
reported. Reactions include bronchospasm and anaphylaxis; some
deaths have also been reported, especially in those with a history of
asthma or atopic allergy.These reactions have led to
restrictions by the FDA on the use of sulfites in food applications.
However, this restriction has not been extended to their use in
pharmaceutical applications. Indeed, epinephrine (adrenaline)
injections used to treat severe allergic reactions may contain
sulfites.
The WHO has set an acceptable daily intake of sulfites, as SO2,
at up to 0.35 mg/kg body-weight.
storage
Potassium metabisulfite should be stored in a cool, dark place.
When stored at a maximum temperature of 25°C and maximum
relative humidity of 45%, the shelf-life is 6 months. Potassium
metabisulfite decomposes at temperatures above 150°C. In the air, it
oxidizes to the sulfate, more readily in the presence of moisture.
In aqueous solution, potassium metabisulfite forms potassium
bisulfite (KHSO3) which exerts a strong reducing effect.
Incompatibilities
Potassium metabisulfite is incompatible with strong acids, water,
and most common metals. It reacts with nitrites and sodium nitrate
at room temperature, which occasionally results in the formation of
flame. The reaction may be explosive if water is present. Potassium
metabisulfite liberates SO2 with acids.
Sulfites, including potassium metabisulfite, can react with
various pharmaceutical compounds including sympathomimetics
such as epinephrine (adrenaline),chloramphenicol,cisplatin,
and amino acids,which can result in their pharmacological
inactivation. Sulfites are also reported to react with phenylmercuric
nitrate,and may adsorb onto rubber closures.
Regulatory Status
GRAS listed. Accepted in Europe for use as a food additive in
certain applications. Included in the FDA Inactive Ingredients
Database (IM and IV injection; otic and rectal solutions and
suspensions). Included in the Canadian List of Acceptable Nonmedicinal
Ingredients.
