Monograph: |
Alginic Acid
A mixture of polyuronic acids composed of residues of D - mannurronic and l - guluronic acids exracted from algae belonging to the Phaeophyceae. A white to pale yellowish - brown, odourless or almost odourless, crystalline, fibrous, or amorphous powder.
It swells in water but does not dissolve. Very slightly soluble or practically insoluble in alcohol ; practically insoluble in organic solvents ; dissolves in solutions of alkali hydroxides. A 3% dispersion in water has a pH of 1.5 to 3.5.
Uses and Administration
Alginic acid and alginates such as propylene glycol alginate and sodium alginate are used in pharmaceutical manufacturing as suspending and thickening agents. They may be used as stabilisers for oil --in - water emulsions and as binding and disintegrating agents in tablets. Various grades are usually available commercially for different applications and yield solutions of varying viscosity. A reduction in viscosity has been said to occur following sterilisation by autoclaving of sodium alginate solutions.
Alginic acid and alginates (ammonium alginate, calcium alginate, potassium alginate, propylene glycol alginate, and sodium alginate) are also employed as emulsifiers and stabilisers in the food industry.
Alginic acid or the alginates, magnesium alginate and sodium alginate, are used with antacid or histamine H2 - receptor antagonist such as cimetidine in the management of gastro - oesophageal reflux disease. Alginic acid or the alginate reacts with gastric acid to form a viscous gel (often termed a raft) which floats on top of the gastric contents. This raft then acts as a mechanical barrier to reduce reflux.
Sodium alginate is used in the form of a mixed calcium - sodium salt of alginic acid as a haemostatic and wound dressing ; it is employed in the form of a fibre made into a dressing or packing material.
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