Monograph: |
Agar
Polysaccharides obtained by extracting various species of rhodophyceae algae. The Ph. Eur. Specifies mainly those belonging to the genus gelidium ; the USNF specifies gelidium cartilagineum, Gracilaria confervoides, and related red algae of this class.
Odourless or almost odourless, thin, colourless to pale yellow, yellowish orange, or yellowish grey, translucent strips, flakes, or granules ; tough when damp but becoming more brittle on drying. It is also available in a powdered form. Soluble in boiling water to produce a clear solution that gels on cooling ; practically insoluble in cold water.
Uses and Administration
Agar is used as a suspending or thickening agent in pharmaceutical manufacturing and as an emulsifying and stabilising agent in the food industry.
It was formerly used similarly to methylcellulose as a bulk laxative. Preparations containing agar together with liquid paraffin and phenolphthalein are available to treat constipation, but the relatively small amount of agar in these probably acts solely an emulsion stabiliser.
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