Pharmaceutical Agar

Pharmaceutical Agar

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Agar occurs as transparent, odorless, tasteless strips or as a coarse or fine powder. It may be weak yellowish-orange, yellowish-gray to pale-yellow colored, or colorless. Agar is tough when damp, brittle when dry.

Nonproprietary Names

  • JP: Agar
  • PhEur: Agar
  • USP-NF: Agar
 Pharmaceutical Agar

Synonyms: Agar-agar; agar-agar flake; agar-agar gum; Bengal gelatin; Bengal gum; Bengal isinglass; Ceylon isinglass; Chinese isinglass; E406; gelosa; gelose; Japan agar; Japan isinglass; layor carang.

Chemical Name and CAS Registry Number

  • Agar [9002-18-0]

Structural Formula
Agar is a dried, hydrophilic, colloidal polysaccharide complex extracted from the agarocytes of algae of the Rhodophyceae. The structure is believed to be a complex range of polysaccharide chains having alternating a-(1,3) and b-(1,4) linkages. There are three extremes of structure noted: namely neutral agarose; pyruvated agarose having little sulfation; and a sulfated galactan. Agar can be separated into a natural gelling fraction, agarose, and a sulfated nongelling fraction, agaropectin

Functional Category
Emulsifying agent; stabilizing agent; suppository base; suspending agent; sustained-release agent; tablet binder; thickening agent; viscosity-increasing agent.

Applications in Pharmaceutical Formulation or Technology

Agar is widely used in food applications as a stabilizing agent. In pharmaceutical applications, agar is used in a handful of oral tablet and topical formulations. It has also been investigated in a number of experimental pharmaceutical applications including as a sustained-release agent in gels, beads, microspheres, and tablets. It has also been reported to work as a disintegrant in tablets.

Agar has been used in a floating controlled-release tablet; the buoyancy in part being attributed to air entrapped in the agar gel network. It can be used as a viscosity-increasing agent in aqueous systems. Agar can also be used as a base for nonmelting, and nondisintegrating suppositories.  Agar has an application as a suspending agent in pharmaceutical suspensions.


Method of Manufacture: Agar is obtained by freeze-drying a mucilage derived from Gelidium amansii Lamouroux, other species of the same family (Gelidiaceae), or other red algae (Rhodophyta).


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