Carrageenan

Category

Emulsifying Agents; Stabilizing Agents; Suspending Agents; Sustained-release Agents; Viscosity-increasing Agents

Grade

Pharmceutical Excipients

Description

Carrageenan, when extracted from the appropriate seaweed source, is a yellow-brown to white colored, coarse to fine powder that is odorless and tasteless.

UNII

5C69YCD2YJ

Synonyms

Chondrus extract; E407; Gelcarin; Genu; Grindsted; Hygum TP-1; Irish moss extract; Marine Colloids; SeaSpen PF; Viscarin

Stability and Storage Conditions

Carrageenan is a stable, though hygroscopic, polysaccharide and should be stored in a cool, dry place. Carrageenan in solution has maximum stability at pH 9 and should not be heat processed at pH values below 3.5. Acid and oxidizing agents may hydrolyze carrageenan in solution leading to loss of physical properties through cleavage of glycosidic bonds. Acid hydrolysis depends on pH, temperature and time. The acid hydrolysis takes place only when the carrageenan is dissolved, and the hydrolysis is accelerated as the processing temperature and/or the processing time is increased. However, when the carrageenan is in its gelled state the acid hydrolysis no longer takes place.

Source and Preparation

The main species of seaweed from which carrageenan is manufactured are Eucheuma, Chondrus, and Gigartina. The weed is dried quickly to prevent degradation, and is then baled for shipment to processing facilities. The seaweed is repeatedly washed to remove gross impurities such as sand, salt, and marine life, and then undergoes a hot alkali extraction process, releasing the carrageenan from the cell.

Applications

Carrageenan is used in a variety of nonparenteral dosage forms, including suspensions (wet and reconstitutable), emulsions, gels, creams, lotions, eye drops, suppositories, tablets, and capsules. In suspension formulations, usually only the ι-carrageenen and λ-carrageenan fractions are used. λ-Carrageenan is generally used at levels of 0.7% w/v or less, and provides viscosity to the liquid. Carrageenan has been shown to mask the chalkiness of antacid suspensions when used as a suspending agent in these preparations.(2) When used in concentrations of 0.1-0.5%, carrageenan gives stable emulsions.

Safety

Carrageenan is widely used in numerous food applications and is increasingly being used in pharmaceutical formulations. Carrageenan is generally regarded as a relatively nontoxic and nonirritating material when used in nonparenteral pharmaceutical formulations.However, carrageenan is known to induce inflammatory responses in laboratory animals, and for this reason it is frequently used in experiments for the investigation of anti-inflammatory drugs. Animal studies suggest that degraded carrageenan (which is not approved for use in food products) may be associated with cancer in the intestinal tract, although comparable evidence does not exist in humans. The WHO has set an acceptable daily intake of carrageenan of ‘not specified’ as the total daily intake was not considered to represent a hazard to health.In the UK, the Food Advisory Committee has recommended that carrageenan should not be used as an additive for infant formulas. LD50 (rat, oral): >5 g/kg LD50 (rabbit, skin): >2 g/kg/4 h LC50 (rat, inhalation): >0.93 mg/L

Incompatibilities

Carrageenan can react with cationic materials. If complexation of cationic materials, with associated modification of the active compound’s solubility, is undesirable, the use of carrageenan is not recommended. Carrageenan may interact with other charged macromolecules, e.g. proteins, to give various effects such as viscosity increase, gel formation, stabilization or precipitation.