Carrageenan

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

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.

Chemical Name:  Carrageenan

Emulsifying agent; gel base; stabilizing agent; suspending agent;
sustained-release agent; viscosity-increasing agent.

• 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 i-carrageenen and lcarrageenan fractions are used.

• l-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.

• When used in concentrations of 0.1–0.5%, carrageenan gives stable emulsions. Carrageenan is used in hand lotions and creams to provide slip and improved ‘rub out’.

• i-Carrageenan develops a shear-thinning thixotropic gel, which can be easily poured after shaking.

• When i-carrageenan is used, the presence of calcium ions is required for the gel network to become established. With pure i-carrageenan, about 0.4% w/v is required for most suspensions plus the addition of calcium.

• However, if SeaSpen PF is used, it must be at about 0.75% w/v level, although no additional calcium is required as this is already present in the product to control the rate of gelation.

• Studies on the effect of carrageenan and other colloids on mucoadhesion of drugs to the oropharyngeal areas have shown that carrageenan had the greatest propensity for adhesion and can be used in formulations for oral and buccal drug delivery.

• The application of carrageenan in topical gel bases has been examined, and the findings indicate that the use of carrageenan in these dosage forms is most likely to be dependent on the active drug, owing to the potential for ionic interactions.

• In the case of topical gels, a combination of i, k-, and lcarrageenans produces a spreadable gel with acceptable tactile sensation, resulting in drug release that is more likely to follow diffusion kinetics.

• Incorporation of carrageenan into tablet matrices with various drugs and other excipients to alter release profiles has been studied, illustrating that the carrageenans have good tablet-binding properties.

• Furthermore, the inclusion of calcium or potassium salts into the tablet creates a microenvironment for gelation to occur, which further controls drug release.

• There have also been several references to the use of carrageenan in chewable tablets having a confectionary texture.

• This approach to creating a novel dosage form requires the use of both icarrageenan and k-carrageenan, to prevent moisture loss and texture changes that occur over time.

• Carrageenan has been used for the microencapsulation of proteins and probiotic bacteria.

• Hydrogels have also been prepared by crosslinking with gelatin and k-carrageenan for oral delivery of probiotic bacteria.

• It has also been used as beads in the preparation of controlled release systems.

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.

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

Observe normal precautions appropriate to the circumstances and quantity of material handled.

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