Sodium Alginate

cid3

49,150

Category

Stabilizing Agents; Suspending Agents; Tablet and Capsule Disintegrant; Tablet Binder; Viscosity Increasing Agents

Grade

Pharmceutical Excipients

Description

Sodium alginate occurs as an odorless and tasteless, white to pale yellowish-brown colored powder.

UNII

C269C4G2ZQ

Chemical Name

Sodium alginate

CAS Number

9005-38-3

Synonyms

Alginato sodico; algin; alginic acid, sodium salt; E401; Kelcosol; Keltone; natrii alginas; Protanal; sodium polymannuronate

Administration route

Oral

Dosage Form

Oral suspensions and tablets, oral capsules, modified release tablets, enteric-coated tablets and lozenges

Stability and Storage Conditions

Sodium alginate is a hygroscopic material, although it is stable if stored at low relative humidities and a cool temperature. Aqueous solutions of sodium alginate are most stable at pH 4-10. Below pH 3, alginic acid is precipitated. A 1% w/v aqueous solution of sodium alginate exposed to differing temperatures had a viscosity 60-80% of its original value after storage for 2 years.Solutions should not be stored in metal containers. Sodium alginate solutions are susceptible on storage to microbial spoilage, which may affect solution viscosity. Solutions are ideally sterilized using ethylene oxide, although filtration using a 0.45 mm filter also has only a slight adverse effect on solution viscosity. Heating sodium alginate solutions to temperatures above 70℃ causes depolymerization with a subsequent loss of viscosity.Autoclaving of solutions can cause a decrease in viscosity, which may vary depending upon the nature of any other substances present.Gamma irradiation should not be used to sterilize sodium alginate solutions since this process severely reduces solution viscosity.Preparations for external use may be preserved by the addition of 0.1% chlorocresol, 0.1% chloroxylenol, or parabens. If the medium is acidic, benzoic acid may also be used. The bulk material should be stored in an airtight container in a cool, dry place.

Source and Preparation

Alginic acid is extracted from brown seaweed and is neutralized with sodium bicarbonate to form sodium alginate.

Applications

Sodium alginate is used in a variety of oral and topical pharmaceutical formulations. In tablet formulations, sodium alginate may be used as both a binder and disintegrant; it has been used as a diluent in capsule formulations. Sodium alginate has also been used in the preparation of sustained-release oral formulations since it can delay the dissolution of a drug from tablets, capsules, and aqueous suspensions. The effects of particle size, viscosity and chemical composition of sodium alginate on drug release from matrix tablets have been described. In topical formulations, sodium alginate is widely used as a thickening and suspending agent in a variety of pastes, creams, and gels, and as a stabilizing agent for oil-in-water emulsions. Recently, sodium alginate has been used for the aqueous microencapsulation of drugs, in contrast with the more conventional microencapsulation techniques which use organicsolvent systems. It has also been used in the formation of nanoparticles. The adhesiveness of hydrogels prepared from sodium alginate has been investigated, and drug release from oral mucosal adhesive tablets, buccal gels, and vaginal tablets based on sodium alginate have been reported. The esophageal bioadhesion of sodium alginate suspensions may provide a barrier against gastric reflux or site-specific delivery of therapeutic agents. Other novel delivery systems containing sodium alginate include ophthalmic solutions that form a gel in situ when administered to the eye; an in situ forming gel containing paracetamol for oral administration; nasal delivery systems based on mucoadhesive microspheres; (24) and a freeze-dried device intended for the delivery of bone-growth factors. Hydrogel systems containing alginates have also been investigated for delivery of proteins and peptides.In addition, sodium alginate microspheres have been used in the preparation of a footmouth disease DNA vaccine, and in an oral vaccine for Helicobacter pylori; chitosan nanoparticles coated with sodium alginate may have applications in mucosal vaccine delivery systems. Therapeutically, sodium alginate has been used in combination with an H2-receptor antagonist in the management of gastroeso phageal reflux, and as a hemostatic agent in surgical dressings. Alginate dressings, used to treat exuding wounds, often contain significant amounts of sodium alginate as this improves the gelling properties. Sponges composed of sodium alginate and chitosan produce a sustained drug release and may be useful as wound dressings or as tissue engineering matrices. Lyophilized wound healing wafers composed of sodium alginate have been found to exhibit large reductions in viscosity following gamma irradiation. Sodium alginate is also used in cosmetics and food products.

Safety

Sodium alginate is widely used in cosmetics, food products, and pharmaceutical formulations, such as tablets and topical products, including wound dressings. It is generally regarded as a nontoxic and nonirritant material, although excessive oral consumption may be harmful. A study in five healthy male volunteers fed a daily intake of 175 mg/kg body-weight of sodium alginate for 7 days, followed by a daily intake of 200 mg/kg body-weight of sodium alginate for a further 16 days, showed no significant adverse effects. The WHO has not specified an acceptable daily intake for alginic acid and alginate salts as the levels used in food do not represent a hazard to health. Inhalation of alginate dust may be irritant and has been associated with industrial-related asthma in workers involved in alginate production. However, it appears that the cases of asthma were linked to exposure to seaweed dust rather than pure alginate dust. LD50 (cat, IP): 0.25 g/kg LD50 (mouse, IV): 0.2 g/kg LD50 (rabbit, IV): 0.1 g/kg LD50 (rat, IV): 1 g/kg LD50 (rat, oral): >5 g/kg

Incompatibilities

Sodium alginate is incompatible with acridine derivatives, crystal violet, phenylmercuric acetate and nitrate, calcium salts, heavy metals, and ethanol in concentrations greater than 5%. Low concentrations of electrolytes cause an increase in viscosity but high electrolyte concentrations cause salting-out of sodium alginate; salting-out occurs if more than 4% of sodium chloride is present.