Sodium starch glycolate

• BPSodium Starch Glycolate
• Ph. Eur.Sodium Starch Glycolate
• USP–NFSodium Starch Glycolate

Carboxymethyl starch, sodium salt; carboxymethylamylum natricum; Explotab; Glycolys; Primojel; sodium carboxymethyl starch; Vivastar P

Sodium carboxymethyl ether of starch, usually cross-linked (prepared mainly from potato starch) · [9063-38-1]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Disintegrant

Typical concentrations: 2–8% · Dosage forms: Solid

Sodium starch glycolate is a 'superdisintegrant' used in oral tablets and capsules prepared by direct compression or wet granulation. Usual concentrations are 2–8% w/w, with about 4% often optimal; higher levels can slow disintegration because the swollen gel blocks further water uptake. It may be added intragranularly, extragranularly or split between the two.

A white or almost white, odourless, tasteless, free-flowing, very hygroscopic powder made up of oval or spherical granules. The pharmacopoeias describe types that differ in pH and sodium content (Ph. Eur. Types A, B and C; USP–NF Types A and B).

pH

Type A 5.5–7.5; Type B 3.0–5.0 (aqueous dispersion)

Sodium content

Type A 2.8–4.2%; Type B 2.0–3.4% (dried basis)

Loss on drying

not more than 10% w/w

Swelling

swells rapidly in water to many times its original volume (up to about 300-fold) without dissolving

Solubility

practically insoluble in water and in most organic solvents; forms a translucent suspension in water

Stable, but very hygroscopic. Store in a well-closed container to protect it from wide variations in humidity and temperature, which can cause caking. Tablets containing it may harden on storage at high humidity.

Incompatible with ascorbic acid. Its disintegrant efficiency can be reduced by high concentrations of hydrophobic lubricants, by some highly soluble or hygroscopic excipients, and by high compression forces. As an anionic polymer it may bind some cationic drugs.

Starch (usually potato starch) is cross-linked, either chemically (for example with sodium trimetaphosphate) or by dehydration, and then carboxymethylated by reaction with sodium monochloroacetate in an alkaline alcoholic medium. The product is neutralised with an acid such as citric acid, washed with aqueous alcohol to remove sodium chloride and glycolate by-products, and dried.

Widely used in oral products and generally regarded as non-toxic and non-irritant. Very large oral amounts may be harmful, but such quantities are far above those used in formulations.

Observe normal precautions for the quantity handled. Avoid dust generation; eye protection, gloves and a dust mask are recommended.

Included in the FDA Inactive Ingredient Database (oral capsules and tablets) and in non-parenteral medicines licensed in Europe.

Croscarmellose sodium; crospovidone; pregelatinised starch; starch.

Its rapid swelling with little gel formation makes it effective at low levels, but performance varies with degree of substitution, cross-linking and particle size, so the source and grade should be specified. It is less affected by wet granulation than many disintegrants, though some loss of efficiency can occur.