Sodium hyaluronate

• BPSodium Hyaluronate
• JPPurified Sodium Hyaluronate
• Ph. Eur.Sodium Hyaluronate

Hyaluronan; hyaluronic acid sodium salt; hyaluronate sodium; natrii hyaluronas; sodium hyaluronan

Sodium salt of hyaluronic acid, a linear glycosaminoglycan of repeating disaccharide units of D-glucuronic acid and N-acetyl-D-glucosamine linked by alternating β(1→3) and β(1→4) bonds · [9067-32-7]

(C14H20NNaO11)n · repeat unit 401.3; polymer from about 10⁴ to several 10⁶ Da, depending on grade

Gelling agent, viscosity modifier

Typical concentrations: — · Dosage forms: Sterile (parenteral/ophthalmic), Semi-solid

Sodium hyaluronate is used as a viscosity-enhancing and lubricating agent in eye drops and artificial tears (typically about 0.1–0.4%), as a viscoelastic agent in ophthalmic surgery (at higher concentrations, around 1–3%), in intra-articular injections for osteoarthritis, in dermal fillers (usually cross-linked) and in topical wound-healing and moisturising products. It is also investigated as a mucoadhesive carrier and as a targeting ligand in drug delivery systems.

A white or almost white, very hygroscopic powder or fibrous aggregate, odourless. It dissolves slowly in water to give highly viscous, pseudoplastic and viscoelastic solutions; grades are characterised by molecular weight or intrinsic viscosity.

Solubility

sparingly to freely soluble in water depending on molecular weight, dissolving slowly; practically insoluble in acetone and ethanol

pH

about 5.0–8.5 (0.5% w/v aqueous solution)

Rheology

solutions are shear-thinning and viscoelastic; viscosity rises steeply with molecular weight and concentration

Hygroscopicity

very hygroscopic; water content must be controlled

The solid is stable if protected from moisture. In solution the polymer chain is degraded by hyaluronidase, free radicals, heat and extremes of pH, which reduce molecular weight and viscosity; heat sterilisation therefore lowers viscosity, and solutions are often sterile-filtered or processed aseptically. Store in an airtight container protected from light, usually refrigerated or at controlled room temperature as specified by the supplier.

As a polyanion it forms precipitates or complexes with cationic substances such as quaternary ammonium preservatives (for example benzalkonium chloride and cetylpyridinium chloride) at certain concentrations. Oxidising agents and transition metal ions accelerate its depolymerisation.

Produced mainly by fermentation with selected strains of Streptococcus (such as S. equi subsp. zooepidemicus) or recombinant organisms, followed by precipitation, purification and drying. It was formerly extracted from rooster combs; material from animal sources requires additional controls for proteins and viral safety.

Hyaluronic acid is a natural component of connective tissue, synovial fluid and the vitreous humour, and sodium hyaluronate is generally regarded as biocompatible and non-immunogenic. Local reactions such as pain and swelling (including pseudo-septic reactions) have been reported after intra-articular injection, and inflammatory or hypersensitivity reactions after dermal filler use.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

Used in ophthalmic, intra-articular and topical medicines and medical devices licensed in Europe, the USA and elsewhere; many viscoelastic, intra-articular and filler products are regulated as medical devices. It is also used widely in cosmetics.

Hyaluronic acid; cross-linked sodium hyaluronate (hylan); chondroitin sulfate sodium; carbomers.

Specify the molecular weight or intrinsic viscosity range, since this governs viscosity, residence time and biological behaviour. Hydrate the powder slowly without high shear, which can break the polymer chains, and control endotoxin and microbial levels for ophthalmic and parenteral use.