Hydroxyethyl cellulose

• BPHydroxyethylcellulose
• Ph. Eur.Hydroxyethylcellulose
• USP–NFHydroxyethyl Cellulose

Cellosize HEC; cellulose hydroxyethyl ether; HEC; hydroxyethylcellulosum; Natrosol; Tylose H

Cellulose, 2-hydroxyethyl ether · [9004-62-0]

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

Gelling agent, viscosity modifier

Typical concentrations: — · Dosage forms: Liquid, Semi-solid

A non-ionic, water-soluble polymer used mainly as a thickening and suspending agent in ophthalmic and topical products, including gels, lubricating jellies, lotions and artificial tears, usually at concentrations of a few per cent or less. It is also used as a binder and film former in tablets, as a matrix former in sustained-release systems, as a stabiliser in emulsions and in mucoadhesive formulations. It is widely used in cosmetics and toiletries.

A white, yellowish-white or greyish-white, odourless and tasteless, hygroscopic powder or granules. Grades are distinguished by the viscosity of their aqueous solutions and by the degree of hydroxyethyl substitution.

Molar substitution

typically about 1.5–3.5 (≈ 2.5 for common grades)

pH

5.5–8.5 (1% w/v aqueous solution)

Viscosity

wide range of grades, from a few mPa·s to many thousands of mPa·s for 1–2% w/v solutions

Solubility

soluble in hot and cold water, without thermal gelation; practically insoluble in acetone, ethanol and most other organic solvents

The powder is stable but hygroscopic; store in a well-closed container in a cool, dry place. Aqueous solutions are relatively stable at pH 2–12, but viscosity falls through acid hydrolysis at low pH and oxidative degradation at high pH. Solutions are susceptible to enzymatic (cellulase) degradation and should be preserved.

Compatible with most water-soluble gums and resins and, being non-ionic, tolerates many salts, although very high salt concentrations can salt it out. It is incompatible with zein and may be precipitated by some concentrated solutions of salts such as sodium sulfate.

Prepared by treating purified cellulose with sodium hydroxide to form alkali cellulose, which is then reacted with ethylene oxide. The product is neutralised, washed, dried and milled.

Regarded as essentially non-toxic and non-irritant; it is not absorbed from the gastrointestinal tract. It is used in ophthalmic preparations and contact lens solutions without significant irritation.

Observe normal precautions for the quantity handled. The fine powder can form explosive dust–air mixtures; avoid generating dust and use eye protection and gloves.

Included in the FDA Inactive Ingredient Database (ophthalmic, otic, oral, topical and vaginal preparations) and in non-parenteral medicines licensed in Europe.

Ethylhydroxyethyl cellulose; hydroxypropyl cellulose; hypromellose; methylcellulose.

Unlike methylcellulose and hypromellose, hydroxyethyl cellulose does not gel on heating, so it can be dissolved directly in hot water. To prevent lumps, disperse the powder in water with good agitation before the pH is raised or before other solutes are added; some grades are surface-treated to delay hydration and ease dispersion.