Hydroxy ethyl cellulose (HEC) is a non-ionic water-soluble polymer, white or almost white, odorless, fand ree-flowing granular powder.
The softening temperature of Hydroxy ethyl cellulose is 135 -140 ℃. Under normal circumstances, it is insoluble in most organic solvents, but since the molecule contains the hydrophilic hydroxyethyl, it is easy to dissolve in cold or hot water. The pH value of 2% aqueous solution is 6.5-8.5. With different specifications used, it shows a broad viscosity range. Within the pH range between 2 and 12, there are small changes in the viscosity. Moreover, its solution won’t be affected by the cations, and can coexist with most water-soluble polymers, surfactants , salts. Therefore, it is a fine colloidal thickener able to accommodate the electrolyte solution containing a high concentration.
At high concentrations, it shows non-Newtonian characteristics. The pseudoplastic degree depends mainly on the distribution of substituents. The more uniform the distribution is, the i.e. there is no unsubstituted or inadequately substituted segment or molecular chain, the smaller the thixotropic property will be and the higher the pseudoplastic property will be. At low concentrations, it shows the Newtonian fluid.
In medicine, it is mainly used as thickeners, protective colloids, adhesives, dispersants, stabilizers, suspending agents, film formers and sustained-release materials. It can be used in creams for topical medication, ointments, eye drops, oral liquids, solid tablets, capsules and other dosage forms. Hydroxyethyl cellulose has currently been included in the United States Pharmacopoeia/National Formulary and the European Pharmacopoeia.Select hydroxyethyl cellulose, the biocompatible, hydrophilic, swellable polymer with amorphous characteristics. when it comes into contact with an aqueous medium, it can lead the substrate to swell and form hydrophilicity, such as gelatinous viscous dispersion, and gradually become permeable, so make the drug quantitatively spread. It draws a conclusion from the dissolution analysis the drug system contains a single dose of vancomycin which can maintain the demand for treatment of the drug release up to 48 hours.
In the development of orally sustained and controlled release drug delivery system, due to the lower cost, safety, easy production and other factors, various cellulose derivatives are widely used in the preparation of sustained-release dosage forms, of which cellulose ethers are the most commonly used water-soluble and swellable polymers. It is found out in a comparative study of a series of different cellulose ethers such as hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC) and methyl cellulose (MC) that the physical and chemical factors of the material can affect the drug release kinetics. Of them, HEC is the polymer with the largest hydrophilicity and the maximum erodibility.