ГИДРОКСИЭТИЛЦЕЛЛЮЛОЗА

Описание

Hetastarch, another nonproteinaceous colloid, is a complex mixture of ethoxylated amylopectins ranging in molecular weight from 10 to 1,000 kDa (average molecular weight, ~450 kDa). When infused as a 6% solution, hetastarch approximates the activity of human albumin. The larger molecular weights, however, increase its intravascular residence time as well as its plasma expansion effects relative to albumin.
Hetastarch is synthetically produced, so it is degraded more slowly and is less antigenic than other colloids. Despite these advantages, hetastarch is quite expensive and also has no oxygen-carrying capacity.

Химические свойства

Hydroxyethyl cellulose occurs as a white, yellowish-white or grayish-white, odorless and tasteless, hygroscopic powder.

Использование

hydroxyethyl cellulose is a thickener, protective colloid, binder, stabilizer, and suspending agent. It is obtained from wood pulp Copyright 2014 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial Review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. or chemical cotton by treatment with an alkali.

Определение

A starch derivative containing 90% amylopectin.

Подготовка

Hydroxyethylcellulose is prepared from alkali cellulose and ethylene oxide. It may be noted that the hydroxyethyl group itself can react with ethylene oxide so that side-chains of varying length may be present in the product. Commercial materials generally contain between 1.4 and 2.0 ethylene oxide residues per glucose residue and have a degree of substitution of about 0.8-1.0.

Методы производства

A purified form of cellulose is reacted with sodium hydroxide to produce a swollen alkali cellulose, which is chemically more reactive than untreated cellulose. The alkali cellulose is then reacted with ethylene oxide to produce a series of hydroxyethyl cellulose ethers.
The manner in which ethylene oxide is added to cellulose can be described by two terms, the degree of substitution (DS) and the molar substitution (MS). The DS designates the average number of hydroxyl positions on the anhydroglucose unit that have been reacted with ethylene oxide. Since each anhydroglucose unit of the cellulose molecule has three hydroxyl groups, the maximum value for DS is 3. MS is defined as the average number of ethylene oxide molecules that have reacted with each anhydroglucose unit. Once a hydroxyethyl group is attached to each unit, it can further react with additional groups in an end-to-end formation. This reaction can continue and there is no theoretical limit for MS.

Общее описание

Non-ionic water soluble polymer. Aqueous solutions are pseudoplastic. Readily disperses without lumping.

Фармацевтические приложения

Hydroxyethyl cellulose is a nonionic, water-soluble polymer widely used in pharmaceutical formulations. It is primarily used as a thickening agent in ophthalmic and topical formulations, although it is also used as a binder and film-coating agent for tablets.It is present in lubricant preparations for dry eye, contact lens care, and dry mouth.
The concentration of hydroxyethyl cellulose used in a formulation is dependent upon the solvent and the molecular weight of the grade.
Hydroxyethyl cellulose is also widely used in cosmetics.

Безопасность

Hydroxyethyl cellulose is primarily used in ophthalmic and topical pharmaceutical formulations. It is generally regarded as an essentially nontoxic and nonirritant material.
Acute and subacute oral toxicity studies in rats have shown no toxic effects attributable to hydroxyethyl cellulose consumption, the hydroxyethyl cellulose being neither absorbed nor hydrolyzed in the rat gastrointestinal tract. However, although used in oral pharmaceutical formulations, hydroxyethyl cellulose has not been approved for direct use in food products.
Glyoxal-treated hydroxyethyl cellulose is not recommended for use in oral pharmaceutical formulations or topical preparations that may be used on mucous membranes. Hydroxyethyl cellulose is also not recommended for use in parenteral products.

хранилище

Hydroxyethyl cellulose powder is a stable though hygroscopic material.
Aqueous solutions of hydroxyethyl cellulose are relatively stable at pH 2–12 with the viscosity of solutions being largely unaffected. However, solutions are less stable below pH 5 owing to hydrolysis. At high pH, oxidation may occur.
Increasing the temperature reduces the viscosity of aqueous hydroxyethyl cellulose solutions. However, on cooling, the original viscosity is restored. Solutions may be subjected to freeze–thawing, high-temperature storage, or boiling without precipitation or gelation occurring.
Hydroxyethyl cellulose is subject to enzymatic degradation, with consequent loss in viscosity of its solutions. Enzymes that catalyze this degradation are produced by many bacteria and fungi present in the environment. For prolonged storage, an antimicrobial preservative should therefore be added to aqueous solutions. Aqueous solutions of hydroxyethyl cellulose may also be sterilized by autoclaving.
Hydroxyethyl cellulose powder should be stored in a well-closed container, in a cool, dry place.

Несовместимости

Hydroxyethyl cellulose is insoluble in most organic solvents. It is incompatible with zein and partially compatible with the following water-soluble compounds: casein; gelatin; methylcellulose; polyvinyl alcohol, and starch.
Hydroxyethyl cellulose can be used with a wide variety of watersoluble antimicrobial preservatives. However, sodium pentachlorophenate produces an immediate increase in viscosity when added to hydroxyethyl cellulose solutions.
Hydroxyethyl cellulose has good tolerance for dissolved electrolytes, although it may be salted out of solution when mixed with certain salt solutions. For example, the following salt solutions will precipitate a 10% w/v solution of Cellosize WP-09 and a 2% w/v solution of Cellosize WP-4400: sodium carbonate 50% and saturated solutions of aluminum sulfate; ammonium sulfate; chromic sulfate; disodium phosphate; magnesium sulfate; potassium ferrocyanide; sodium sulfate; sodium sulfite; sodium thiosulfate; and zinc sulfate.
Natrosol is soluble in most 10% salt solutions, excluding sodium carbonate and sodium sulfate, and many 50% salt solutions with the exception of the following: aluminum sulfate; ammonium sulfate; diammonium phosphate; disodium phosphate; ferric chloride; magnesium sulfate; potassium ferrocyanide; sodium metaborate; sodium nitrate; sodium sulfite; trisodium phosphate; and zinc sulfate. Natrosol 150 is generally more tolerant of dissolved salts than is Natrosol 250.
Hydroxyethyl cellulose is also incompatible with certain fluorescent dyes or optical brighteners, and certain quaternary disinfectants which will increase the viscosity of aqueous solutions.

Регуляторный статус

Included in the FDA Inactive Ingredients Database (ophthalmic preparations; oral syrups and tablets; otic and topical preparations). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Hydroxyethyl cellulose is not currently approved for use in food products in Europe or the USA, although it is permitted for use in indirect applications such as packaging. This restriction is due to the high levels of ethylene glycol residues that are formed during the manufacturing process.