Description
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.
Characteristics
Hydroxyethyl cellulose is soluble in hot or cold water, and does not precipitate at high temperature or boiling, so it has a wide range of solubility and viscosity characteristics, as well as non-thermal gelling properties. Hydroxyethyl cellulose is a non-ionic polymer material , can coexist with a wide range of other water-soluble polymers, surfactants, and salts, and is an excellent colloidal thickener for high-concentration dielectric solutions. The water retention capacity of hydroxyethyl cellulose is twice that of methyl cellulose, and it has better flow regulation; the dispersing ability of hydroxyethyl cellulose is comparable to that of methyl cellulose and hydroxypropyl methyl cellulose The specific dispersing ability is the worst, but the protective colloid ability is the strongest.
Preparation
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.
Brand name
Hespan (DuPont Merck)
.
General Description
Non-ionic water soluble polymer. Aqueous solutions are pseudoplastic. Readily disperses without lumping.
Pharmaceutical Applications
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.
Toxicology
Considered to be non toxic. Use as a food additive indicates good tolerance of small amounts, but excessive amounts or overuse may bring irritant and /or harmful effects. Polysaccharides are not substantially absorbed from the gastrointestinal tract but may produce a laxative effect.
Safety
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.
storage
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.
Properties and Applications
|
Index
|
Results
|
|
Appearance
|
White powder
|
|
Viscosity(mPa.s) 2% at 20℃,Brookfield 20rpm sp.5 cps
|
15,000-25,000
|
|
Particle size 80 mesh (180um) %
|
95.0 min
|
|
M.S.(Molar substitution degree) %
|
2.0-2.5
|
|
Moisture
％
|
≤6.0
|
|
Water insoluble %
|
≤0.5
|
|
pH
|
5.5-7.0
|
|
Ash Content %
|
≤5.0
|
|
Bulk density g/L
|
420-500
|
Incompatibilities
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.
Regulatory Status
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.
