POLYOXYETHYLENE ALKYL ETHERS

Chemical Properties

Polyoxyethylene alkyl ethers vary considerably in their physical appearance from liquids, to pastes, to solid waxy substances. They are colorless, white, cream-colored or pale yellow materials with a slight odor.

Production Methods

Polyoxyethylene alkyl ethers are prepared by the condensation of linear fatty alcohols with ethylene oxide. The reaction is controlled so that the required ether is formed with the polyethylene glycol of the desired molecular weight.

Pharmaceutical Applications

Polyoxyethylene alkyl ethers are nonionic surfactants widely used in topical pharmaceutical formulations and cosmetics, primarily as emulsifying agents for water-in-oil and oil-in-water emulsions, and the stabilization of microemulsions and multiple emulsions.
Polyoxyethylene alkyl ethers are used as solubilizing agents for essential oils, perfumery chemicals, vitamin oils, and drugs of lowwater solubility such as cortisone acetate, griseofulvin, menadione, chlordiazepoxide and cholesterol.They have applications as antidusting agents for powders; wetting and dispersing agents for coarse-particle liquid dispersions; and detergents, especially in shampoos, face washes and similar cosmetic cleaning preparations. They are used as gelling and foaming agents (e.g. Brij 72 gives a quick-breaking foam, while Brij 97 (15–20%), Volpo N series and Cremophor A25 (21–30%) give clear gels).
Polyoxyethylene alkyl ethers have also been used in suppository formulations to increase the drug release from the suppository bases.
Polyoxyethylene alkyl ethers (especially laureth-23) have been used as a solubilizer and coating agent to provide hydrophilicity to polymeric nanoparticles.
Polyoxyethylene alkyl ethers such as polidocanol are suitable for use in injectable formulations as a solubilizer or dispersant.

Safety

Polyoxyethylene alkyl ethers are used as nonionic surfactants in a variety of topical pharmaceutical formulations and cosmetics. The polyoxyethylene alkyl ethers form a series of materials with varying physical properties; manufacturers’ literature should be consulted for information on the applications and safety of specific materials. Although generally regarded as essentially nontoxic and nonirritant materials, some polyoxyethylene alkyl ethers, particularly when used in high concentration (>20%), appear to have a greater irritant potential than others.
Animal toxicity studies suggest that polyoxyethylene alkyl ethers have a similar oral toxicity to other surfactants and can be regarded as being moderately toxic.
(mouse, oral): 2.60 g/kg
(rabbit, skin): 40 g/kg/4 week intermittent
(rat, oral): 2.50 g/kg
Polyoxyethylene lauryl ether:
(mouse, IP): 0.16 g/kg
(mouse, IV): 0.10 g/kg
(mouse, oral): 4.94 g/kg
(mouse, SC): 0.79 g/kg
(rat, IV): 0.027 g/kg
(rat, oral): 8.60 g/kg
(rat, SC): 0.95 g/kg
Polyoxyethylene oleyl ether:
(rat, oral): 25.8 g/kg

storage

Polyoxyethylene alkyl ethers are chemically stable in strongly acidic or alkaline conditions. The presence of strong electrolytes may, however, adversely affect the physical stability of emulsions containing polyoxyethylene alkyl ethers.
On storage, polyoxyethylene alkyl ethers can undergo autoxidation, resulting in the formation of peroxides with an increase in acidity. Many commercially available grades are thus supplied with added antioxidants. Typically, a mixture of 0.01% butylated hydroxyanisole and 0.005% citric acid is used for this purpose.
Polyoxyethylene alkyl ethers should be stored in an airtight container, in a cool, dry place.

Incompatibilities

Discoloration or precipitation may occur with iodides, mercury salts, phenolic substances, salicylates, sulfonamides, and tannins. Polyoxyethylene alkyl ethers are also incompatible with benzocaine, tretinoin and oxidizable drugs.
The antimicrobial efficacy of some phenolic preservatives, such as the parabens, is reduced owing to hydrogen bonding. Cloud points are similarly depressed by phenols owing to hydrogen bonding between ether oxygen atoms and phenolic hydroxyl groups. Salts, other than nitrates, iodides, and thiocyanates (which cause an increase) can also depress cloud points.

Regulatory Status

Included in nonparenteral medicines licensed in the USA and UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.