Polyoxyethylene Stearates

Synonyms:

Ethoxylated fatty acid esters; macrogol stearates; Marlosol; PEG fatty acid esters; PEG stearates; polyethylene glycol stearates; poly(oxy-1,2-ethanediyl) a-hydro-o-hydroxyoctadecanoate; polyoxyethylene glycol stearates. Polyoxyethylene stearates are nonionic surfactants produced by polyethoxylation of stearic acid. Two systems of nomenclature are used for these materials. The number ‘8’ in the names ‘poloxyl 8 stearate’ or ‘polyoxyethylene 8 stearate’ refers to the approximate polymer length in oxyethylene units. The same material may also be designated ‘polyoxyethylene glycol 400 stearate’ or ‘macrogol stearate 400’ in which case, the number ‘400’ refers to the average molecular weight of the polymer chain

Description: 

Chemical Name: Polyethylene glycol stearate 
Polyethylene glycol distearate

Emulsifying agent; solubilizing agent; wetting agent.

• Polyoxyethylene stearates are generally used as emulsifiers in oil-inwater-type creams and lotions.

• Their hydrophilicity or lipophilicity depends on the number of ethylene oxide units present: the larger the number, the greater the hydrophilic properties.

• Polyoxyl 40 stearate has been used as an emulsifying agent in intravenous infusions.

• Polyoxyethylene stearates are particularly useful as emulsifying agents when astringent salts or other strong electrolytes are present.

• They can also be blended with other surfactants to obtain any hydrophilic–lipophilic balance for lotions or ointment formulations.

Polyoxyethylene stearates are unstable in hot alkaline solutions owing to hydrolysis, and will also saponify with strong acids or bases. Discoloration or precipitation can occur with salicylates, phenolic substances, iodine salts, and salts of bismuth, silver, and tannins. Complex formation with preservatives may also occur. The antimicrobial activity of some materials such as bacitracin, chloramphenicol, phenoxymethylpenicillin, sodium penicillin, and tetracycline may be reduced in the presence of polyoxyethylene stearate concentrations greater than 5% w/w.

Although polyoxyethylene stearates are primarily used as emulsifying agents in topical pharmaceutical formulations, certain materials, particularly polyoxyl 40 stearate, have also been used in intravenous injections and oral preparations.

Observe normal precautions appropriate to the circumstances and quantity of material handled. Polyoxyethylene stearates that contain greater than 100 ppm of free ethylene oxide may present an explosion hazard when stored in a closed container. This is due to the release of ethylene oxide into the container headspace, where it can accumulate and so exceed the explosion limit.

Polyethylene glycol; stearic acid.