Polyoxyl 40 stearate

• BPMacrogol Stearate
• JPPolyoxyl 40 Stearate
• Ph. Eur.Macrogol Stearate
• USP–NFPolyoxyl 40 Stearate

Macrogol stearate 2000; Myrj S40; Myrj 52; PEG-40 stearate; polyethylene glycol stearate; polyoxyethylene 40 stearate

α-Hydro-ω-hydroxypoly(oxy-1,2-ethanediyl) octadecanoate (mixture of mono- and diesters of stearic acid with polyethylene glycol) · [9004-99-3]

C17H35COO(CH2CH2O)nH, n ≈ 40 · ≈ 2 000

Surfactant, emulsifier

Typical concentrations: — · Dosage forms: Semi-solid

A hydrophilic nonionic surfactant used mainly as an emulsifier in oil-in-water creams and lotions, often combined with a lipophilic co-emulsifier such as glyceryl monostearate or cetyl alcohol, and also as a solubiliser and wetting agent. It has been used in tablet film coatings and as a lubricant or release aid in some tablets. Typical levels: emulsifying agent about 0.5–10%, solubilising agent about 1–10%, wetting agent about 0.1–3%.

A mixture of mono- and diesters of mainly stearic and palmitic acids with polyethylene glycol having an average of about 40 oxyethylene units, together with some free polyethylene glycol. It is a white to light tan waxy solid with a faint, fat-like odour.

Physical form

white to light tan, waxy solid or flakes with a faint fatty odour

HLB

about 16.9

Congealing range

about 39–44 °C

Saponification value

about 25–35

Solubility

soluble in water, ethanol and acetone; insoluble in mineral oil and vegetable oils

Stable in the presence of electrolytes and weak acids or bases, but strong acids and alkalis cause gradual hydrolysis (saponification) of the ester. Store in a well-closed container in a cool, dry place.

Discoloration or precipitation can occur with salicylates, phenols, iodine salts and salts of bismuth, silver and mercury, and with tannins. It can reduce the activity of antimicrobial preservatives such as parabens and phenols.

Prepared either by direct reaction of stearic acid with ethylene oxide or by esterifying polyethylene glycol with stearic acid.

Used in oral, topical and some parenteral products and generally regarded as non-toxic and non-irritant at the levels used, although occasional skin sensitivity has been reported.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

Included in the FDA Inactive Ingredient Database (oral tablets and other oral forms; topical preparations) and in non-parenteral medicines licensed in Europe.

Polyoxyl 8 stearate; polyoxyl 50 stearate; polyoxyethylene alkyl ethers; polysorbates.

The Ph. Eur. monograph covers macrogol stearates of several chain lengths, distinguished by the nominal number of oxyethylene units, so the type equivalent to polyoxyl 40 stearate should be specified. Being an ester, it is best kept away from formulations at extreme pH.