Dimethicone

• BPDimeticone
• Ph. Eur.Dimeticone
• USP–NFDimethicone

dimethylpolysiloxane; dimethylsilicone fluid; dimethylsiloxane polymer; PDMS; polydimethylsiloxane; silicone oil; Q7-9120; Xiameter PMX-200; E900

α-(Trimethylsilyl)-ω-methylpoly[oxy(dimethylsilylene)] · [9006-65-9]

(CH3)3SiO[(CH3)2SiO]nSi(CH3)3 · variable (depends on chain length and viscosity grade)

Semi-solid base, emollient

Typical concentrations: — · Dosage forms: Semi-solid, Liquid

Used as an emollient and water-repellent in topical barrier creams and lotions (often about 10–30% in barrier preparations, and lower in cosmetic emulsions), as an antifoaming agent, as a lubricant for syringes, stoppers and other components, and as a release agent. Mixed with silicon dioxide it forms simethicone, which is used as an antiflatulent and antifoam.

A clear, colourless, odourless, non-volatile liquid. It is a series of linear, fully methylated polysiloxanes end-blocked with trimethylsiloxy groups, available in a wide range of viscosities, typically 20–1300 mm²/s for pharmacopoeial grades.

Viscosity

grade-dependent (for example 20, 100, 350 or 1000 mm²/s); changes relatively little with temperature

Density

about 0.95–0.97 g/cm³

Surface tension

low, about 20–21 mN/m

Refractive index

about 1.40

Solubility

miscible with ethyl acetate, methyl ethyl ketone, toluene and hydrocarbons; very slightly soluble in ethanol; practically insoluble in water

Chemically inert and stable to heat; it can be sterilised by dry heat. Store in a well-closed container.

Compatible with most materials; strong acids and alkalis can degrade it.

Made by hydrolysis of dimethyldichlorosilane together with a small amount of chlorotrimethylsilane as chain terminator, followed by polymerisation and equilibration to the required chain length and removal of volatile low-molecular-weight siloxanes.

Not absorbed after oral or topical administration and regarded as non-toxic and non-irritant to skin; contact with the eyes may cause transient irritation. Injected silicone fluids can cause granulomas and migrate in tissues.

Observe normal precautions for the quantity handled. Spills are very slippery and difficult to remove; use eye protection.

Accepted as a food additive in Europe (E900). Included in the FDA Inactive Ingredient Database (oral capsules, suspensions and tablets; topical and transdermal preparations) and in non-parenteral medicines licensed in Europe.

Cyclomethicone; simethicone; silicone elastomers; hydrophobic colloidal silica.

Choose the viscosity grade for the purpose: low-viscosity grades spread easily and feel light, while higher grades give more durable water-repellent films. Silicone lubrication of prefilled syringes can shed subvisible particles, which matters for protein products, so baked-on silicone or controlled spray levels are often used.