Polysilicone-15

Identification

Generic Name

Polysilicone-15

DrugBank Accession Number

DB11271

Background

Polysilicone-15 is a silicone based UVB absorber ^2,3,4,7,8,9. The compound is a colorless to pale yellow viscous liquid which is soluble in organic solvents of medium polarity and insoluble in water ^2,3,4,7,8,9. It is the first polymeric UVB filer consisting of chromophores attached to a silicone backbone ^2,3,4,7,8,9. When included in various other cosmetic shampoos, conditioners, or hairsprays the compound also functions as an effective photostabilizer of the product ^2,3,4,7,8,9.

Type

Small Molecule

Groups

Approved

Synonyms

Diethylbenzylidene malonate dimethicone
Diethylmalonylbenzylidene oxypropene dimethicone
Dimethicodiethylbenzalmalonate

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Pharmacology

Indication

Polysilicone-15 is used as an UV-filter in cosmetic sunscreen products as well as in other cosmetic products (like shampoos, conditioners, hairsprays, etc.) where it can confer photostability to the product(s) ^4,9.

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Associated Conditions

Indication Type	Indication	Combined Product Details	Approval Level	Age Group	Patient Characteristics	Dose Form
Prevention of	Sunburn		••• •••

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Pharmacodynamics

As an active ingredient in sunscreen products, polysilicone-15 is applied directly onto human skin where it acts as a chemical sunscreen layer between skin and sunlight that also directly absorbs the UV sunlight radiation ^2,3,4,7,8,9. When used in combination with other ingredients in cosmetic shampoos, conditioners, hairsprays, etc. the photostable polysilicone-15 confers photostability onto the entire combined product, protecting it from deterioration in the sunlight by absorbing the UV light radiation ^4,9. Additionally, there have been studies suggesting polysilicone-15 is also considered to have little to no absorption through the skin ², so little systemic exposure and pharmacokinetics are expected and users can freely wash off and re-apply the compound as necessary.

Mechanism of action

Ultraviolet radiation is the invisible energy component to sunlight and consists of three wavelength ranges:

(a) UVA is long-range UV radiation between 320-400nm ⁶. Although not as energetic as UVB, UVA can penetrate deep into the dermis ⁶. UVA can cause immediate tanning, premature skin aging, and can also play a role in the formation of some skin cancers ⁶. Approximately 95% of UVA from the sun passes through Earth's ozone layer ⁶.

(b) UVB is short-wavelength UV radiation between 280-320nm ⁶. It is capable of penetrating the outer protective layer of the skin and is responsible for delayed tanning, sunburns, and most skin cancers ⁶. A large amount of UVB is absorbed by the ozone layer, however, as only 5% reaches the Earth's surface ⁶.

(c) UVC is comprised of wavelengths between 100-280nm and is very energetic ⁶. It is very dangerous to all forms of life, even when the exposure is short ⁶. However, UVC radiation is generally filtered out by the ozone layer and never reaches the Earth ⁶.

Ultimately, the shorter the wavelength, the more harmful the UV radiation - although shorter wavelength UV radiation is less able to penetrate the skin ⁶.

Polysilicone-15 is comprised of chromophores that are attached to polysiloxane chains in a controlled manner with optimal micro-distance between chromophores ⁸. This arrangement forms a flexible film that disperses the chromophores in a way that effectively falls into and flows about the natural ergonomics of the skin surface - as opposed to how conventional UV filters tend to accumulate in the troughs of the skin ⁸. Regardless, polysilicone-15 is specifically a UVB filter and is often combined with other approved UV filters to achieve a wide range of UV protection ⁸.

Finally, polysilicone-15 is itself photostable, containing specialized chemicals that take excited state energy away from molecules of the compound that have absorbed high-energy UV light particles and return the molecules to the ground state, ready to absorb more UV radiation and having been spared from various photochemical reactions that would have been facilitated by the retention of the high energy UV radiation, had it not been neutralized by the photostabilizer chemicals ⁵. When combined with other ingredients in cosmetic shampoo, conditioner, and hairspray products this photostability is conferred upon the entire combination product, allowing the product to remain intact after it has been applied to hair and exposed to sunlight outdoors ^4,9.

Absorption

Polysilicone-15 is reported as having little to no absorption through the skin ^2,8. At this time, however, studies demonstrate that the components of most commonly used sunscreens are likely absorbed into the skin at least to some extent - although penetration to deeper tissues and the cutaneous circulation remains limited ¹. Despite the extensive use of sunscreen products around the world, there have been few reports of adverse effects related to their use ¹.

Volume of distribution