Product Details

DIMETHICONE

Dimethicone is a silicone-based polymer used as a moisturizer in different skin OTC products.

Dimethicone is approved as a transdermal drug delivery system. Dimethicone 410 is part of the simethicone element in Dow Corning Q7-2242 LVA which is an antifoam.[6, 7] Some OTC's containing dimethicone are used to relieve the discomfort of infant gas caused by air swallowing or certain formulas or food,[8] to prevent and help rash, to protect and relieve chapped or cracked skin[9] and as an anti-lice agent.[10]

Associated Conditions

• Chapped skin
• Diaper Rash
• Dry Skin
• Impetigo caused by Streptococcus aureus
• Impetigo caused by streptococcus pyogenes
• Skin Irritation

Pharmacodynamics

The activity of dimethicone as an anti-flatulent agent prevents the formation of mucus surrounding the gas pockets in the gastrointestinal tract. This allows the formation of big gas bubbles that can be expelled easily. Dimethicone is usually combined with an antacid to confirm the elimination of trapped gas. This particular combination is usually known as simethicone.[3]

The use of dimethicone 410 as an emollient and occlusive agent for the treatment of dry skin conditions has shown to prevent transepidermal water loss which translates into moisturizing of the dry or chapped skin.[11] The effect of dimethicone also reduce flaking and acts as a lubricant which translates into the look of soft, smooth and flexible nature of healthy and young-looking skin.[4]

The use of dimethicone 410 as an anti-lice medication has been reported to effectively cause a lice mortality between 98-100% but the ovicidal effect seems to be limited.[10]

Mechanism of action

Dimethicone, as well as all silicone derivatives, is considered as an occlusive and emollient agent. All occlusive agents act physically blocking transepidermal water loss by the formation of a hydrophobic film on the skin surface and within the superficial interstitium between corneocytes. Simethicone is often combined in drug products with petrolatum, which makes it greasy. The emollient characteristic of dimethicone is performed by filling the space between skin flakes which smooths the skin.[2]

For its use as an anti-flatulent agent, dimethicone 410 acts as an antifoaming agent and it works by reducing the surface tension of gas bubbles. This causes the combination of the bubbles to form larger bubbles in the stomach which can pass easily by means of belching.[3]

The use of dimethicone 410 in anti-lice medication has not been fully elucidated but it seems to be related to the disruption of the water balance mechanism in the lice which leads to the rupture of the gut.[10]

Absorption

The use of dimethicone in skin moisturizers or anti-lice products have proven a very low absorption rate. Studies have indicated that approximately 0.5% of the dose applied to the skin could be considered as bioavailable. When given orally, as it is administered in anti-gas medications, dimethicone 410 is not absorbed or absorbed in very minimal quantities that account only for 0.001-0.2% of the administered dose. Therefore, a minimal to absent dimethicone form can be detected outside of the GI tract.[10]

Volume of distribution

As dimethicone is pharmacologically inert and it is not absorbed, pharmacokinetic studies regarding the volume of distribution are not relevant.

Protein binding

Dimethicone 410 does not bind to plasma proteins as it is not absorbed.

Metabolism

Dimethicone 410 is not metabolized and it is excreted unchanged.[10]

Route of elimination

In preclinical trials of skin preparations, dimethicone 410 was collected in trace levels in feces, expired air and subcutaneous swabs. When given orally, the entire dose of dimethicone can be found unchanged in feces and the recovery can account for even 99.6-99.8% of the administered dose. The limited absorbed dose can be found in urine as unchanged dimethicone.[10]

Half life

As dimethicone is pharmacologically inert and it is not absorbed, pharmacokinetic studies regarding its half-life are not relevant.

Clearance

A very minimal amount of dimethicone is excreted unchanged in urine.[10]

Toxicity

The reported LD50 in preclinical rat studies after oral administration of dimethicones is 4070 mg/Kg.[MSDS] Long-term use of dimethicone in skin products may cause skin irritation and impaired cell development. Under the FDA, dimethicone is considered as a safe substance for human use.[5]

Affected organisms

• Humans and other mammals
• Head lice

SOURCE: DRUGBANK