Monograph: |
Methylpolysiloxane
The properties are same as dimethicone hcl, so see below at dimethicone hcl record for the
details.
Dimethicone
Dimethicones are fluid silicones in which the organic group is
a methyl radical. The Ph. Eur. describes dimethicones with a
kinematic viscosity between 20 and 1300innr per second,
those with a nominal viscosity of 50 sq.mm per second or less
being intended for external use. The USNF allows a range of
nominal viscosities between 20 and 30 000 centistokes.
Dimethicones are clear colourless, odourless liquids. Practi-
cally Insoluble in water, acetone, and methyl alcohol: very
slightly soluble to practically insoluble in dehydrated alcohol;
miscible with ethyl acetate, methyl ethyl ketone. and toluene;
very slightly soluble in isopropyl alcohol: soluble in amyl ac-
etate, chlorinated hydrocarbons, ether, n-hexane. petroleum
spirit, and xylene. Store in airtight containers,
Simethicone (activated dimethicone) is a mixture of liquid
dimethicones with silicon dioxide.
Adverse Effects
Adverse effects from the clinical use of silicones appear to be
rare. Foreign-body reactions have been reported following
their use as joint implants. Other implants, notably breast im-
plants, usually for reconstruction following mastectomy or
for cosmetic purposes, carry the risk of migration of silicone
with cyst formation and other complications: accidental intra-
vascular injection has been fatal. Late adverse ocular effects
can follow the intravitreal injection of liquid silicone in the
management of retinal detachment.
Connective tissue disorders. Since the introduction of
silicone breast implants in the early 1960s there have been
numerous anecdotal reports of various connective-tissue dis-
orders occurring in women who have undergone breast recon-
struction or augmentation with these implants. Scleroderma
has been the most frequently reported disorder, others have
included systemic lupus erythematosus. rheumatoid arthritis.
and inflammatory myopathies. A syndrome of vague muscu-
loskeletal symptoms, fever, and fatigue has also been report-
ed. These cases led the PDA to call for a moratorium in the
US on the use of silicone breast implants in January 1992.
However, with the exception of one study of self-reported
symptoms which showed only a small increase in risk, large
epidemiological studies and a review by the Medical De-
vices Agency in the UK have so far failed to show any asso-
ciation between silicone breast implants and connective-
tissue disorders.
Uses and Administration
Dimethicones and other silicones are water-repellent and
have a low surface tension. They are used in topical barrier
preparations for protecting the skin against water-soluble irri-
tants. Creams, lotions, and ointments containing, a dime-
thicone are employed for the prevention of bedsores and
napkin rash and to protect the skin against trauma due to in-
continence or stoma discharge. Silicone preparations should
not be applied where free drainage is necessary or to inflamed
or abreded skin. Silicones, usually a dimethicone, are also
used topically as wound dressings.
Silicones have also been used for arthroplasty in rheumatic
disorders, by intravitreal injection for retinal detachment, and
by subcutaneous injection or implantation in reconstructive or
cosmetic surgery.
Dimethicones, in particular dimethicone(activated dime-
thicone) are used in the treatment of flatulence.
Retinal detachment. Retinal detachment is separation of
the retina from the underlying retinal pigmentary epithelium
and usually requires surgical repair. Intravitreal injection of
liquid silicone may be used for retinal tamponade following
or in conjunction with surgery in complicated or persistent
detachment of the retina. Late complications following its
use may include cataract, glaucoma, and keratopathy.
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