Collodions are liquid preparations for external use, containing pyroxylin in a mixture of ethyl ether and ethanol. They are applied to skin by a soft brush or other suitable applicator or rod.

The volatile vehicle ether and ethanol have evaporated; leave a film of pyroxylin on the skin surface.

The collodions are mainly two types:

(i) Medicated: Official medicated collodoin, salicylic acid contains 10% w/v of salicylic acid in flexible collodion USP and is used as kerotolytic agent used in the treatment of corns and warts,

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(ii) Non-medicated: for protection of small cuts and scratches,

Flexibility of collodion is made by addition of castor oil and camphor. Collodion has been used to reduce or eliminate the side effects of fluorouracil treatment of solar keratoses. In salicylic acid preparation, polyacrylic base is used as vehicle.

Pyroxylin is a nitrated cellulose obtained by treating defatted cotton with a mixture of nitric acid and sulphuric acids and its principal constituent is cellulose tetranitrate.. It is high inflammable. It is kept moist with industrial methylated spirit and stored, loosely packed in well-closed containers, protected from light.

Container:

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Collodions are stored in small, wide mouth, screw-capped coloured, fluted glass vial with a brush or applicator within the container or supplied separately.

Label:

‘For External use Only’; ‘Store in a Cool Place’; ‘Highly Inflammable, keep away from naked flames’

Example

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Pyroxyllin 4.0 g

Ether 75.0 ml

Ethanol 25.0 ml

To make about 100.0 ml

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Procedure:

Add the ethanol and ether to the pyroxylin container and closed the container. Shake the mixture occasionally until the pyroxylin is dissolved. Allow to stand for a few days while impurities settle, decant the supernatant liquid because the solution is highly inflammable. Store the preparation in well-closed container with suitable label.