USES: HC are use mainly for their emollient effect and not intended for penetration into the skin. They are difficult to wash off. They do not “dry out” or change noticeably upon aging.
The components of the ointment are mixed together by various means until a uniform preparation has been attained.
In small scale or in extemporaneous compounding of the Rx, the pharmacist may use 2 means:
In preparing ointment by spatulation, the pharmacist works the ointment with a stainless steel spatula but if the components react with metal (such as iodine, tannins, mercuric salts) the hard rubber is used
Liquid substances or solutions of drugs are added to an ointment only after due consideration of the ointment nature.
An aqueous solution would be added with difficulty to the oleaginous ointment, except in very small amount. However, water absorbable hydrophilic ointment bases would be quite suitable for the absorption and incorporation of the aqueous solution.
In case of hydrophobic base and an aqueous solution is to be added, a portion of the hydrophobic base is replaced by a hydrophilic base.
By this method, all or some of the components of an ointment are combined by melting together and cooled with constant stirring until congeal.
Those components not melted are generally added to the congealing mixture as it is cooled and stirred.
The heat labile substances and volatile constituents are added last when temperature is low enough not to cause decomposition.
Semisolid pharmaceuticals frequently either in jars or in tubes. The jars may be made of glass, uncolored, colored green, amber or blue or opaque and porcelain white. Plastic jars are used in limited extent. The tubes are made of tin or plastic. These are called “collapsible tube”.
– methylparaben,propyl paraben, phenols, benzoic acid, sorbic,quaternary ammonium salts
Example: Betamethasone Valerate Ointment — must be absence of Staphylococcus aureus and Pseudomonas aeriginosa