Ointments

Ointments are semisolid preparations intended for external use. They are easily spread. Ointments are typically used as emolients (to make the skin more pliable), protective barriers (to prevent harmful substances from coming in contact with the skin), and vehicles for the incorporated medication. Ointments are characterized as being oleaginous in nature.

There are two main types of ointment bases. Hydrophobic bases feel greasy and contain mixtures of fats, oils, and waxes. Hydrophobic bases cannot be washed off using water. Hydrophilic bases are usually emulsion bases. The o/w–type bases can be easily washed off with water, but the w/o–type emulsion bases are slightly more difficult to remove.

Oleaginous bases include petrolatum, synthetic esters, and lanolin derivatives. Petrolatum is a good base for oil–insoluble ingredients. It forms an occlusive film on the skin, absorbs less than 5% water under normal conditions, and does not become rancid. Wax can be incorporated to stiffen the base. Synthetic esters are used as constituents of oleaginous bases. These esters include glyceryl monostearate, isopropyl palmitate, butyl stearate, and butyl palmitate. Lanolin derivatives are often used in topical and cosmetic preparations. Examples are lanolin oil and hydrogenated lanolin.

Absorption bases are anhydrous and insoluble in water. Therefore, they are not washable in water, though they can absorb water. A base consisting primarily of a mixture of animal sterols with petrolatum jelly is generally classified as an absorption base. A hydrophilic ointment is an o/w emulsion that uses sodium lauryl sulfate as an emulsifying agent. It is readily miscible with water and is removed from the skin easily.

Based on their penetration, ointment bases have been placed into three classes: epidermic (petrolatum, waxes and their combinations), endodermic (vegetable oils, lanolin, wool fat (anhydrous lanolin) and their combinations, and diadermic (emulsions and water–soluble bases).

Medicinal substances may be incorporated into an ointment base by levigation or by the fusion method. Insoluble substances should be comminuted to a fine powder and levigated before incorporation with a small amount of a compatible levigating agent or with the base itself. Levigation is performed on an ointment slab with a stainless steel spatula with a long, broad, flexible blade. If the substance may interact with a metal spatula (e.g., when incorporating iodine or mercuric salts), then a hard rubber spatula can be used. Insoluble substances should be powdered finely in a mortar and mixed with an equal quantity of base until a smooth, grit–free mixture is obtained. The rest of the base is added in increments.

The fusion method is used when the base contains solids that have higher melting points (e.g., waxes, cetyl alcohol, glyceryl monostearate). This method is also useful for solid medicaments, which are readily soluble in the melted base. The oil phase should be melted separately, starting with materials that have the highest melting point. All other oil–soluble materials are added in decreasing order of melting points. The ingredients in the water phase are combined and heated separately to a temperature that is equal to or several degrees above that of the melted oil phase. The two phases are combined. If a w/o system is desired, then the hot aqueous phase is incorporated into the hot oil phase with agitation. If an o/w system is desired, then the hot oil phase is incorporated into the hot aqueous phase. Volatile materials (e.g., menthol, camphor, iodine, alcohol, perfumes) are added after the melted mixture has cooled to 40 °C or below.

In packaging ointments and ointment–type products, such factors as ease of application, cleanliness, sterility, stability and minimization of microbial contamination should be taken into account. Traditionally, onitments are packaged in wide–mouthed jars made of glass, porcelain, or plastic, or in metal or plastic tubes. Whenever possible, the use of aerosol containers is preferable. The advantages of aerosol products include the convenience of push–button dispensing of medication and the stability afforded by a closed, pressurized container that minimizes the likelihood of tampering and protects the contents from light, moisture, air (oxygen), and microbial contamination. The ointment is dispensed as а spray, a foam, or a magma.

II.5. Ответьте на вопросы по содержанию текста А.

1. What are ointments intended for?

2. What is the difference between the two main types of ointments?

3. Which of the three types of ointments (endodermic, epidermic or diadermic) has the highest potential for penetration through the skin?

4. What are the two methods of preparation of ointments?

5. When is the fusion method used?

6. How are the volatile ingredients (e.g., camphor) added to the ointment in the process of fusion?

7. How are ointments traditionally packaged in pharmacies? in pharmaceutical plants?

8. What are the advantages of aerosol containers over other types of containers?

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II.7. Прочтите и переведите текст В.

II.8. Подчеркните все союзы и предлоги в тексте В. Переведите предложения, в которых вы их встретили в тексте.

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