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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5577_Библиотеки_им_академика_М_И_Перельмана.pdf
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Manufacture and Supply, Science and Reg ulation Towards High-Qua lity Medicinal Products
A number of pharmaceutical and cosmetic products are formulated as emulsions. They may be administered topically, orally and
parenterally.
Examples of pharmaceutical emulsions
Pharmaceutical Dosage Forms
The choice of materials for the oil phase is determined primarily by
the ultimate use of the emulsion. A wide variety of lipids or lipophilic materials such as mineral oils, vegetable oils, silicones and
waxes may be used to form the oil phase.
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Dierent types of oils used in making emulsions
Emulsifying agents are customarily divided into three broad
classes, namely, surfactants, hydrophilic colloids and finely divided
solids. The factors aecting the selection of emulsifying agents
include the types of emulsion, i.e., whether the oil is dispersed in
the water (O/W emulsion) or whether the water is dispersed in the
oil (W/O emulsion), compatibility of the emulsifying agent with
other components of the emulsion, toxicity of the emulsifying
agent, and its cost.
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Manufacture and Supply, Science and Reg ulation Towards High-Qua lity Medicinal Products
Dierent types of emulsifying agents used in making emulsions
Depending on the purpose of the emulsion, antimicrobial preservatives, antioxidants or chelating agents, buers, colors, sweetening
agents, flavors and fragrances may be added in the formulation of an
emulsion. In particular, antioxidants are added to prevent degradation of the emulsified oils upon exposure to air (oxygen). Unsaturated
oils, such as vegetable oils, may give rise to rancidity with resulting
unpleasant odor and taste. Examples of antioxidants include butylated
hydroxytoluene, butylated hydroxyanisole, L-tocopherol and alkyl
gallates. If traces of metallic ions, which are likely to catalyze oxidative degradation, are present in the emulsion, chelating agents such
as citric acid, maleic acid and phosphoric acid may be added.
In the manufacture of pharmaceutical emulsions, dierent types
of emulsifying machines have been employed to produce emulsions
by simple stirring, colloid milling, vibration or ultra-sonification.
Pharmaceutical Dosage Forms
The oil phase and aqueous phase are prepared separately and subsequently combined in the emulsifying machine. In the absence of
thermosensitive components, heat may be employed to facilitate
the emulsification process.
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A physically stable emulsion is one in which there is no coalescence
of the disperse phase that ultimately leads to separation of the oil
and the water phases. As soon as an emulsion has been prepared,
time- and temperature-dependent processes occur to eect separation of the two immiscible phases (oil and water). Emulsion instability is shown by creaming, flocculation, coalescence and eventual
cracking. When cracking happens, there is a complete breakdown of
the emulsion, with coalescence of the droplets and a separation of
the two phases into two layers. This process is irreversible. Cracking
may result from chemical, physical and biological eects.
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Manufacture and Supply, Science and Reg ulation Towards High-Qua lity Medicinal Products
14.5.6. Creams
A cream is a semi-solid dosage form consisting of an emulsion base.
Creams are divided into two types: O/W creams which are composed of small droplets of oil dispersed in a continuous water phase,
and W/O creams which are composed of small droplets of water dispersed in a continuous oil phase. Additives with thickening eects
are added to the continuous phase to increase the viscosity of the
preparation. O/W creams are generally more acceptable as they are
less greasy and more easily washed o using water. However, W/O
creams are more moisturizing as they provide an oily barrier which
reduces water loss from the stratum corneum, the outermost layer
of the skin. The type of cream used as a base for the drug depends
on the application and desired outcome. For example, a W/O cream
is not suitable as a base for a drug used to treat acne as its greasiness
will clog the skin pores and aggravate acne.
Skin anatomy
Pharmaceutical Dosage Forms
You may have come across the terms cold cream and vanishing
cream, especially in cosmetic products. A cold cream is a W/O cream
that is traditionally produced using beeswax and borax. These two
components will interact chemically to form an emulgent to stabilize the cream. Cold creams are so called as they are often used
during colder weather conditions because of their higher oil content
and ability to prevent dry skin. Cold creams are also mainly used
for skin treatment such as facial mask or lip balm due to their moisturizing properties. They can also be formulated to smoothen skin,
remove makeup and to be used as shaving creams.
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A vanishing cream is an O/W cream that seems to disappear or vanish
when spread on the skin, which explains its name. Like cold creams,
vanishing creams also keep the skin moisturized but to a smaller
extent. As it has a lower oil content, it does not clog the skin pores as
much as a cold cream, while providing the skin with a matte finish.
As creams are basically composed of an emulsion base, they are
manufactured in the same way as an emulsion. Heat is commonly
employed in the manufacture, where the liquid congeals to form
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Manufacture and Supply, Science and Reg ulation Towards High-Qua lity Medicinal Products
Oxy 10 — An example of a vanishing cream
the cream (semi-solid) upon cooling. Unlike liquid pharmaceutical
emulsions which are usually packed into glass bottles, creams are
often filled and packed into plastic or aluminum tubes of 5 g, 10 g or
15 g capacity with the batch numbers and expiry dates embossed at
the base of these tubes after they have been machine-sealed by the
process of crimping.
14.5.7. Ointments
An ointment commonly refers to a semi-solid dosage form with an
oleaginous base that is composed entirely of lipophilic materials
(fats and oils). Examples of these lipophilic materials include:
Pharmaceutical Dosage Forms
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• Hydrocarbons — e.g., petrolatum, paran wax, liquid paran,
microcrystalline wax and ceresin.
• Vegetable oils — e.g., peanut oil, almond oil, sesame oil, olive oil
and coconut oil.
• Hydrogenated oils — e.g., hydrogenated cotton seed, soya bean,
corn and castor oils.
• Silicones — e.g., dimethylpolysiloxanes, methylphenylpolysiloxanes and stearyl esters of dimethylpolysiloxanes.
• Acids, alcohols and esters — e.g., stearic acid, oleic acid, palmitic
acid, stearyl alcohol, cetyl alcohol, lauryl alcohol, glyceryl tristearate and isopropyl myristate.
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Manufacture and Supply, Science and Reg ulation Towards High-Qua lity Medicinal Products
Petrolatum, also known as petroleum jelly, is one of the most popular oleaginous bases used in making ointments. Petrolatum is tasteless, odorless and is an excellent emollient. It is also compatible with
many drugs and it provides optimal drug stability to the ointment
product such as analgesic and anti-inflammatory balms, and antibiotic ointments.
Products composed of oleaginous bases
Antibiotic ointments for treatment of eye infections
Pharmaceutical Dosage Forms
Ointments are prepared by two general methods, namely the “Incorporation Method” and the “Fusion Method”. The method employed
for preparation depends on the nature of the ointment components.
Under the Incorporation Method, no heating is employed. The base is
prepared by blending its components. It is then mixed with the drug
to obtain a homogeneous product. An advantage of this method is
its suitability for thermolabile drugs. However, the Incorporation
Method is more suitable for small-scale production that usually
employs the mortar and pestle, or the ointment slab and spatula.
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Can you recognize any of these semi-solid pharmaceutical products? Which products are creams and which ones are ointments?