Topical Treatments

Most drugs used in dermatology are topical: they are applied to the skin surface in the form of ointments, creams, lotions, gels, and powders.

Topical drugs have advantages over systemic drugs. They deliver the medication directly to the organ that needs treatment - sometimes called the target organ - the skin. Topicals are also less likely to provoke systemic side effects than systemic drugs are.

A topical drug cannot be effective if it does not penetrate the skin’s outer protective layer and deliver its healing medication. Penetration through the skin is affected by the condition of the skin itself and the physical and chemical properties of the two parts of a topical dermatologic drug: the active and the vehicle.

The active, or active ingredient, is the therapeutic drug substance itself. The vehicle, sometimes called the base, is the medium in which the active is formulated.

The vehicle is an important part of an effective drug. An unsuitable vehicle will diminish a drug’s therapeutic effects, but a suitable base can optimize a drug’s efficacy.

The common dermatologic vehicles:

Creams
Creams are semisolid emulsions of oil in water. An emulsion is a suspension of tiny globules of one liquid in a second liquid with which the first will not mix. Oil and vinegar salad dressing is an everyday example of an emulsion.

Creams are usually soft, white, and non-greasy, and they vanish when rubbed into the skin. The ratio of oil to water in creams varies. In general, the more oil in the emulsion the more ointment-like the cream will be.

Creams are versatile vehicles that are useful in a wide range of skin diseases. They are easy to rub in and do not feel tacky or greasy.

Ointments
Ointments are semisolid emulsions of water droplets suspended in oil. Because ointments are lubricating, they are often used to treat dry, scaling lesions with thickened skin.

Ointments are more occlusive than creams are - they form a film on the skin that creates a greenhouse effect which increases the skin’s temperature and water content. This effect makes it easier for the topically applied substance to penetrate the skin’s outer protective layer.

Lotions
Lotions are either suspensions of insoluble powder in a liquid or pourable emulsions of oil in water. Pourable emulsions are often called creamy lotions. Lotions generally have a cooling effect, and they are often recommended for hairy areas. They tend to wear off more easily than creams or ointments, and they can be drying.

Solutions
Solutions are liquid preparations that contain soluble chemical substances dissolved in water or alcohol. Alcoholic solutions are sometimes called tinctures. Solutions, like lotions, have a cooling effect but they may be too drying.

Aerosols
Aerosols may be solutions or lotions delivered by a propellant. Aerosols are cooling and are recommended when touching the skin would be painful.

Gels
Gels are semisolid emulsions that liquefy when applied to the skin. When gels contain alcohol, they may burn or irritate inflamed skin.

Powders
Powders are dry granular particles that may contain active ingredients such as antibiotics or antifungals. Powders are cooling and drying, and are often used to treat wet lesions.

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