Topical Applications

A topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.

Many topical medications are applied directly to the skin.  Topical medications may also be inhalational, such as asthma medications, or applied to the surface of tissues other than the skin, such as eye drops applied to the conjunctiva, or ear drops placed in the ear, or medications applied to the surface of a tooth.  As a route of administration, topical medications are contrasted with enteral (in the digestive tract) and parenteral administration (injected into the circulatory system).

The effect may be local or systemic.  Some hydrophobic chemicals, such as steroid hormones, can be absorbed into the body after being applied to the skin in the form of a cream, gel or lotion.  Transdermal patches have become a popular means of administering some drugs for birth control, hormone replacement therapy, and prevention of motion sickness.

Function

There are many types of topical application, with no clear dividing line between similar formulations.  As a result, what the manufacturer's marketing department chooses to list on the label of a topical medication might be completely different than what the form would normally be called.  For example, Eucerin "cream" is more appropriately described as an ointment than as a cream.

Solution
Generally a liquid consisting of a powder dissolved in a base of water, alcohol or oil.  Tends to be drying if high alcohol content.  Moderate irritation risk depending on base.  Significant sensitization risk depending on preservative and fragrances.  Avoid in fissures and erosions.  High rate of acceptance due to ease of application and cosmetic feel.

Lotion
Similar to solution but thicker and tends to be more soothing and moisturizing.  Tends to be oil in water, and tends to have less alcohol than solutions.  Can be drying if contains excessive alcohol.

Shake Lotion
A mixture that separates into two or three parts with time.  Frequently an oil mixed with a water-based solution.  Needs to be shaken into suspension before use.

Cream
Cream is thicker than lotion, and maintains its shape when removed from its container.  It tends to be moderate in moisturizing tendency.  For topical steroid products, oil-in-water emulsions are common.  Creams have a significant risk for causing immunological sensitization due to preservatives.  It has a high rate of acceptance by patients.

Ointment
An ointment is a homogeneous, viscous, semi-solid preparation, most commonly a greasy, thick oil with a high viscosity, that is intended for external application to the skin or mucous membranes.  They are used as emollients or for the application of active ingredients to the skin for protective, therapeutic, or prophylactic purposes and where a degree of occlusion is desired.

Ointments are used topically on a variety of body surfaces.  These include the skin and the mucous membranes of the eye (an eye ointment), vagina, anus, and nose.  An ointment may or may not be medicated.

Ointments are usually very moisturizing, and good for dry skin.  They have a low risk of sensitization due to having few ingredients beyond the base oil or fat, and low irritation risk.  They are often disliked by patients due to greasiness.

Gel
Thicker than a solution.  Often a semisolid emulsion in an alcohol base.  Some will melt at body temperature.  Tends to be cellulose cut with alcohol or acetone.  Tends to be drying.  Significant risk of inducing hypersensitivity due to fragrances and preservatives.  Useful for the scalp and body folds.  Avoid fissures and erosions due to drying and stinging effect of alcohol base.

Foam
Can be seen with topical steroid marketed for the scalp.

Transdermal Patch
Can be a very precise time release method of delivering a drug.  Cutting a patch might cause rapid dehydration of the base of the medicine, and affect the rate of diffusion.

Powder
Either the pure drug by itself (talcum powder), or mixed in a carrier such as corn starch or corn cob powder.  Can be used as an inhaled topical (cocaine powder used in nasal surgery).

Solid
Medication placed in a solid form.  Such as deodorant, antiperspirants, astringents, and hemostatic agents.  Some solids melt when they reach body temperature (e.g. rectal suppositories).

Sponge
Certain contraceptive methods relies on the sponge as a carrier of a liquid medicine.  Lemon juice embedded in a sponge has been used as a primitive contraception in some cultures.

Tape
Cordran tape is an example of a topical steroid applied under occlusion by tape.  This greatly increases the potency and absorption of the topical steroid and is used to treat inflammatory skin diseases.

Vapor
Some medications are applied as an ointment or gel, and reach the mucous membrane via vaporization.  Examples are nasal topical decongestants and smelling salt.