Topical

Topical

In the realm of medicine, a topical medication is administered to body surfaces such as the skin or mucous membranes found in areas like the vagina, anus, throat, eyes, and ears.

Numerous topical medications are applied directly onto the skin, known as epicutaneous administration. Alternatively, they can be inhalational, as seen with asthma medications, or applied to tissues other than the skin's surface, such as eye drops for the conjunctiva, ear drops for the ear canal, or medications for tooth surfaces. Topical administration differs from enteral (through the digestive tract) and parenteral administration (injection into the circulatory system).

Regarding pharmacodynamics, a topical effect typically targets a local area rather than affecting the entire system. Nevertheless, many topically administered drugs can have systemic effects.

Certain hydrophobic substances, like steroid hormones, can be absorbed into the body after application to the skin in the form of creams, gels, or lotions. Transdermal patches are increasingly used for delivering drugs related to birth control, hormone replacement therapy, and motion sickness prevention. An example of a topical antibiotic is chloramphenicol.

The potency of a medication often varies with its base. For instance, some topical steroids are classified as stronger when transitioning from cream to ointment. Generally, ointment bases are more occlusive and facilitate quicker absorption into the skin compared to solution or cream bases.

The manufacturer of each topical product has full control over the medication's base content. Even though two creams may contain the same active ingredients, one might be more acidic than the other, potentially leading to skin irritation or altering absorption rates. For example, a vaginal miconazole antifungal cream may cause less skin irritation than one designed for athlete's foot. These differences can sometimes yield varying clinical outcomes, despite the identical active ingredient.

Comparative potency labeling is absent to ensure equal efficacy between generic and brand-name topical steroids. Studies have shown variations in potency among different manufacturers or brands. For instance, clinical studies have revealed that brand-name Valisone cream and Kenalog cream exhibit significantly better vasoconstriction than certain generic versions of the same drug. However, in a simple base like an ointment, less variation between manufacturers is typical.

In dermatology, the base of a topical medication is often as crucial as the medication itself. It is essential to receive the medication in the correct base before application to the skin. A pharmacist should avoid substituting an ointment for a cream, or vice versa, as it can alter the medication's potency. Some physicians prefer using a thick ointment to restore the waterproof barrier of inflamed skin in treating eczema, as a cream might not achieve the same therapeutic outcome.