Most common skin disorders can be treated with a formulary of cost-effective, widely available topical and oral products. Topical medications are effective for most common skin disorders and they have fewer serious adverse side effects when compared with their oral counterparts. Oral medications may be needed if a skin disease is widespread or more severe.

There are several things to consider before prescribing a topical product such as the active ingredient, the vehicle, and the quantity to dispense.

The vehicle of a topical product may be as important as the active ingredient. Table 6-1 lists commonly used vehicles. “If it’s dry, wet it and if it is wet, dry it” is still a good general guideline for treatment of common dermatoses. Most skin disorders, especially the chronic dermatoses (eg, psoriasis, chronic contact dermatitis), are “dry”; therefore, ointments are preferred as they are more moisturizing. Also, ointments do not contain preservatives that can cause stinging and burning. The main problem with ointments, is that they are greasy and can stain clothing and bedding. Creams are a good option for the “wet” dermatoses, such as acute contact dermatitis, and other blistering or exudative dermatoses. They are also a good option for adults who do not want to use an ointment. However, some cream preparations are slightly drying and preservatives and other ingredients in the vehicle may sting or burn.

The quantity of medication to be dispensed and the amount of medication that is needed per application are important considerations in prescription medications, especially topical steroids and calcineurin inhibitors.

There are a few general rules that can be used to estimate the quantity of topical medication a patient will need; however, the required amount may vary a great deal depending on the age of the patient, body size, type of vehicle, and how thickly the product is applied. In general:

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  Approximately 30 g of cream will cover the entire adult body for 1 application.

  
  
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  As an approximation, infants will need one fifth of the adult quantity, children two fifths of the adult quantity, and adolescents two thirds of the adult quantity.¹

It is also important to give instructions to patients on what quantity of medication they need to apply per application. The fingertip unit (FTU) is a commonly used measurement.² A FTU is the amount of medication dispensed (squeezed) from a tube with a 5 mm nozzle that covers the skin of the index finger from the tip to the distal crease (Figure 6-1). One FTU is equal to approximately 0.5 g. One FTU will cover an area of skin equivalent to the area covered by 2 hands. Another option for estimating larger quantities is the use of a standardized kitchen tablespoon. One tablespoon holds slightly less than 15 g of a cream or ointment which will cover approximately half of an adult body.

Topical medications are usually packaged in increments of 15 g, most commonly in tubes and bottle sizes of 15, 30, 45, and 60 g. Many generic topical steroid medications can be dispensed in jars of larger sizes, typically at a lower cost per gram.

The cost of medications is an increasingly important issue and may affect a patient’s decisions about the purchase and use of a prescription medication. There are generic forms of most of the commonly used topical medications. A study published in 2012 reported that in the United States, the average generic dermatologic medication was $55.84 compared with $115.72 for brand name products resulting in a cost saving of almost 55%.³

There were concerns about the quality of topical generic medications several years ago, but recent studies on selected products have shown that they are equivalent in efficacy to brand name medications.³ There are, however, some products such as emollient steroid creams, augmented steroids, combination medications, and certain vehicle preparations that are available only as branded products.

Topical steroids are used for a wide range of inflammatory skin disorders such as dermatitis and papulosquamous skin disorders. They have anti-inflammatory, antiproliferative, and immunosuppressive effects on the skin. In the United States topical steroids are ranked from class 1 to 7 with superpotent steroids in class 1 and the least potent steroids in class 7.⁴ The steroids in any one class have equivalent potency, so a limited formulary of topical steroids is sufficient in most cases (Table 6-2).

There are many factors to consider when prescribing a topical steroid including the nature of the disease to be treated, the location of the rash, the amount of steroid needed, duration and frequency of treatment, and the age of the patient (Table 6-3).⁵

The risks of topical steroids are less severe than those associated with the use of oral corticosteroids; however, in certain situations the topical adverse effects can be cosmetically distressing to the patient and damaging to the skin (Table 6-4).⁶ Systemic adverse reactions, similar to those seen with systemic steroids, can occur with the use of more potent topical steroids, especially in children.