Chapter 4. Topical Corticosteroids
For approximately 50 years, topical corticosteroids have been the primary prescribed therapy for atopic dermatitis. Topical steroids are effective for both acute and chronic disease. By acting on multiple resident and infiltrating cells, they are effective in reducing inflammation and pruritus. In addition, topical corticosteroids reduces S. aureus skin colonization by reducing skin inflammation.
Topical corticosteroids are formulated in potencies ranging from extremely high strength (class 1) to low "over the counter" strength (class 7). The vasoconstrictor assay, which measures the ability of a steroid to produce blanching when applied to normal human skin under controlled conditions, remains the gold standard for determining the potency of a topical corticosteroid.
Of note, the vehicle can alter the potency of the corticosteroid, making it more or less potent. Topical corticosteroids are available in a number of different bases that include ointments, creams, lotions, solutions, gels, sprays, foam, oil and steroid-impregnated tape. Because of this, there is generally no need to compound these medications. Ointment-based preparations are most occlusive, have the fewest additives, and decrease evaporative losses. However, cream formulations may be better tolerated in excessive heat or humidity, and may preferred by some for the decrease in "greasiness" as compared to ointments. In general, however, while creams and lotions are easier to apply, they may contribute to skin irritation and xerosis in some patients. Solutions and foams are useful for eczema of the scalp or other hirsute areas, although the alcohol in them can be irritating when used on inflamed or excoriated skin. While generic formulations are required to have the same active ingredients and concentration as the original product, many do not have the same formulation of the vehicle and bioequivalence can vary significantly.
Adverse effects reported with topical corticosteroid therapy include local effects such as skin atrophy, striae, telangiectasia, perioral dermatitis, and acneform eruptions as well as less frequent systemic effects such as hypothalamic-pituitary-adrenal axis suppression and cataracts. Most adverse effects are associated with use of potent topical steroids, although chronic use of less potent steroid preparations, especially on the face, groin or axillae can lead to local side effects. Ingredients in topical steroid bases and rarely the corticosteroid molecule itself can cause an allergic contact dermatitis. The latter may be difficult to recognize in a patient with chronic atopic dermatitis since it can present as acute or chronic eczema.
Prescribing the optimal topical corticosteroid will depend in part on the severity of the atopic dermatitis and distribution of lesions. Caregivers need to be informed about the potency and potential side effects of the topical corticosteroid preparation prescribed. As discussed in the section on Education, caregivers or patients may mistakenly assume that the potency of a topical corticosteroid is defined by the percent stated after the compound name, rather than by the specific compound. Prescribing “the least potent corticosteroid that is effective” is a general rule, though this needs to be balanced by the possibility that utilizing too weak a topical corticosteroid may result in persistence or worsening of atopic dermatitis. For moderate to serve atopic dermatitis, a step-care approach can be used starting with a mid or high potency preparation to eczema other than on the face, groin or axillae, then tapering to a lower potency preparation with clinical improvement. Use of high potency topical corticosteroids should be used cautiously, preferably under the care of a specialist and be reserved primarily for severe eczema of the hands or feet. It is important to know that Lotrisone in addition to an antifungal contains a high potency corticosteroid and should rarely be used for treating atopic dermatitis and never applied to the face, groin or axillary regions.
Adequate amounts of topical corticosteroids should be prescribed, especially to patients with widespread disease. It has been estimated that approximately 30 grams of medication are needed to cover the entire body of an average sized adult once. In children with atopic dermatitis, the finger-tip unit (FTU), defined as the amount of topical medication extending from the tip to the first joint on the palmar aspect of the index finger has been suggested as a measure for applying topical corticosteroids. It takes approximately one FTU to cover the hand or groin, 2 FTUs for the face or foot, 3 FTUs for an arm, 6 FTUs for the leg, and 14 FTUs for the trunk. Caregivers who have to refill prescriptions frequently may undertreat a patient’s eczema and in addition, obtaining medications in larger quantities can result in significant savings for patients
Topical corticosteroids have typically been applied twice daily and using them more frequently may increase side effects and cost without significant clinical benefit. On the other hand, once daily treatment has been shown to be effective for certain corticosteroid preparations, including fluticasone propionate and mometasone furoate and could improve adherence with the treatment regimen.
While topical corticosteroids have not been considered appropriate for “maintenance therapy” in atopic dermatitis especially on normal-appearing skin, several recent studies with fluticasone propionate in patients as young as 3 months of age have shown that once the disease is stabilized, long-term control can be maintained with twice weekly therapy. In these studies, the maintenance corticosteroid preparation was applied to areas that appeared to have healed, which resulted in delayed relapses compared with placebo therapy. Newer approaches incorporate topical steroids as "rescue" therapy in conjunction with non-steroidal medications.
There are a number of reasons that patients with atopic dermatitis may not respond appropriately to their prescribed topical corticosteroid therapy. These include inadequate potency of the preparation or insufficient amount dispensed as discussed above. In addition, S. aureus superinfection, contact allergy to the steroid molecule and possibly corticosteroid insensitivity. However, a much more practical reason for therapeutic failure with topical corticosteroids is non-adherence with the treatment regimen. As with any chronic disease, caregivers or patients often expect a quick and permanent resolution of their illness. In addition, a significant number of caregivers admit to non-adherence with use of prescribed topical corticosteroids due to fear of adverse effects.