Topical Corticosteroids: Focus on Appropriate Potency and Vehicle

The human skin is frequently represented as a basic three-layered structure, but it is actually a complex series of diffusion barriers.¹ Dermatologic therapy requires the flux of drugs and drug vehicles through these barriers.¹ The pharmacologic response to medications topically applied to the skin is determined by several variables, including (1) the potency of the product itself; (2) the skin region to which the product is applied (eg, face vs forearm), which affects drug penetration; (3) the vehicle (eg, cream, ointment, lotion) into which the therapeutic ingredients are incorporated and diluted; (4) use or lack of use of an occlusive dressing to increase a drug’s contact with skin; (5) the dosing schedule; and (6) the duration of treatment.¹ Presence or absence of these variables is part of the reason that topical corticosteroids are available in such a broad variety of products, particularly with respect to potency and vehicle. Because of their anti-inflammatory properties, topical corticosteroids are the mainstay of treatment for most noninfectious inflammatory dermatoses.² This column includes key concepts for NPs prescribing these agents (so as to streamline the product selection process) and provides tips for facilitating successful treatment and reducing the risk for unwanted side effects (Sidebar).^2-5 Discussing pharmacologic management of specific dermatologic conditions is beyond the scope of this article. NPs are directed to online reference 6 for an overview of dermatologic disorders that includes a discussion of the approach to dermatologic problems and descriptions of specific skin lesions.

According to Ference et al,³ successful treatment with topical corticosteroids depends on several factors, starting with an accurate diagnosis. Conditions for which topical steroids are commonly used are listed in Table 1 (see sidebar),^3,4,7 which also includes links to online photos to illustrate these conditions. Although topical steroids are commonly prescribed, evidence of their effectiveness is available only for conditions such as psoriasis, atopic dermatitis, eczema, vitiligo, phimosis, acute radiation dermatitis, and lichen sclerosus.³ Evidence of these agents’ effectiveness in chronic idiopathic urticaria, alopecia areata, and melasma is limited.³ Relative contraindications for use of topical corticosteroids include acneiform conditions and conditions in which there is an underlying infectious process.² However, in select patients with highly inflammatory acne, topical steroids can be applied for short periods of time.⁸ These agents may help reduce flare-ups in severe conglobate acne and may help reduce granuloma pyogenicum-like lesions in patients receiving systemic isotretinoin therapy.⁹ When the diagnosis is unclear, referral to a dermatologist is recommended.³ Referral is also recommended when standard treatments fail or when allergy patch testing is not available.

Regional variation in medication penetration is an important concept to consider when choosing the potency of a topical corticosteroid for a patient’s dermatologic condition. Of note, less medication may be required on the considerably more permeable face, axilla, scalp, and scrotum, as compared with the forearm.¹ A lower potency and shorter course of topical steroid therapy are usually required in children.³ Although the terms used to categorize potency may vary from reference to reference, topical corticosteroids are generally described as ranging from low- to super/ultra-high potency (see sidebar for Table 2).

Potency depends on many factors, including a drug’s characteristics (eg, fluorination or chlorination/halogenation of the drug compound) and concentration, and the base in which the drug is used.² Table 1 outlines select conditions commonly treated by agents under potency categories. In general, high-potency and super-high-potency topical corticosteroids are not used on the face, groin, or axilla, or with an occlusive dressing (see section on Dressings) except in rare cases and for short courses of therapy.³ Low-potency agents are the safest choice for use on the face or areas of the body with thinner skin, for application over large areas of the body, for long-term use, and for use in children.3

Table 2 lists topical corticosteroids based not only on potency but also on the various vehicles that deliver the drug and render it effective. Although a vehicle influences a drug’s effectiveness, the vehicle itself may cause adverse effects such as contact or irritant dermatitis. Therefore, careful consideration goes into selecting the appropriate vehicle for delivery of the topical steroid.² In general, aqueous preparations are used to treat acute inflammatory conditions because of their drying effect (the liquid evaporates), whereas oil-based formulations are selected for chronic inflammatory conditions because of their moisturizing property.² General usefulness of the available vehicles is described here.^2-5 Creams are semi-solid emulsions of oil and water that vanish when rubbed into the skin. Creams are used on the face and intertriginous areas, usually for management of inflammatory dermatoses. When exudation is present, creams are moisturizing and cooling. Some patients prefer creams over other vehicles for cosmetic reasons. Ointments such as petrolatum are oil based, with little if any water. They are used on dry scaly areas as optimal lubricants. Because ointments increase drug penetration as a result of their occlusive action, they are selected when increased potency is required; that is, the concentration of active ingredient is generally higher in an ointment than in other vehicles. Ointments are chosen for treating lichenified lesions, crusted lesions, and mounded scales, as seen in psoriasis and lichen simplex chronicus. Ointments are less irritating than creams for erosions or ulcers. Solutions are convenient to apply, especially for management of psoriasis or seborrhea of the scalp. These vehicles tend to be drying. Lotions are water-based emulsions that are easy to apply to hairy skin. They are selected for use on intertriginous areas and the face. Lotions provide a cooling and drying action useful for acute inflammatory and exudative lesions such as contact dermatitis, tinea pedis, and tinea cruris. Gels contain ingredients suspended in a solvent thickened with polymers. Gels can be beneficial for oily or hairy areas. They are used to manage acne, contact dermatitis, rosacea, and psoriasis of the scalp. Tape, impregnated with corticosteroid, may be selected to protect an area from excoriation. This vehicle provides increased drug absorption and, therefore, increased potency. Of note, the contents of foam formulations (eg, petroleum-based emulsion aerosol products) may contain alcohol and propane/butane, which are flammable.¹⁰ Patients using these products must avoid fire, flame, and/or smoking during and immediately following application.

Dressings are used not only to protect an open lesion, facilitate healing, and protect a patient’s clothing, but also to increase absorption of drug.² Nonocclusive dressings such as gauze allow air to come in contact with the lesion and may be used with saline (ie, wet to dry dressings) to help cleanse and debride a thick or crusted lesion.^2,11 Occlusive dressings are used to increase absorption and effectiveness of topical steroid therapy. The most common form of an occlusive dressing is a transparent film (eg, polyethylene [household plastic wrap]) or flexible, transparent, semi-permeable dressings.2 Occlusive dressings are recommended for treating conditions such as atopic dermatitis, psoriasis, chronic hand dermatitis, and the skin lesions of lupus erythematosus. However, use of occlusive dressings with topical steroids can be associated with skin atrophy, bacterial or fungal infections, striae, and miliaria, among other risks (Table 3).^2-4,7

Topical corticosteroids are usually applied 2-3 times daily; once-daily or less frequent dosing may be required with high-potency agents.² In many dermatologic conditions, once-daily application of a topical steroid appears to be just as effective as multiple applications.¹ This phenomenon is due to the fact that the skin acts as a reservoir for some drugs, resulting in a local half-life that may be considerably longer than the systemic half-life, thereby enabling once-a-day dosing.¹ According to Ference et al,³ the optimal dosing schedule is determined by trial and error, but most topical corticosteroid preparations are applied once or twice daily.

Tolerance and tachyphylaxis (rapidly decreasing response after administration of a few doses) may result from chronic application of topical corticosteroids.³ Ference et al³ have indicated that ultra-high-potency steroids should not be used for longer than 3 weeks continuously. If a longer duration is required, the steroid is gradually tapered to avoid rebound symptoms. Treatment may be resumed after a steroid-free period of ≥1 week.³ Pediatric patients frequently require a shorter duration of treatment, as well as a lower-potency steroid. To avoid adverse effects, continuous use of low-potency to high-potency topical steroids should not exceed 3 months. Contact dermatitis in reaction to preservatives and additives in topical steroid formulations is common with prolonged use.² Furthermore, contact dermatitis related to the corticosteroid itself may occur.

Table 3 lists potential adverse effects of topical corticosteroids. All such agents can cause skin atrophy, striae, and acneiform eruptions when used for >1 month.² Skin atrophy may present as depressed, shiny, frequently wrinkled skin with prominent telangiectases; a tendency to develop purpura and ecchymosis may ensue.¹ Topical steroids may increase the risk for infections such as exacerbation of cutaneous infection, masked infection, and secondary infection (eg, promotion of fungal growth).^3,12 To lower the risk for tinea infections, combination products containing a topical steroid and antifungal agent are best avoided.³ Contact dermatitis occurring in reaction to preservatives, additives, or the corticosteroid itself may occur with prolonged use. All absorbable topical corticosteroids can cause hypothalamic–pituitary–adrenal (HPA) axis suppression.¹ Risk for systemic side effects is higher when these agents are used in children, applied over extensive skin surfaces, and/or used for a long duration (with or without occlusion).¹ Other systemic side effects caused by topical application of high- and super-high potency corticosteroids include glaucoma, hyperglycemia, hypertension, and septic necrosis of the femoral head.³ Patients must be counseled that photosensitization can occur with use of topical corticosteroids. Patients on long-term topical steroids are advised to avoid abrupt cessation of use.⁴

The safety of topical corticosteroids in pregnant women who may require these agents to treat dermatologic conditions is unclear. A Cochrane review showed that few data are available regarding any relationship between prenatal use of topical steroids and preterm delivery, stillbirth, or birth defects.13 Using large quantities of very potent topical steroids has been related to low birth weight, however.