Different skin surfaces respond differently to topical corticosteroid therapy; this different response rate varies relative to the absorption of the steroid into the deeper tissues. The relatively thin skin surfaces of the face respond very rapidly to the use of group VII agents, whereas the thicker skin of the palms and soles requires a highly potent steroid. Issues that result in an effective higher potency application when using a low-potency agent include: raw, inflamed skin (such skin more rapidly and readily absorbs medication); treatment regions involving skin surfaces in frequent contact, such as intertriginous areas (the apposition of two skin surfaces produces enhanced absorption of drug similar to the effect to an occlusive dressing); and areas of skin surfaces enclosed under tight clothing, such as the diaper area (once again, enhanced absorption of the agent due to the occlusive effect of the garment). In general, lower potency agents are acceptable in these situations.
The application of creams, ointments, gels, and lotions is relatively straightforward. The medication, applied in thin layers, should be massaged into the skin as directed daily. Prewashing the skin prior to corticosteroid application is unnecessary. Patients should be advised to follow directions closely, both early and late in the treatment course. Early application with either extra medication per dose or more frequent medication administrations is not desired; likewise, both a reduced frequency of application or a decreased amount of medication as the disease process responds to therapy can cause relapse. Optimum application regimens have not been determined for topical corticosteroids in most dermatologic syndromes. The more potent agents are best applied two to three times daily for 1 to 2 weeks followed by a drug-free week; additional therapy may be required as determined by the disease as well as by the particular patient's response to the initial therapy. Agents from the less potent steroid groups may be applied three times daily for 2 to 4 weeks followed by a seven day steroid-free period.
The prescription of the correct amount of topical steroid is at times difficult. The burn rule of nines may be used to estimate the amount of topical corticosteroid to prescribe. Calculate the percentage of body surface area requiring therapy; then, multiply the percentage by a correction factor of 30. This calculation will provide the amount of topical corticosteroid in grams for a single application. Next, determine the number of administration required in the treatment course. For example, a tid regimen for a duration of 10 days ultimately requires 30 applications. The number of applications is multiplied by the amount required for a single use. In general, 9 g of topical steroid will cover 9 percent of the body surface area in a tid application for a single day.
Tachyphylaxis refers to the decrease in responsiveness to a drug as a result of enzyme-mediated events. The term is used in relation to topical corticosteroids in reference to acute tolerance to the vasoconstricting ability. In general, vasoconstriction has been demonstrated to decrease progressively over time when a topical steroid is applied. Such reductions in strength due to tolerance are encountered as early as four days into the treatment course in all potency groups yet are felt to be more important in groups I and II. A reasonable strategy to employ to counter the development of tachyphylaxis is the use of interrupted application schedules; such an interrupted treatment course might include an initial tid application for two weeks followed by a single week of drug holiday followed by a repeat of the cycle.
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