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Fig 2.17 Topical Steroids

Four potency groups

Use proprietary names

Potency unaltered by dilution

Ointments medically preferable to creams

this is not the case. Such dilution serves only to reduce the dose of steroid per unit volume of any given preparation. However, use of a cream or ointment vehicle may be relevant regarding potency, as ointments provide a semiocclusive effect that can increase potency. Furthermore the bio-availability of the topical steroid can be enhanced by certain additional constituents, e.g. propylene glycol, and keratolytic agents like salicylic acid and urea. Hydrocortisone acetate 1% moves from the 'mildly potent' group of topical steroids to the group termed 'moderately potent' with the addition of urea to the preparation. The cream and ointment vehicles used to deliver steroids to the skin have similarities to those used as emollients, but additional constituents are required to dissolve the otherwise insoluble steroid molecule. Although one well known topical steroid vehicle is also available as a separate emollient, vehicles are not generally available separately. While a patient's preference for a cream needs to be acknowledged to ensure optimal compliance, the potentially sensitising additives in creams sometimes make ointments medically preferable (Fig 2.17).

n o m z NN

gr

0

H

w

Therapeutic effects

Fig 2.18 Therapeutic Effects of Topical Steroids

Reduced cell division

Reduced \ cellular activity Reduced lymphokine , \ activity /

Epidermis (Fig 2.18) Topical glucocorticosteroids cause a reduction in the rate of epidermal basal cell division. As has been described, the increased rate of epidermal proliferation (acanthosis) seen in lichenified atopic skin disease leads to the main structural and functional abnormalities of the condition. As cell division is reduced, so the epidermal architecture and physiology return to normal. Dermis (Fig 2.18) The steroid action in the dermis blocks the release of a variety of inflammatory substances from both white and mast cells, as well as blocking the effects of released substances (interstitial oedema, attraction of further neutrophils, and the generation of pruritus). The direct effect of glucocorticosteroid on the white blood cells of the inflammatory process is one of reduction in number, activity and secretion. Whether the observed local vasoconstriction associated with steroid action contributes to the therapeutic effect remains uncertain, but it is a curious fact that there is a direct correlation

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Profile for Christopher Bridgett

Atopic Skin Disease - A Manual For Practitioners  

An account of a new behavioural approach to the treatment of atopic eczema, written for practitioners, but also for patients

Atopic Skin Disease - A Manual For Practitioners  

An account of a new behavioural approach to the treatment of atopic eczema, written for practitioners, but also for patients