Essential Insights On Treating Psoriatic Lesions In The Lower Extremity

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M. Joel Morse, DPM

   Calcipotriene 0.005% (Dovonex, Warner Chilcott) is a vitamin D3 analogue that inhibits epidermal cell proliferation and enhances cell differentiation. It is available as a cream and recently came out as a foam. Most studies show that calcipotriene is not as effective as group I corticosteroids but regimens using calcipotriene and group I corticosteroids are superior over either agent alone.32

   Most patients now use the following regimen. Apply calcipotriene in the morning and a group I corticosteroid in the evening for two weeks. Then begin a maintenance regimen using group I corticosteroids twice daily on weekends and calcipotriene twice daily on weekdays. Application for six to eight weeks gives a 60 to 70 percent improvement in plaque-type psoriasis.32

   Topical steroids are in use most often for plaque and palmoplantar psoriasis. Topical steroids give fast but temporary relief. They are most useful for reducing inflammation and controlling itching. Initially, when the patient is introduced to topical steroids, one will usually see spontaneous clearing of the skin in a few treatments. However, tachyphylaxis or tolerance occurs, and the medication becomes less effective with continued use.

   Ultrapotent topical corticosteroids are the mainstay of podiatric psoriasis treatment, whether one uses them as monotherapy or in combination with a topical vitamin D analogue. The more common ones include betamethasone dipropionate (Diprosone, Diprolene, Schering Plough) and clobetasol (Clobex, Galderma Laboratories). My patients use them twice a day for two weeks to resolve inflammation and pruritus.

   When it comes to psoriasis, ointment is the most common treatment vehicle because of its soothing effect and occlusive nature. Ointments also provide the highest potency for any dermatoses. However, a recent study showed that betamethasone dipropionate 0.05% in optimized cream used once a day compared well with the standard betamethasone ointment.33

   Recent studies demonstrate that poor adherence to topical treatment is common among patients with psoriasis and contributes to poor treatment outcomes. Non-ointment topical corticosteroid products exhibit excellent efficacy in clinical practice.

   Much of the poor outcomes in psoriasis, even tachyphylaxis, likely relate less to actual medication failure and more to failure to apply the medication.34 Topical psoriasis treatment is likely to be more successful when podiatrists and patients discuss what type of vehicle the patient will use and plan treatment accordingly. Almost any lesion of psoriasis can completely resolve with topical therapy alone when clinicians use traditional tar preparations, anthralin (Dithranol) or topical corticosteroids with or without salicylic acid.35

   Topical retinoids are thought to normalize abnormal keratinocyte differentiation, reduce epidermal hyperproliferation and decrease inflammation, resulting in a more normal expression of skin differentiation in psoriatic lesions. As podiatrists, we routinely use calcipotriene, a vitamin D analogue and less frequently use other active forms of vitamin D like calcitriol and tacalcitol (Curatoderm). One can also use the vitamin A analogues isotretinoin and acitretin (Soriatane, GlaxoSmithKline).

   In one study, topical tazarotene (Stiefel), a topical retinoid (0.1% cream), was less effective than topical clobetasol propionate 0.05% cream in the treatment of plaque psoriasis.1

How Effective Is Combination Therapy?

The prevailing thinking is that a combination approach enhances the efficacy of the vitamin D analogue and limits the toxicity of the corticosteroid.

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