Dermatology Online Journal

Keratolytics for psoriasis: Are they necessary?
Richard McClain MD¹, Brad A Yentzer MD¹, Steven R Feldman MD PhD^1,2
Dermatology Online Journal 15 (1): 11

1. Department of Dermatology
2. Department of Pathology and Department of Public Health Sciences
Center for Dermatology Research, Wake Forest University School of Medicine, Winston-Salem, North Carolina. sfeldman@wfubmc.edu

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Abstract

It is a common belief that keratolytic agents are required to enhance the penetration of topical medications into thick psoriatic plaques. However, is this belief evidence-based?

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Dogma teaches that thick scaly psoriatic plaques, especially those of the scalp, must first be treated with a keratolytic agent to remove excess scale and facilitate penetration of other topical treatments. Rook's Textbook of Dermatology states "even the most potent [corticosteroid] is useless if painted on the surface of thickly heaped-up psoriasis" [1]. Habif's Clinical Dermatology, 4th ed. states that "[scalp] scale must be removed first to facilitate penetration of medicine. Superficial scale can be removed with shampoos that contain tar and salicylic acid" [2]. Dermatology by Bologna et al. asserts, "If the psoriatic plaques have thick scale, then it needs to be reduced to enhance penetration of topical medications" [3].

To assess this dogma, we reviewed scalp psoriasis clinical trials that did not use a keratolytic or other scale-removing treatment. In these trials, even thick scalp psoriatic plaques improve rapidly with topical corticosteroids alone. A randomized, multicenter, study of twice daily betamethasone lotion and clobetasol propionate solution in the treatment of moderate-to-severe scalp psoriasis included 193 subjects with an average "scaling" score of 2.4 out of 3 [4]. The scale score decreased to 0.5 (and overall severity decreased from 8.4 to 1.5 out of 12) with 2 weeks of betamethasone treatment and to 0.7 with clobetasol (overall disease severity decreased from 8.7 to 2.3 out of 12). No keratolytics were used. In a similar study of 241 patients with scalp psoriasis and a baseline "scaling" score of 2.4/3 treated with betamethasone valerate 0.12 percent foam, 88 percent achieved complete or near-complete resolution in 4 weeks [5]. Four weeks of clobetasol propionate 0.05 percent shampoo in subjects with moderate to severe scalp psoriasis reduced global severity scores from 6.2 to 3.1 (out of 9) [6]. Similar findings of very good efficacy of clobetasol preparations for scaly plaques of psoriasis on non-scalp sites, in the absence of keratolytic treatment, have been observed in numerous clinical trials [7-10].

Whereas keratolytics do have some efficacy in treating psoriasis, the clinical trial data show that thick, scaly psoriasis lesions do respond well to topical corticosteroids alone. The high efficacy of topical corticosteroids for even very thick psoriatic plaques should be expected given the poor barrier function of lesional skin [11, 12]. The dogma that keratolytics are "needed" to treat thick psoriatic plaques may be too strong of an assertion. Most psoriatic plaques, even very thick lesions, can be treated rapidly and effectively with high-potency topical corticosteroids alone in clinical trials. The resistance of some psoriasis plaques in clinical practice is probably more a function of poor compliance than it is poor penetration. Although de-scaling agents may enhance efficacy in some clinical trials, the added complexity of treatment in clinical practice may reduce compliance and worsen outcomes. Perhaps Rook's Textbook of Dermatology would be more accurate if it said, "even the most potent [corticosteroid] is useless if NOT painted on the surface of thickly heaped-up psoriasis."

References

1. Rook A, Burns T, Breathnach S, Cox N, Griffiths C: Rook's textbook of dermatology. ed 7th, 2004.

2. Habif TP: Psoriasis and other papulosquamous diseases; Clinical dermatology : a color guide to diagnosis and therapy. Philadelphia, Mosby, 2004.

3. Bolognia J, Jorizzo JL, Rapini RP: Dermatology. New York, Mosby, 2003.

4. Katz HI, Lindholm JS, Weiss JS, Shavin JS, Morman M, Bressinck R, Cornell R, Pariser DM, Pariser RJ, Weng W, .: Efficacy and safety of twice-daily augmented betamethasone dipropionate lotion versus clobetasol propionate solution in patients with moderate-to-severe scalp psoriasis. Clin Ther 1995;17:390-401. [PubMed]

5. Andreassi L, Giannetti A, Milani M: Efficacy of betamethasone valerate mousse in comparison with standard therapies on scalp psoriasis: an open, multicentre, randomized, controlled, cross-over study on 241 patients. Br J Dermatol 2003;148:134-138. [PubMed]

6. Griffiths CE, Finlay AY, Fleming CJ, Barker JN, Mizzi F, Arsonnaud S: A randomized, investigator-masked clinical evaluation of the efficacy and safety of clobetasol propionate 0.05% shampoo and tar blend 1% shampoo in the treatment of moderate to severe scalp psoriasis. J Dermatolog Treat 2006;17:90-95. [PubMed]

7. Broby-Johansen U, Karlsmark T, Petersen LJ, Serup J: Ranking of the antipsoriatic effect of various topical corticosteroids applied under a hydrocolloid dressing--skin-thickness, blood-flow and colour measurements compared to clinical assessments. Clin Exp Dermatol 1990;15:343-348. [PubMed]

8. Reygagne P, Mrowietz U, Decroix J, de Waard-van der Spek FB, Acebes LO, Figueiredo A, Caputo R, Poncet M, Arsonnaud S: Clobetasol propionate shampoo 0.05% and calcipotriol solution 0.005%: a randomized comparison of efficacy and safety in subjects with scalp psoriasis. J Dermatolog Treat 2005;16:31-36. [PubMed]

9. Beutner K, Chakrabarty A, Lemke S, Yu K: An intra-individual randomized safety and efficacy comparison of clobetasol propionate 0.05% spray and its vehicle in the treatment of plaque psoriasis. J Drugs Dermatol 2006;5:357-360. [PubMed]

10. Angelo JS, Kar BR, Thomas J: Comparison of clinical efficacy of topical tazarotene 0.1% cream with topical clobetasol propionate 0.05% cream in chronic plaque psoriasis: a double-blind, randomized, right-left comparison study. Indian J Dermatol Venereol Leprol 2007;73:65. [PubMed]

11. Serup J, Blichmann C: Epidermal hydration of psoriasis plaques and the relation to scaling. Measurement of electrical conductance and transepidermal water loss. Acta Derm Venereol 1987;67:357-359. [PubMed]

12. Schaefer H, Zesch A, Stuttgen G: Penetration, permeation, and absorption of triamcinolone acetonide in normal and psoriatic skin. Arch Dermatol Res 1977;258:241-249. [PubMed]

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