Topical Therapy for the Management of Childhood Psoriasis: Part I

K. M. Cordoro, MD
Department of Dermatology, University of California, San Francisco, CA, USA

ABSTRACT

Psoriasis represents a potentially life-altering disease that can profoundly impact physical, emotional and social functioning, and overall quality of life. The majority of cases are mild and managed adequately with topical medications. A minor subset of children present with severe, rapidly evolving disease that requires systemic therapy. The choice of treatment in children, as in adults, is determined by disease acuity, morphology, distribution, severity and the presence of comorbidities such as psoriatic arthropathy. Practical considerations such as ease of use, patient acceptability, accessibility, risk to benefit ratio, cost and individual perceptions of disease and quality of life are factored into treatment decisions. Part I of this 2-part series will focus on topical agents, their varying degrees of effectiveness, potential side-effects and applications in clinical practice.

Key Words: anthralin, calcineurin inhibitors, calcipotriene/ calcipotriol, children, coal tar, corticosteroids, psoriasis, salicylic acid

Topical Therapy

Monotherapy may be effective for limited, focal or mild disease. In cases where multiple medications are necessary, the number of agents that must be applied can be reduced by compounding compatible agents. Research the surrounding community and keep a list of compounding pharmacies to provide to your patients. Ointment formulations tend to have greater efficacy than creams but some patients, particularly adolescents, find them objectionable. In an effort to increase compliance, prescribe whichever vehicle the patient finds preferable.¹ Thick, greasy ointments can be used at nighttime and more cosmetically acceptable creams, lotions and solutions reserved for daytime use.

Corticosteroids

Corticosteroids remain among the first line agents in the topical treatment of psoriasis in all age groups. Delivering the steroid to the involved skin in a convenient, tolerable, safe and efficacious manner requires selection of a vehicle that is well-suited to site-specific qualities such as hair (scalp), moisture (intertriginous zones) and occlusion (axillae, diaper area, gluteal cleft). A variety of vehicles are available to choose from and include powders, sprays, lotions, solutions, creams, emollient creams, ointments, gels, tape and foam.² Thin and intertriginous skin responds to lower potencies and thick hyperkeratotic areas such as the palms and soles require high potency agents. Infants have a large body surface area that increases the chance of systemic absorption and adverse events, such as adrenal suppression.³ In general, very high potency agents should be avoided in children, if possible, or used sparingly in combination or rotation with steroid sparing alternatives such as coal tar, anthralin, calcipotriene and topical calcineurin inhibitors.

Coal Tar

Crude coal tar has antipsoriatic, antiseborrheic, antipruritic and keratolytic effects.⁴ Given its better cosmetic acceptability, liquor carbonis detergens (LCD), a modified, less clinically active coal tar, has largely replaced crude coal tar in the outpatient setting. It can be compounded in an ointment, cream or solution vehicle in concentrations from 0.5% to 20%. Tar is a safe, effective treatment for childhood psoriasis and is supplied in a variety of topical formulations and shampoos. It can be used alone or compounded with corticosteroids, lactic and salicylic acid. Its safety, efficacy, and relatively low cost, compared with other topical agents are advantages in the long-term treatment of psoriasis. Side-effects of tar include folliculitis, irritation, and photosensitivity. It should not be used on acutely inflamed skin, or on pustular or erythrodermic psoriasis.⁵ There is no definitive evidence of an increased risk of skin cancer above the expected incidence for the general population from the use of therapeutic tar.^6,7 Education regarding the favorable safety profile and place in therapy as a steroid-sparing adjunct may increase tolerance and compliance of this excellent and underutilized topical therapy.

Anthralin

Anthralin (dithranol) is a potent anti-inflammatory and anti-proliferative agent.⁸ It is a synthetic version of chrysarobin, a natural substance derived from the araroba tree of South America used to treat psoriasis for nearly 100 years.⁹ Negligible systemic absorption is responsible for its excellent safety profile and ease of use, especially in children. Its use has been limited due to staining and irritation, but short contact and “minutes” therapy are popular, less messy alternatives (increasing concentrations [0.1% to 3%] of dithranol applied to the skin and left in place for 10-30 minutes daily until a slight irritation develops, then hold dose/time until clear¹⁰). Lower concentrations or less contact time should be maintained on more sensitive sites such as anogenital skin.

Calcipotriene

Calcipotriene (calcipotriol in Europe and Canada) is an analog of vitamin D3 that has been proven safe and effective in adults with psoriasis. It is an efficient nonsteroidal alternative and has utility as monotherapy as well as in novel sequential and rotational combinations with topical steroids.¹¹ Calcipotriol ointment has been shown to be effective, well tolerated and safe in children with psoriasis, with local irritation the most commonly reported side-effect.^12-15 Adverse effects of topical calcipotriol on systemic calcium homeostasis in adult patients with chronic plaque psoriasis has been evaluated and is related to dose per unit body weight of the patient.¹⁶ Though no formal guidelines exist for children, use of up to 45g/week per m2 in children does not seem to influence serum ionized calcium levels.¹³ Regimens combining calcipotriene and topical steroids, such as once daily use of each or twice daily use of calcipotriene on weekdays and steroids on weekends only, are steroid sparing and superior in efficacy to twice daily monotherapy with either agent.^17,18 Calcipotriene destabilizes in the presence of salicylic acid, ammonium lactate, and hydrocortisone valerate 0.2% ointment and thus, should not be used at the same time as or compounded with these molecules.¹⁹

Tazarotene

Tazarotene is a third-generation topical retinoid US FDA-approved for once daily treatment of psoriasis in adults aged 18 and older and acne vulgaris in patients aged 12 and above. Similar to other retinoids, tazarotene restores normal epidermal differentiation and proliferation and reduces epidermal inflammation.²⁰ Limit its use to thicker plaques on non-intertriginous sites. Tazarotene is neither sensitizing nor phototoxic, but dose-related skin irritation is common and often necessitates combination with a topical steroid applied at a different time of day. Short contact (10-60 minutes per day, then wash off), alternate day or weekly applications are potential ways to include this useful agent in sequential and rotational regimens. Effectiveness of tazarotene for nail psoriasis has been demonstrated clinically in adults²¹ and children.²²

Topical Calcineurin Inhibitors

Tacrolimus and pimecrolimus are nonsteroidal immunomodulating macrolactams that work by blocking the enzyme calcineurin, ultimately inhibiting the downstream production of IL-2 and subsequent T-cell activation and proliferation.²³ Both topical agents are currently FDA approved for second line intermittent treatment of atopic dermatitis in patients aged 2 years and older (pimecrolimus and tacrolimus 0.03%) and aged 15 and older (tacrolimus 0.1%). They are effective, safe and well tolerated therapeutic options for psoriasis at sites more sensitive to the long-term adverse effects of topical steroids such as the face, flexures, and anogenital region.^24-27

Salicylic Acid

Salicylic acid is a useful adjunctive keratolytic agent for very thick localized plaques arising on the scalp, palms and soles. It should be used sparingly and with caution in the pediatric population because of the risk of percutaneous salicylate intoxication.²⁸ Avoid its use altogether in infants and children less than 6 years old.

Conclusion

Treatment of childhood psoriasis is both challenging and rewarding. Medical management remains primarily anecdotal as most therapies are neither studied nor approved for use in children. At our disposal are both traditional and new topical agents that can be used in diverse ways as monotherapy or in combination. Treatment decisions must be individualized for each patient based on thorough assessment of the disease, comorbidities, and impact on quality of life.

References

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In this issue:

1. Topical Therapy for the Management of Childhood Psoriasis: Part I
2. Advances in Pemphigus Therapy
3. Update on Drugs and Drug News - April 2008