A short course in topical psoriasis agents

Plaque psoriasis is the most prevalent form of the disease.
Plaque psoriasis is the most prevalent form of the disease.

At a glance:

  • Prior to initiating therapy, consider the extent of the disease, lesion location, and the presence of psoriatic arthritis or other associated conditions.
  • Topical corticosteroids are the mainstay of treatment.
  • Patients on systemic antipsoriatic therapy, biologic therapy, or phototherapy are treated with topical agents as well.

Psoriasis is an extremely challenging condition to treat. While 83% of patients have mild, localized disease, most believe their problem is severe, and 85% of psoriasis sufferers are dissatisfied with their current treatment.

You must consider multiple factors prior to initiating therapy: extent of disease; lesion location; and presence of psoriatic arthritis or other associated conditions, such as diabetes, hypertension, or congestive heart failure.

Begin the initial consultation by evaluating the amount of involved body surface area (BSA). Each palm is equivalent to 1% of body surface. Each arm (including the hand) is 9%, each leg 18%, back 18%, chest 18%, face/scalp 9%, and groin 1%.

Mild psoriasis involves <3% of BSA, moderate psoriasis 3%-10%, and severe psoriasis >10%. Treating patients with >10% involvement solely with topical therapy is very difficult because the extent of application and quantity of medication required would be so great.

During the initial consultation, pay special attention to certain areas. Scalp involvement, for example, may cover only a small surface area, but patients will consider the problem disproportionately severe. Applying medication to the scalp can be difficult, which reduces compliance, and scalps are often more symptomatic with pruritus and frequently excoriated.

Psoriasis in the intertriginous areas needs special attention because of the areas' occlusive nature and the risk of atrophy. Hands and feet (Figure 1) are notoriously difficult to treat because hyperkeratosis interferes with medication penetration. Facial psoriasis (Figure 2) is uncommon, but its visibility can have a tremendous psychological effect and you'll need to approach this patient differently than other psoriasis patients.

It is also important to consider that even patients on systemic antipsoriatic therapy (methotrexate, cyclosporine, acitretin [Soriatane]), biologic therapy (efalizumab [Raptiva], etanercept [Enbrel], adalimumab [Humira], infliximab [Remicade], alefacept [Amevive]), or phototherapy (narrowband UVB, psoralen plus UVA) are being treated with topical agents as well. The previously mentioned therapies can be highly effective, but no therapy alone will produce total clearance, so all patients will require topical treatments.

I will assess only first-line topical therapy, which includes corticosteroids, vitamin D analogs, retinoids, and keratolytic agents. That leaves other effective therapies (i.e., tar, anthralin, calcineurin inhibitors, and occlusive dressings) for another day. This article will not cover treatment of special areas (e.g., scalp, hands/feet/genitals, intertriginous areas, and nails).

First-line mainstay

Topical corticosteroids are the mainstay of treatment. When deciding on the specific agent, consider the strength, vehicle formulation, and quantity required. The potency of the corticosteroid is classified by the vasoconstrictor assay and ranges from the strongest (class I) to the weakest (class VI).

New delivery systems based on altering the vehicle have had a significant impact on therapy. Not long ago, the vehicles included only ointments, creams, lotions, solutions, and gels, but now there are foams, sprays, and potentiated vehicles that use various techniques like microsponge delivery systems.

The vehicle affects not only the potency of an agent but also patient compliance, which is crucial for adequate response. Patients prefer lighter vehicles, such as lotions and foams, over heavy ointments. The new vehicles allow easier application to specific areas, e.g., hairy areas on the scalp or genitalia, increasing compliance.

Quantity is often neglected when prescribing topical medications. The average amount of medication required to cover an entire body is 30 g.

Understanding the extent of body coverage and providing adequate medication has a direct bearing on results. Inadequate quantity of medication reduces patients' ability to successfully treat their skin. This can be frustrating to the patient and reduce compliance.

Initial psoriasis treatment requires the use of the stronger classes of corticosteroids, classes I and II, to obtain adequate results. Start with a class I agent, e.g., clobetasol (Temovate) or halobetasol (Ultravate), in combination with either a vitamin D analog or keratolytic agent. The purpose is to start aggressively to gain control and then switch to a maintenance program for long-term control.

I instruct patients to apply the corticosteroid nightly, preferably as an ointment, which is occlusive and of greater potency, to maximize the response. For the morning, I prescribe application of a keratolytic agent in either a cream or lotion to thin the plaques. The choices include salicylic acid, lactic acid, or urea, all of which are effective. Patients try this treatment for four weeks and then I re-evaluate. At this point, I have an idea of the patient's response and I can focus on fine-tuning the therapy.

Following up, fine-tuning

If the patient is doing extremely well, I will switch to pulse application. The class I corticosteroid is applied b.i.d. on weekends and a class II-IV corticosteroid is applied Monday through Friday. The patient continues the keratolytic agent in the morning. Less medication will be required as the patient responds to treatment.

If the patient has not had an adequate response, I do not stop my initial approach but rather add to the program. I will initiate short-contact retinoid therapy, usually tazarotene (Tazorac). This strategy can be tricky because of tazarotene's irritation potential. I tell patients to apply the medicine three minutes prior to showering and gradually increase to a maximum of 10 minutes. It is very important to apply the medication only within the psoriatic plaque to avoid irritating surrounding skin.

Tazarotene is available in both cream and gel at two concentrations, 0.05% and 0.1%. I start with the 0.05% cream and have the patient apply the medication only to the more recalcitrant lesions, usually on the knees, elbows, and lower back.

A second change you can institute is switching the morning keratolytic agent to a vitamin D analog. The initial therapy will have reduced the scale and erythema, thereby preparing the psoriatic plaques for the vitamin D analog. I will then have the patient follow up in an additional four weeks.

At that appointment, I will fine-tune the program, often using the newer medications for specific areas. I find the clobetasol spray and foam vehicles are more effective than the traditional vehicles for recalcitrant areas. Also, a new combination of betamethasone and calcipotriene (Taclonex) ointment is available. This simplifies therapy and is particularly valuable applied on a nightly basis to existing plaques that have shown an initial response but have not resolved.

Psoriasis patients must be actively engaged in their treatment, and compliance is critical but often elusive. Treatment regimens can be complex and take time to work, patients are sensitive to cosmetic issues, and dispensed medication does not always last a full month. All of these factors make it more difficult to get patients to stay on the program. If you advise them to keep a treatment log, know that some will exaggerate their compliance.

For your part, treatment of psoriasis is complex and requires significant modifying and fine-tuning on an ongoing basis. Each patient will require individualized therapy frequently changed to meet his changing condition.

Dr. Greenberg is director of the East Bay Psoriasis Treatment Center in San Ramon, Calif.

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