Medical Treatment of Psoriasis
Since psoriasis is incurable, the selection of treatment plans must consider the long-term outlook. Treatment options depend on the extent and severity as well as the emotional response to the disease. They include topical agents (drugs applied to the skin), phototherapy (controlled exposure to ultraviolet light), and systemic agents (orally, intravenously, or percutaneously administered agents). All of these treatments may be used alone or in combination with one another. Psoriasis in children younger than 15 years of age is rare; therefore, the following review is confined to adult options.
Topical agents: Medications applied directly to the psoriatic skin lesions are the safest approaches to treatment but are only practical if treating localized disease. The most popular topical treatments are corticosteroids (in vehicles such as foams, creams, gels, liquids, sprays, or ointments), calcium modulators, coal tar extracts, and anthralin. There isn't one topical drug that is best for all people with psoriasis. Because each drug has adverse effects or limited efficacy, it may be necessary to rotate them. Sometimes topical preparations are combined together. For example, keratolytics (substances used to break down scales or excess skin cells) are often added to these preparations to enhance their penetration into the skin. Some preparations should never be mixed together because they interfere with each other. For example, salicylic acid inactivates calcipotriene cream or ointment. On the other hand, drugs such as anthralin (tree bark extract) may require the addition of salicylic acid to work effectively.
Phototherapy (light therapy): Ultraviolet (UVL) light, a portion of the solar spectrum with wavelengths between 290-400 nm, can have beneficial effects on psoriatic skin presumably by altering certain immune functions. Disease that is considered too extensive to be treated by topical approaches, that is usually greater than 5%-10% of the total body surface area, is an appropriate indication for this sort of treatment. Resistance to conventional topical treatment is another indication for light therapy. Although normal sunlight contains these wavelengths, self-exposure to sunlight must be done in under controlled conditions to minimize burns. In a physician's office, control of the amount of light energy administered to each patient is essential. Medical light sources use special wavelengths of light and timers to assure the correct dosage of light. Sunlamps and tanning booths are not acceptable substitutes for medical light sources. Ultraviolet light from any source is known to produce skin cancer, but this side effect is minimized when the light is appropriately administered in a physician's office.
- UV-B: Ultraviolet B (UV-B) light is used to treat psoriasis. UV-B is light with wavelengths of 290-320 nanometers (nm), shorter than the range of visible light. (Visible light ranges from 400-700 nm.) UV-B therapy may usually be combined with one or more topical treatments. UV-B phototherapy is effective for treating moderate-to-severe plaque psoriasis. The major drawbacks of this therapy are the time commitment required for treatments and the accessibility of UV-B equipment. With long-term use, there is a risk of skin cancer, just as there is from natural sunlight.
- The Goeckerman regimen uses coal tar followed by UV-B exposure and has been shown to produce improvement in more than 80% of patients. The odor of coal tar limits its popularity. The treatments involve twice-a-day light exposure plus daily application of the tar preparation for two to four weeks. This is no small commitment and either requires hospitalization or using a psoriasis day-care treatment center.
- In the Ingram method, the drug anthralin is applied to the skin after a tar bath and UV-B treatment.
- UV-B therapy can be combined with the topical application of corticosteroids, calcipotriene (Dovonex), tazarotene (Tazorac), or creams or ointments that soothe and soften the skin.
- Narrow-band UVB light sources produce wavelengths of ultraviolet light at about 313 nm, which seems to be particularly effective for controlling psoriatic plaques while minimizing side effects. It rivals PUVA in its efficacy.
- PUVA: PUVA is the therapy that combines a psoralen-containing oral medication with ultraviolet A (UV-A) light therapy. Psoralens make the skin more sensitive to long-wave UVA (320-400 nm). Methoxsalen (Oxsoralen) is a psoralen that is taken by mouth before UV-A light therapy. More than 85% of patients report relief of disease symptoms with 20-30 treatments. Therapy is usually given two to three times per week on an outpatient basis, with maintenance treatments every two to four weeks to maintain remission. Adverse effects of PUVA therapy include nausea, itching, and burning. Long-term complications include increased risks of sensitivity to the sun, sunburn, skin cancer, skin aging and cataracts. Protective glasses must be worn during and after treatment to prevent cataracts. PUVA therapy is not used for children younger than 12 years of age.
Systemic agents (drugs taken orally or administered by injection or intravenous infusion): These drugs are often started after both topical treatment and phototherapy have been carefully considered. Certain systemic agents are also very effective in controlling psoriatic arthritis. People whose disease is disabling because of physical, psychological, social, or economic reasons may also be considered for systemic treatment.