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Phototherapy
When patients have psoriasis that does not
respond to topical medications alone or have lesions that are too
extensive for topical treatment, phototherapy becomes an option. During
phototherapy, the patient’s skin or just the lesions are exposed to
ultraviolet light. Patients usually receive treatment in a
dermatologist’s office or psoriasis clinic. The types of phototherapy
used to treat psoriasis, include:
Excimer Laser
The excimer laser is effective in treating limited
plaque psoriasis and
offers two distinct advantages over other forms of phototherapy. First,
dermatologists can target the laser to treat only the psoriatic lesion,
which eliminates possible damage to surrounding unaffected skin.
Secondly, since only the lesions are treated, significantly higher doses
of light can be used, and higher doses allow for fewer treatment
sessions.
Approved by the U.S. Food and Drug
Administration (FDA) for the treatment of mild to moderate plaque
psoriasis, the excimer laser delivers high-intensity wavelengths of UVB
to the targeted plaques. Each treatment session typically lasts a few
minutes, and treatments are usually given twice a week. On average, 8 to
10 sessions are needed to achieve near clearance.
Patients considering laser treatment
should know that many states do not distinguish who can and cannot
perform procedures with laser and light sources. Since skin treatments
using lasers carry potential side effects, they should be performed by a
board-certified dermatologist or under direct physician supervision.
How it works: The ultraviolet (UV)
light produced by excimer lasers induces biologic reactions in the
skin’s cells that decrease the number of skin cells that grow too
quickly and reduce inflammation.
Advantages
- Well-tolerated
- See results quickly, sometimes in
2 weeks
- Fewer treatment sessions and
shorter treatment time than with traditional UV therapy
- Does not damage surrounding
healthy skin
- Effective on treatment-resistant
lesions, such as those that frequently occur on the elbows and
knees
- Most side effects mild: redness,
blistering, erosion
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Disadvantages
- Cannot treat entire body
- Treatment may be painful
- Darkening of the skin can occur
- Scarring possible
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Psoralen + Ultraviolet Light A (PUVA)
Also known as photochemotherapy, PUVA is effective in patients with
plaque,
guttate and palmar-plantar psoriasis and offers
long-lasting clearance to many who respond. Treatment requires the
patient to ingest, topically apply, or bathe in a medication called
(psoralen) before being exposed to UVA rays. Psoralen makes the skin more
sensitive to UVA rays. After treatment, patients must wear UVA blocking
sunglasses for the rest of the day when exposed to sunlight because
psoralen remains in the eyes for awhile.
About 25 treatments within 2 to 3 months
are needed before clearing occurs. Usually, 30 to 40 treatments per year
will keep psoriasis under control once it has cleared. Patients
undergoing PUVA treatment must be carefully monitored by dermatologists
and staff.
Due to the inconvenience and side
effects, PUVA is usually reserved for patients whose psoriasis has not
responded to other treatments or have widespread lesions.
How it works: Combining the
photosensitizing agent (psoralen) and UVA slows the rapid growth of skin
cells and kills T cells in the skin.
Advantages
- Offers long-lasting remission
- Effective in 85 to 90% of patients
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Disadvantages
- Requires numerous treatments in
medical office or clinic
- Patients must wear UVA-blocking
sunglasses when exposed to sunlight after treatment
- Increased risk of skin aging,
freckling and skin cancer with long-term treatment
- Side effects may include nausea,
headache, fatigue, burning skin, itching and irregular skin
pigmentation
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Ultraviolet B (UVB) Phototherapy
UVB phototherapy is highly effective in patients who have moderate to
severe psoriasis and thin plaques. Patients usually receive between 2
and 5 treatments per week. During treatment, the skin is exposed to UVB,
which is generated from a special lamp or laser. To enhance penetration
of UVB rays, an emollient is usually applied before exposure. UVB
phototherapy may be combined with another psoriasis therapy, such as
calcipotriene, tazarotene, anthralin or coal tar to increase
effectiveness. UVB phototherapy proves to have few side effects. There
are 2 types of UVB phototherapy:
- Broadband (3-5 treatments per week)
- Narrowband (2-3 treatments per week)
Broadband. This UVB therapy has
been around for more than 80 years, and it is still highly effective.
The biggest drawbacks are that the patient must travel between 3 and 5
times per week to a site that offers this therapy and that broadband
light does not reach the scalp and areas where skin folds occur.
Narrowband. This newer form of UVB
therapy is called “narrowband” because it emits a narrower band of UVB
wavelengths. Narrowband UVB therapy is proving to be more effective than
the traditional broadband therapy. However, it does have the potential
to produce severe burning. Like broadband, it is still not known if
narrowband UVB therapy poses a long-term risk for development of skin
cancer.
How it works: Ultraviolet (UV)
light induces biologic reactions in the skin’s cells that decrease the
number of skin cells that grow too quickly and kills T cells in the
skin, which can result in the clearing of psoriatic lesions.
Advantages
- Highly effective
- Few side effects
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Disadvantages
- Requires 2 – 5 weekly visits to a
clinic or medical office until lesions clear
- May require follow-up treatments
once lesions clear
- Long-term treatment may increase
risk of developing skin cancer
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References
Gribetz, C. et al. “Clearing Psoriasis: A New Era of Optimism.”
Contemporary Dermatology 2003: Vol. 1, No. 1: 1-8.
More Information
Topical Preparations
Covers topical medications, moisturizers and agents that remove excess
scale.
Systemic Medications
Information about FDA-approved systemic medications used to treat
psoriasis.
Other Systemic Medications
Research shows these drugs, which received FDA approval for treating
other conditions, may also be effective in clearing psoriasis.
AAD Consensus Statement on Psoriasis
Therapy
Table lists the treatments contained in the consensus statement
developed by leading dermatologists and other experts.
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