Psoralen and UVA light therapy (PUVA) for psoriasis
Psoralen medicines are available as pills, lotions, or bath salts. A psoralen medicine is taken 1½ to 2 hours before you are exposed to ultraviolet A (UVA) light (PUVA). This treatment is repeated 2 to 3 times a week. The dose of medicine is not increased, but the amount of light may be increased.
Goggles should be worn to protect eyes during UVA treatment. Special UVA-blocking glasses should be worn for 24 hours after PUVA therapy. Men should protect their genitals from UVA exposure during treatments.
Psoralens may also be used in a form that can be put into your bath water. This form causes greater sensitivity to UVA than the oral medicine, so lower doses of UVA can be used.
How It Works
Psoralens increase the skin's sensitivity to UV light, including sunlight. They are used to improve the effectiveness of UV light therapy for psoriasis.
It is thought that PUVA therapy reduces the excess growth of skin cells. It also weakens the immune system.
Why It Is Used
PUVA is used to treat moderate to severe psoriasis (covering more than 20% of the skin).
PUVA is used to treat psoriasis that has not responded to creams, ointments, or tar products used with UV exposure (phototherapy). It should be used in the lowest doses possible. Higher doses and more exposure increase the risk of skin cancer.
Psoralens should not be used by:
- Children under age 12, because the UV light therapy may cause cataracts.
- People who have diseases that make their skin more sensitive to sunlight (such as lupus).
- Fertile men and women who do not use birth control. There is a small risk of birth defects.
- Pregnant women, because of possible effects on a fetus.
How Well It Works
When PUVA is used to treat psoriasis, short-term side effects include:
- Skin redness, headache, nausea, and itching.
- The spread of psoriasis to skin that was not affected before (Koebner's response).
- Nausea from the medicine.
The most significant potential long-term effect of PUVA treatment is an increased risk of some types of cancer.
- PUVA treatments with cyclosporine have shown a significant increase in the risk of squamous cell cancer.3 A serious form of skin cancer, melanoma, has also been reported.
- The male genitals are highly susceptible to the cancer-causing effects of both PUVA. Female genitals do not seem to be affected.
Other long-term side effects when using PUVA to treat psoriasis include:
- Premature skin damage associated with sun exposure.
- Discolored spots on the skin.
- Overgrowth of the scaly layer of skin caused by exposure to sunlight (actinic keratosis).
- Cataracts. Cataracts may be avoided by wearing goggles during UVA treatments and sunglasses that block UV light when outdoors.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Psoralens applied to the skin (topical) may help to avoid some side effects of oral medicines used for PUVA. They may be especially helpful when psoralens taken by mouth (oral) cause severe nausea. Topical psoralens may be used for psoriasis that affects only a small part of the skin.
Topical psoralens, such as those given in bath water, are as effective as oral psoralens. But if light treatments are given in a doctor's office, they may be less convenient.
- Chuang GS, Gottlieb A (2009). Papulosquamous disorders. In RE Rakel, ET Bope, eds., Conn's Current Therapy 2009, pp. 801–805. Philadelphia: Elsevier Saunders.
- Abel E, Lebwohl M (2008). Psoriasis. In EG Nabel, ed., ACP Medicine, section 2, chap. 3. Hamilton, ON: BC Decker.
- Naldi L, Rzany B (2009). Psoriasis (chronic plaque), search date August 2007. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
Last Revised: January 7, 2010
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