UVB for Psoriasis
quotes from http://www.clevelandclinicmeded.com/diseasemanagement/dermatology/psoriasis/psoriasis.htm
Phototherapy is highly effective, clearing 80% to 100% of the skin. However, some maintenance therapy is usually necessary.8 The disadvantages to this treatment method are that it requires specialty equipment and care, the need for two or three office visits a week, and is expensive. Additionally, it carries a short-term risk of sunburn and a theoretical long-term risk of skin cancer.
Natural sunlight and UVA tanning beds are mildly therapeutic. Ultraviolet B (UVB) phototherapy is given by dermatologists in the office or clinic. It is reserved for patients with widespread lesions involving 10% or more of the BSA. Specialized training is necessary for the safe delivery of phototherapy.
The Goeckerman regimen, first described in 1925, used a combination of broadband UVB (290 nm to 320 nm) phototherapy and crude coal tar. However, a 1981 study found that nonerythemogenic protocols of broadband UVB therapy used with a bland ointment, such as petrolatum or mineral oil, was equally as effective at clearing psoriasis. The study showed that the erythema spectrum for UVB was below 300 nm and that the therapeutic action spectrum was between 300 nm and 313 nm.9 In 1984 a fluorescent lamp (Philips TL-01) was designed to emit UVB at 311nm to 313nm, which is now known as narrowband UVB. Several studies have shown that narrowband UVB phototherapy is more effective more rapidly than broadband UVB therapy.
Our clinic uses the modified protocol described by Shelk and Morgan10, treating patients three times weekly until their skin is nearly clear followed by maintenance one to two times weekly. Narrowband UVB phototherapy is probably not as efficacious as PUVA but is perceived to be safer because no internal photosensitizer is used. Moreover, broadband UVB therapy has had a long track record of safety since 1925, whereas PUVA has been found to be associated with squamous cell carcinoma.
Recent US Food and Drug Administration (FDA) approval of the 308-nm xenon chloride excimer laser has enhanced narrowband UVB therapy. In a pilot study of the XTRAC (PhotoMedex)11, psoriasis cleared after 8 treatments; however, 30 narrowband UVB treatments were required to achieve the same effect. The cumulative dose for the laser was one sixth that of narrowband UVB. A second study showed that higher fluences produced significantly better results and fewer recurrences at 4 months follow-up; however, higher fluences may cause blistering reactions. Disadvantages to this modality are that the aperture of the handpiece is 4 cm2 (limiting practical use to patients with less than 10% BSA involvement); unproven efficacy in specialized areas such as the scalp, palms, and soles; and unknown long-term side-effects.
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Vitamin D3 and Analogs
Topical vitamin D3 (calcitriol) and the topical synthetic analogs calcipotriene and tacalcitol are effective for plaque-type psoriasis and are free of any serious toxicity.21 In double-blind studies, patients applied calcipotriene to one side of their body and corticosteroids to the other side. Calcipotriene was equivalent to or better than medium-strength and potent corticosteroid ointments, without the risk of skin atrophy or rebound flare-ups on discontinuation of therapy.
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Level 3: Systemic:
Although systemic treatments are more effective than level 2 treatments, they are often more expensive and have greater potential for toxicity. Systemic treatments are generally prescribed only by a dermatologist.
Photochemotherapy or PUVA was first reported as a novel treatment for psoriasis in a landmark article in 1974.14 The photosensitizer, 8-methoxypsoralen (8-MOP), is taken orally 1.5 to 2 hours before UVA exposure. The drug is excited by the UVA irradiation in the 320-nm to 390-nm wavelength range. This produces crosslinking of DNA strands, thereby inhibiting DNA synthesis and epidermal turnover, which leads to healing of psoriasis.
Long-term follow-up of PUVA-treated patients has conclusively demonstrated the carcinogenic potential of PUVA for squamous cell carcinoma with the greatest risk for male genitalia. The latter must now be shielded during treatment. These patients also developed pigmented macules, called PUVA lentigines, in exposed areas. One study group reported that the incidence of malignant melanoma is increased in patients who received more than 250 PUVA treatments and were followed for more than 15 years. Although their results have not been confirmed by other investigators, dermatologists have sought to treat patients with alternatives perceived to be safer, such as bath PUVA.
In bath PUVA, the 8-MOP solution is dissolved in bath water, and the patient is soaked for 30 minutes before UVA exposure. Systemic absorption is negligible, and it is not necessary for the patient to wear UV protective glasses for the remainder of the day. The psoralen must be dispensed in the office. Most offices are not set up to give full body baths, however, this treatment is highly effective for psoriasis of the palms and soles, which is usually recalcitrant. Palms and soles are soaked in basins in an examination room and followed by twice-weekly exposure to hand-foot UVA-delivery units. The formula is 0.4 mL of 1% methoxsalen (Oxsoralen) solution diluted in 1.5 L tap water.15 If necessary, this treatment can be enhanced with 10-25 mg daily acitretin, an oral retinoid.
