Laser Treatment Promising in Psoriasis, June 10, 2002 -- The 308-nm excimer laser may prove to be the treatment of choice for vitiligo and psoriasis, based on results of two pilot studies reported in the May issue of the Journal of the American Academy of Dermatology. In a separate study, the same laser offered psoriasis patients more rapid response with less long-term risk to healthy skin than is typically seen with standard therapy using psoralen plus ultraviolet A. With 308-nm UV-B radiation generated by an excimer laser, it is possible to clear psoriasis with as little as 1 treatment with moderately long remission. In contrast to traditional phototherapy techniques, this handheld excimer laser UV-B therapy is selectively directed toward lesional skin, thus sparing the surrounding normal skin from unnecessary radiation exposure. Treatment of other inflammatory diseases and limited psoriasis seems reasonable to pursue with this modality. A recent study showed that a laser beam of ultraviolet light can clear psoriasis patches in a single treatment with a fairly long remission, but blistering was common
Also by experiment the use of 1% ALA-PDT ( Topical aminolaevulinic acid-based photodynamic therapy ) in combination withlight doses ranging from 5 to 20 J cm ) was investigated for chronic localized plaque type psoriasis. An unsatisfactory clinical response, a slow pace of improvement and the frequent occurrence of pain during and after irradiation renders topical ALA-based PDT( which lead to formation protoporphyrin IX (PpIX) an inadequate treatment option for psoriasis. Alternative photodynamic regimens such as systemic ALA in combination with blue light or systemically administered verteporfin in combination with red light might provide better therapeutic results. However, the effectiveness of such alternative approaches has yet to be substantiated by controlled studies in larger series of patients
Psoralen and UVA light therapy (PUVA), which combines UVA exposure and a medicine (called a psoralen) that makes your skin more sensitive to lightand useful for localised palmoplantar pustular psoriasis PUVA (the use of psoralen medicines with UVA light therapy) is usually used when psoriasis is disabling and safer treatments have not worked. It’s known that coumarin deravatives (psoralen) from ammi majus (medicinal plant) associated with UV light used in treatment psoriasis through many effects ,for example it’s a planner compound can interact with DNA molecules: it was reported that interstrand cross –links are formed in native DNA by irradiation with 360 nm light in the presence of psoralen ,and suggested that the cross-link may result from the reaction of an excited psoralen molecule with pyrimidine bases in opposite strands of the DNA duplex. Only linear psoralens such as psoralen, 8-methoxy psoralen, 5-methoxypsoralen and the synthetic 4,5' -8-trimethylpsoralen (TMP) are used in photo chemotherapy.
There is a bath PUVA and an oral PUVA. Bath PUVA therapies involve soaking in a bath of psoralens liquid for 15 minutes prior to UVA treatment. Oral PUVA involves taking an oral psoralens capsule the day prior to a UVA treatment. Oral psoralens such as methoxsalen cause nausea in many patients. Other adverse effects of PUVA include photosensitivity, which necessitates the use of eye protection and UVA-blocking sunscreen for 24 hours after a PUVA treatment; macular melanosis at exposed sites (PUVA lentigines); and increased risk of skin cancers, especially squamous cell carcinoma.
PUVA has been used in conjunction with other topical agents to increase treatment efficacy. Calcipotriol when added to a regimen of PUVA may reduce the number of PUVA treatments and the total UVA dosage needed for clearing lesions. The rate ratio for marked improvement in patients receiving PUVA plus calcipotriol versus PUVA alone was 1.2 in a recent meta-analysis of 11 controlled studies. If calcipotriol and PUVA are used together, calcipotriol must be applied after PUVA, since irradiation with UVA will inactivate calcipotriol. One small study of PUVA with tazarotene in 12 patients with extensive plaque psoriasis showed a statistically significant improvement after 3 weeks; however, UVA doses should be reduced by at least one-third if tazarotene is added, since it increases the risk for immediate pigment darkening caused by UVA. Coal tars are photosensitizing and are not generally used with PUVA, and PUVA plus topical corticosteroids have yielded conflicting results.
Rotational therapy / Sequential (i.e., rotating systemic drug interventions in a sequential manner) is a means to minimize drug-associated toxicities, since systemic agents for psoriasis often have differing toxicities. This may be considered for psoriasis patients who require systemic treatments long-term to manage their condition. Systemic therapies are optimally used in a rotating fashion to minimize drug toxicities (e.g., methotrexate–acitretin–cyclosporine or methotrexate–PUVA–acitretin) Sequential therapy involves rapid clearing of psoriasis with aggressive therapy (e.g., cyclosporine), followed by a transitional period in which a safer drug such as acitretin is started at maximal dosing. Subsequently, a maintenance period using acitretin in lower doses or in combination with UVB or PUVA can be continued.
You must be aware with these risks when using this therapy
Skin cancer. UVB is the part of sunlight that causes suntans, sunburns, skin damage, and aging. Exposure to UVB light can also lead to skin cancer and can cause serious eye damage. The risk of skin cancer increases with the amount of exposure to UV light. Your dermatologist will monitor your overall exposure to UV rays
Skin damage. Long-term exposure to UVA light may lead to skin damage, aging, skin cancer, and cataracts. This risk of cataracts can be reduced by regular use of sunglasses that block UVA light when you are outdoors. Cancer, The male genitals are highly susceptible to the cancer-causing effects of both PUVA therapy and UVB therapy.For people who have erythroderma or pustular psoriasis, UV treatment may make the condition worse.
Phototherapy or photochemotherapy is used for patients with moderate to severe psoriasis, generally when topical therapies alone are inadequate. Photochemotherapy is the concurrent use of phototherapy together with topical agents or systemic drugs. Phototherapy of psoriasis involves the use of either ultraviolet A (UVA) or ultraviolet B (UVB).
Niels Finsen was the first physician to investigate the therapeutic effects of sunlight scientifically and to use sunlight in clinical practice. This became known as phototherapy.Sunlight contains many different wavelengths of light. It was during the early part of the 20th century that it was recognized that for psoriasis the therapeutic property of sunlight was due to the wavelengths classified as ultraviolet (UV) light. Ultraviolet wavelengths are subdivided into UVA (380–315 nm) UVB (315–280 nm), and UVC (< 280 nm). Ultraviolet B (UVB) (315–280 nm) is absorbed by the epidermis and has a beneficial effect on psoriasis.
Narrowband UVB (311 to 312 nm), is that part of the UVB spectrum that is most helpful for psoriasis. Exposure to UVB several times per week, over several weeks can help people attain a remission from psoriasis. Ultraviolet light treatment is frequently combined with topical (coal tar, calcipotriol) or systemic treatment (retinoids) as there is a synergy in their combination.
Ultraviolet B (UVB) light is more effective than UVA light for treating psoriasis, Exposure times start at 30 to 60 seconds and are gradually increased until light causes the skin to turn red. When the skin no longer turns red after this much exposure, the time is increased. Treatments are given daily or several times a week. UVB light is used alone, with tar products (Goeckerman treatment), or with anthralin applied to the skin (Ingram regimen).UVB light alone (without drugs) is used for widespread plaque psoriasis and guttate psoriasis..
Ultraviolet A (UVA) penetrates deeper into the skin than UVB Treatment with UVA typically takes 20 minutes for a session UVA light used with psoralen drugs is called PUVA. With PUVA, the treatment time is greatly reduced, from 20 minutes to about 2 minutes
Phototherapy may be given at locations such as a hospital or doctor's office, a psoriasis day care center, or your home (UVB). In general, your entire body is exposed to the light. (If psoriasis affects only certain areas of your body, UV light may be directed at these selected areas only.) You will wear sunglasses that block UV light and goggles or a blindfold to protect your eyes from getting cataracts. Men may also need to shield their genitals to protect them from an increased risk of genital cancer.
In other study reported that NB-UVB penetrates more deeply into the skin than broad-band UVB and is therefore highly effective for the treatment of psoriasis vulgaris. It is also less carcinogenic and has become popular as routine phototherapy in many countries around the world. Narrowband ultraviolet B (NB-UVB) irradiation is frequently the treatment of choice in mild to moderate cases of psoriasis vulgaris . Its therapeutic effects involve several mechanisms, including the induction of anti-inflammatory and immunosuppressive cytokines can effectively induce the apoptosis of T cell within corium and inhibit Langerhans cell’s antigen presentation and effect of activating T cell, can escape from DNA absorption peak (about 265mm) and consequently decrease carcinogenicity. Reported by Tzung et al, at the same radiation dose level, UVB may cause more serious DNA damage than NB-UVB; to achieve the same therapeutic effect, the radiant dose of NB-UVB is 10 times higher than UVB, but there is no significant difference of DNA damage caused by the two; in addition, erythema effect of NB-UVB is slighter than conventional UVB.
It is reported that the wave length most prone to cause erythema effect is about 300 nm, and discovered by the experiment on healthy volunteers that Joule amount for NB-UVB to cause the smallest erythema is 4 times of UVB, which indicate NB-UVB is less prone to cause erythema effect. Revealed by the study, the effective rate of NB-UVB radiation on psoriasis vulgaris is 83.7%, which is similar with the domestic and overseas reports, while the effective rate of UVB radiation on psoriasis vulgaris is only 37.9%, which indicates NB-UVB is with better therapeutic effect and fewer adverse effect than UVB, and NB-UVB radiation is one of the primary methods for treating psoriasis . NBUVB could be used in pregnancy, lactation and is a useful and well-tolerated treatment for children with severe or intractable cases, but concerns remain regarding its long term side effects.
