Treatment for psoriasis ranges from topical applications, including steroids, tazarotene, acetylenic retinoids, and salicylic acid, to phototherapy using UVB and PUVA light therapy, or the use of medications such as methotrexate or cyclosporine.
PUVA Therapy; Methoxsalen, Psoralen
Clinical studies have shown that PUVA therapy, which uses ultraviolet A radiation plus oral methoxsalen, is known to increase the incidence of melanoma. Topical forms of psoralen, a photosensitizing drug derived from plant sources, were shown to be effective to treat psoriasis. Psoralen is commonly taken orally in conjunction with UVA light therapy, which had been associated with an increased risk of non-melanoma skin cancer.
Coal Tar, UVB Radiation
When treating patients with severe psoriasis, the use of coal tar along with increased UVB radiation has been a common form of therapy when treating psoriasis. This therapy requires an average of 20 to 30 treatments, gradually increasing doses of ultraviolet B radiation together with topical application of coal tar. Therapy maintenance consists of lowering the dose of UVB radiation once a week, unless relapse occurs, in which case the treatment frequency must be increased. Both coal tar and UVB radiation therapy have carcinogenic effects.
Methotrexate is metabolized from aminoptenin, and is derived from a class of drugs called anti-metabolites. When used on patients with arthritis, methotrexate was shown to result in clearing of psoriatic plaques. Methotrexate is now approved by the FDA for use in severe psoriasis, as well as rheumatoid arthritis and certain cancers. Although the exact mechanism of action of methotrexate in psoriasis is unknown, it was the first effective systemic medication used in the treatment of psoriasis, and continues to be the standard of therapy against which other therapies are compared.
Methotrexate is used in patients with extensive psoriasis that does not respond to topical therapy. When the cumulative dose of methotrexate reaches 1500 mg, patients should be monitored having liver biopsies. Psoriasis patients have an increased risk of developing liver fibrosis and cirrhosis from treatment with methotrexate compared to patients with rheumatoid arthritis treated with similar doses. Side effects may include nausea or diarrhea, and severe hematologic effects decreasing blood cell counts can occur in 25% of patients.
Systemic cytotoxic drugs such as Azathioprine, has been used for treatment of severe psoriasis. However, its use for psoriasis has been limited due to the fact that it causes severe depression of blood formation by the bone marrow and is also associated with an increased risk of malignancies such as lymphoma or squamous cell carcinoma. Thioguanine, a metabolite of Azathioprine, has been shown to cause cell death of activated T lymphocytes. The depletion of activated T lymphocytes from psoriatic plaques resulted in clearing of psoriasis lesions. Thioguanine appears to be successful in patients who could not continue Methotrexate therapy due to liver damage, however, side effects of bone marrow suppression has occurred.
Cyclosporine was found to reduce the number of T lymphocytes in psoriatic lesions, thereby leading to a significant remission of psoriasis lesions. Cyclosporine is indicated in patients who have failed to respond to at least one systemic therapy, or who cannot tolerate other systemic therapies. Cyclosporine therapy has proved remarkably effective with long term administration, although most patients relapsed within 8 to 12 weeks after discontinuation of use, and required higher doses to achieve sufficient improvement. Side effects may include hypertension and renal dysfunction. Other side effects include the incidence of cancer, and are similar to that of Methotrexate, with about 1% of patients developing malignancies, of which 50% are skin cancers.
Vitamin D Analogue; Calcipotrol
Calcipotrol is a topical Vitamin D analogue used to treat psoriasis. When Calcipotrol is used after PUVA or UVB therapy, a lower dose of radiation may be needed. Side effects include mild irritation, and hypercalcemia may occur if recommended doses are exceeded.
Vitamin A Therapy; Systemic Retinoids
Systemic retinoids can enhance the effects of many other topical and systemic therapies, and are often used in association with topical agents and phototherapy. Oral therapies for psoriasis include those derived from Vitamin A such as Etretinate and Acitretin. Etretinate proved most effective compared to Acitretin for treatment of pustular psoriasis, but has teratogenic (birth defects) potential, and can be found stored in fatty tissue up to two years after use.
Acitretin, a metabolite of Etretinate, is less lipophilic, and is cleared from the body more rapidly than Etretinate, which is considered to pose less teratogenic effects. Acitretin has been approved by the FDA for treatment of psoriasis, although it is less effective than Etretinate, which it has replaced. Long term therapy using systemic retinoids such as Etretinate and Acitretin, requires periodic monitoring for skeletal toxicity.
Topical Retinoids; Tazarotene
A topical retinoid, Tazarotene, was recently introduced for the treatment of psoriasis, which can irritate normal skin, causing pruritis and erythema. Patients who had a successful response to topical therapy, relapsed within three months of discontinuation in 37% of patients. Topical retinoids such as Tazarotene may be enhanced when combined with ultraviolet radiation therapy.
Corticosteroids are steroid hormones naturally found in the body that are involved in stress response, immune response, and regulation of inflammation. Physicians may prescribe corticosteroids to help control inflammation by decreasing levels of pro-inflammatory interleukins in the body, but it is important to know that there are side effects with long term use.
It has been found that corticosteroid therapy may only have temporary affects with some patients. Psoriasis plaques have been known to reappear when patients stopped corticosteroid therapy. Long term therapy with topical steroids can cause thinning of the skin, striae, skin discolorations, masking of local infections, and hypopigmentation.
Photodynamic therapy using the topical prodrug Levulan, also know as aminolevulinic acid, is a safe alternative to prescription drugs. Other therapies include topicals that contain salicylic acid such as Miraderm, was shown to clear psoriasis lesions within three months after topical application.
Linda Gulla offers CME and CEU, bringing medical aesthetics to the licensed professional. She can be reached at firstname.lastname@example.org.