TREATMENT FOR PSORIASIS 

Psoriasis is usually a lifelong, relapsing disease in which the main treatment goal is resolution of lesions. The treatment approaches are not curative but can be very effective in controlling the disease. The basic approach­es to therapy involve a reduction in the rate of epidermal proliferation in addition to a decreased dernal inflam­matory and immune response.

An appropriate selection of therapy combined with compliance will usually result in a satisfactory outcome in a few days to a few weeks. The risk-benefit issues are very important when determining a treatment approach as is the recognition of the pathogenic factors involved. The main goal of treatment is to allow the patient to be functional in all aspects of their life and to maintain good physical and emotional health. Patients with limited disease can usually be managed with topical therapy.

The selection of the treatment method is dependent upon a number of factors, including the type of psoriasis, its severity, patient's age and medical history and its location on the body. Generally a trial and error approach is utilized as individuals respond differently to therapy.

Topical therapy can include sunlight, moisturizers, baths, salicylic acid, retinoids, dithranol, coal tar preparations, calcipotriene, tacrolimus and corticosteroids. Sunlight in short, regular daily doses that do not produce a sun burn will clear up psoriasis in some cases. Moisturisers that are thick and greasy, or emollients, aid in hydrating the skin and reducing scaling and itching. They are generally used regularly and over a long time period.

Baths consisting of an oil (generally dispersed with the aid of a surfactant) added to the bath water can be soothing. Generally, the body is soaked for about 15 minutes in water containing a tar preparation, oilated oatmeal or Epsom salts.

Salicylic acid, a keratolytic, aids in removing the scales. It is considered most effective when used in association with topical steroids, coal tar or dithranol. It is generally used in concentrations of 5-10% in ointment or cream vehicles. In cases of thick plaques, a stronger 20% con­centration has been used.

Retinoids used topically, including tazarotene (Tazorac), can be effective. Tazorac is a fast-drying, clear gel that is topically applied. It has few side effects but does not act as quickly as the corticosteroids. Tazarotene, a vitamin A derivative is also very effective for psoriasis. It selec­tively binds to retinoic acid receptors which result in less local irritation and cytotoxicity than other topical retinoids.

Dithranol is an old remedy that is still possibly the most effective of all topical treatments. It works by reducing inflammation and keratinocyte proliferation. It is very effective in treating psoriasis but side effects such as erythema. burning and staining of the skin make it undesirable to patients. Short-contact application of newer anthralin creams can decrease these side effects. Its primary disadvantages are that it is messy and stains the clothing and skin. If it is applied to the skin for only short periods of time (eg 10 to 20 minutes) this minimizes the staining problems. It is often combined with a variety of topical drugs.

Zinc oxide ointment or petrola­tum can first be applied around the lesion followed by the anthralin preparation; this will minimize irritation to the normal skin surrounding the lesion. Dithranol preparations are generally applied in concentrations from 0.05% to 5% and is applied at night. Wearing plastic gloves and using old sheets and nightclothes will help to minimize its staining properties.

Coal tar preparations (the oldest treatment for psoriasis), described by the Greek philosopher Dioscorides nearly 2;000 years ago, are effective in treating psoriasis. Coal tar can contain up to 10,000 different chemical compounds and its precise mechanism of action is unknown. Coal tar has antiproliferative and anti-inflammatory actions and it has been demonstrated to be efficacious in the treatment of mild to moderate psoriasis. It can be used alone or in combination with other drugs and phototherapy (UVB).

The use of coal tar preparations is limited by their main disadvantages; they are messy and smelly to use. Many of the newer purified tars in more elegant creams, ointments and gels are easier and more pleasant to use. Coal tar preparations seem to increase the effectiveness of UV light. They generally are applied at bedtime with sufficient time allowed for drying and then removed by showering in the morning. As an alternative, they can be applied in the morning, allowed to stay for 10-15 minutes. and then showered off.

Calcipotriene is a synthetic form of vitamin D3. Calcipotriene ointment (Dovonex) can control the excessive production of skin cells when used twice daily. It's use may be based on the observation that hypocalcemia is present in many patients who develop various forms of psoriasis. It can irritate the skin and is not recommended for the face or groin area. About 60% of the patients have a good to excellent response after 4 months of treatment.

Corticosteroids are the choice of many physicians to begin therapy. The corticosteroid creams or ointments are easy to use and are a good choice for the scalp, Face, ears and skin folds. However, these should not be used for too long a time period. The adverse effects and mechanism of actions vary greatly between the available topical agents. Chronic use of topical steroids can result in decreased effectiveness, local tissue atrophy and sys­temic glucocorticoid effects. Therefore, topical steroids should only be instituted as an adjunct to therapy if long-term use is required.

Phototherapy involves ultraviolet light; some of the artificial sources of UVB light are similar to natural sunlight. There are some newer phototherapy light sources available, called narrow-band UVB, that emit the part of the UV spectrum that is most beneficial for psoriasis. Generally, phototherapy is used after topical treatments, even though some physicians actually start with phototherapy. 

Combination phototherapy can involve the use of psoralen and ultraviolet A light (PUV A). Psoralen serves to enhance the sensitivity of the body to this light and is used when more than 10% of the skin is affected or whenever a quick response is required as when the disease is interfering with an individual's occupation. PUV A treatments two or three times weekly appear to be more reliable in clearing psoriasis than UVB treatments; however, they are associated with increased short-term side effects, including nausea, headache, fatigue, burning and itching.

If topical therapies fail or the disease is severe, systemic treatment can be instituted. Some common systemic therapies include methotrexate, acitretin. cyclosporin, hydroxyurea and antibiotics.

Methotrexate, which may work through immunomodulation, is effective for severe disease but is limited by its severe side effects and possible mutagenic effects. These patients must be closely monitored and methotrexate should not be used in patients with long-term liver disease or anaemia.

Acitretin, a systemic retinoid is useful in erythrodermic, chronic, and pustular psoriasis. The main concerns with this medication are teratogenicity and hyperlipidemia. Careful patient selection and laboratory monitoring increase the safety of acitretin.

Cyclosporin is an immune suppressant that slows rapid cell growth. It provides rapid symptomatic relief but is effective only as long as the treatment lasts. Patients with severe pso­riasis or those that are refractory to other systemic therapies are generally the best candidates for cyclosporin. Side effects such as hypertension and renal toxicity may limit its use.

Hydroxyurea is not as toxic as methotrexate and cyslosporine but it is also not as effective. It can be combined with PUV A or UVB. Side effects include anaemia and a decrease in white blood cell and platelet counts.

Antibiotics are not routine treatment for psoriasis but can be prescribed whenever an infection triggers the outbreak of the disease.