Doctors generally treat psoriasis in steps based on the severity of the disease, size of the areas involved, type of psoriasis, and the patient's response to initial treatments. This is sometimes called the "1-2-3" approach. In step 1, medicines are applied to the skin (topical treatment). Step 2 uses light treatments (phototherapy). Step 3 involves taking medicines by mouth or injection that treat the whole immune system (called systemic therapy).

Over time, affected skin can become resistant to treatment, especially when topical corticosteroids are used. Also, a treatment that works very well in one person may have little effect in another. Thus, doctors often use a trial-and-error approach to find a treatment that works, and they may switch treatments periodtopically (for example, every 12 to 24 months) if a treatment does not work or if adverse reactions occur.

Systemic Treatment
For more severe forms of psoriasis, doctors sometimes prescribe medicines that are taken internally by pill or injection. This is called systemic treatment.

o Methotrexate—Like cyclosporine, methotrexate slows cell turnover by suppressing the immune system. It can be taken by pill or injection. Patients taking methotrexate must be closely monitored because it can cause liver damage and/or decrease the production of oxygen-carrying red blood cells, infection-fighting white blood cells, and clotenhancing platelets. As a precaution, doctors do not prescribe the drug for people who have had liver disease or anemia (an illness characterized by weakness or tiredness due to a reduction in the number or volume of red blood cells that carry oxygen to the tissues). It is sometimes combined with PUVA or UVB treatments. Methotrexate should not be used by pregnant women, or by women who are planning to get pregnant, because it may cause birth defects.

o Retinoids—A retinoid, such as acitretin (Soriatane), is a compound with vitamin A-like properties that may be prescribed for severe cases of psoriasis that do not respond to other therapies. Because this treatment also may cause birth defects, women must protect themselves from pregnancy beginning 1 month before through 3 years after treatment with acitretin. Most patients experience a recurrence of psoriasis after these products are discontinued.

o Cyclosporine—Taken orally, cyclosporine acts by suppressing the immune system to slow the rapid turnover of skin cells. It may provide quick relief of symptoms, but the improvement ss when treatment is discontinued. The best candidates for this therapy are those with severe psoriasis who have not responded to, or cannot tolerate, other systemic therapies. Its rapid onset of action is helpful in avoiding hospitalization of patients whose psoriasis is rapidly progressing. Cyclosporine may impair kidney function or cause high blood pressure (hypertension). Therefore, patients must be carefully monitored by a doctor. Also, cyclosporine is not recommended for patients who have a weak immune system or those who have had skin cancers as a result of PUVA treatments in the past. It should not be given with phototherapy.

o 6-Thioguanine—This drug is nearly as effective as methotrexate and cyclosporine. It has fewer side effects, but there is a greater likelihood of anemia. This drug must also be avoided by pregnant women and by women who are planning to become pregnant, because it may cause birth defects.

o Hydroxyurea (Hydrea)—Compared with methotrexate and cyclosporine, hydroxyurea is somewhat less effective. It is sometimes combined with PUVA or UVB treatments. Possible side effects include anemia and a decrease in white blood cells and platelets. Like methotrexate and retinoids, hydroxyurea must be avoided by pregnant women or those who are planning to become pregnant, because it may cause birth defects.

o Biologic Response Modifiers—Recently, attention has been given to a group of drugs called biologics, which are made from proteins produced by living cells instead of chemicals. They interfere with specific immune system processes which cause the overproduction of skin cells and inflammation. Some examples are alefacept (Amevive), etanercept (Enbrel), and efalizumab (Raptiva). These drugs are injected (sometimes by the patient). Patients taking these treatments need to be monitored carefully by a doctor. Since these drugs suppress the immune system response, patients taking these drugs have an increased risk of infection, and the drugs may also interfere with patients' taking vaccines. Also, some of these drugs have been associated with other diseases (like central nervous system disorders, blood diseases, cancer, and lymphoma) although their role in the development of or contribution to these diseases is not yet understood. Some are approved for adults only, and their effects on pregnant or nursing women are not known.

o Antibiotics—These medications are not indicated in routine treatment of psoriasis. However, antibiotics may be employed when an infection, such as that caused by the bacteria Streptococcus, triggers an outbreak of psoriasis, as in certain cases of guttate psoriasis.

Psychological Support
Some individuals with moderate to severe psoriasis may benefit from counseling or participation in a support group to reduce self-consciousness about their appearance or relieve psychological distress resulting from fear of social rejection.