If you have moderate to severe psoriasis, your doctor may suggest "systemic drugs" -- medicines that affect your entire body. They're typically used when psoriasis covers more than 5% to 10% of your body and you haven't seen improvement from other methods, like phototherapy and treatments you apply to your skin, such as creams, ointments, solutions, and foams.
While systemic treatment can help, many of the drugs can cause serious side effects. Your doctor will want to monitor you closely.
Methotrexate. This drug eases psoriasis symptoms by curbing the immune system (your body's defense system against germs) and stopping the rapid growth of your skin cells.
You take this medicine either by mouth or by an injection. Usually, you take it once a week and see results after 4 to 6 weeks.
Methotrexate can have serious side effects. At first, you might have nausea or fatigue. Over time, methotrexate can damage the liver and blood cells.
Make sure to tell your doctor about any other conditions you have, since methotrexate is not safe for people with anemia or liver disease. You should also limit how much alcohol you drink. Even one glass a day while you're on the drug may cause liver problems.
Women who are pregnant or thinking about becoming pregnant should not take this drug. Their male partners should also avoid it.
While taking methotrexate, you'll need to get regular blood tests to monitor your blood cells and liver function.
Cyclosporine. Like methotrexate, this drug curbs your immune system and slows the growth of your skin cells. It's typically used only in severe cases of psoriasis, when nothing else seems to work.
You take cyclosporine by mouth. While it can help clear psoriasis, its benefits typically last only for as long as you're using it.
Cyclosporine also carries risks. It can cause kidney problems, high blood pressure, and high cholesterol. If you have a weak immune system or you're breastfeeding, you shouldn't take it. You also shouldn't use it if you're treating your psoriasis with PUVA therapy, a form of phototherapy. Because of the potential side effects, experts recommend that you not take the drug for more than a year at a time.