In recent years, there have been promising advances in treating rheumatoid arthritis -- especially for those people who do not respond to disease-modifying drugs. The most important advance has been the development of a group of drugs called biologic response modifiers or biologics.

There are several biologics approved to treat rheumatoid arthritis. They include:

• Enbrel
• Humira
• Kineret
• Remicade
• Rituxan
• Orencia

There are also other biologics being studied to treat various forms of arthritis.

How Do Biologics Treat Rheumatoid Arthritis?

Biologics are genetically engineered proteins derived from human genes. They are designed to either inhibit specific components of the immune system that play a pivotal role in either fueling or suppressing inflammation (a key component in several forms of arthritis, such as rheumatoid arthritis and psoriatic arthritis).

What makes these biologics so different from other drugs used to treat rheumatoid arthritis that  modify the immune system is that they affect a specific component of the immune system, not the entire immune system. Thus, these medications theoretically have fewer side effects.

What Are the Side Effects of Biologics?

As with any drugs that suppress the immune system, biologic therapy might pose some risks, since it could make your body more vulnerable to other infections and diseases. Patients should seek immediate medical attention if they develop persistent fever.

Biologics may also cause some chronic diseases in remission -- such as tuberculosis -- to flare up, and they are often not recommended for people with multiple sclerosis and other conditions such as congestive heart failure. All patients should be skin tested for tuberculosis prior to starting biologics.

Since biologic therapy is only in its early stages of use, some of the long-term effects of using these medications simply aren't known, and your doctor will probably want to regularly monitor your health while using them. Biologics are also more expensive than conventional treatments. However, the evidence so far is that they work well and pose fewer risks than other systemic therapies.

One disadvantage to biologic medication is that it has to be given either by injection or by intravenous infusion; the latter approach can take anywhere from 30 minutes to several hours per session. However, the advantages of these drugs are significant.

Although animal studies have shown no effect on fertility or impairment of the fetus, these studies cannot always predict the effects in humans. Accordingly, pregnant women should receive these drugs only if clearly needed.

As a general rule, two biologic therapies should not be taken at the same time.

Researchers say that future agents, still in the early development stages, may be less expensive and will be taken orally. Also on the horizon are biologics that target different chemicals.

Here are some details on each drug:

Enbrel

Enbrel reduces joint inflammation by blocking a chemical called tumor necrosis factor, or TNF.

VitaDocs Medical Reference provided in collaboration with the Cleveland Clinic