The FDA has approved two new uses for the arthritis drug Humira.

The drug, which was previously approved to treat rheumatoid arthritis in 2002, is now also approved to treat psoriatic arthritis, a form of arthritis that arises in people with the skin condition psoriasis.

The FDA also broadened Humira's use in rheumatoid arthritis to include people recently diagnosed with the disease.

Humira is delivered via an injection under the skin and works by blocking an inflammation-causing protein called tumor necrosis factor alpha, or TNF-alpha. This protein is released by the body's immune system and causes joint swelling and damage.

Humira Approved for Psoriatic Arthritis

Psoriatic arthritis causes pain and swelling in the joints as well as dry, scaly skin.

The FDA based its approval of Humira for psoriatic arthritis on a clinical trial involving 313 people with moderate to severe forms of the disease that were not successfully treated with anti-inflammatory medications, such as NSAIDs (nonsteroidal anti-inflammatory drugs).

After 24 weeks of treatment, people who received Humira experienced significantly greater improvement in skin and joint symptoms than those who took a placebo.

The recommended dose of Humira in treating psoriatic arthritis is 40 milligrams every other week delivered via a shot under the skin.

Humira Approved for Early Rheumatoid Arthritis

The FDA also approved Humira as a first-line treatment for people with moderate to severe rheumatoid arthritis (RA). Previously, it was approved for use after other drug treatments for RA failed.

The expanded approval was based on a study of nearly 800 people with moderate to severe RA that had not been previously treated with methotrexate.

The results showed that treatment with Humira in combination with another drug methotrexate provided more symptom relief and prevented further joint damage better than treatment with methotrexate alone.

Side effects of Humira include irritation at the injection site, headache, and hypertension. Using Humira can also lead to an increased vulnerability to infection.

A new warning was added to Humira's label in 2004 detailing the risks of rare but potentially serious allergic reactions, blood cell deficiencies, and drug interactions associated with use of the drug.