(Ivanhoe Newswire) -- Medications frequently used to treat rheumatoid arthritis appear to be associated with an increased risk for herpes zoster, a painful infection also known as shingles that is characterized by blisters, according to a new study.

Some previous studies have suggested that patients treated with anti-tumor necrosis factor a (TNF-a) antibodies are at an increased risk for bacterial infections, but little is known about the risk of viral infections, such as herpes zoster, in rheumatoid arthritis patients.

Researchers said herpes zoster is one of the most common side effects reported in clinical trials involving anti-TNF-a agents, and patients with rheumatoid arthritis are at increased risk of herpes zoster compared with the general population.

For this study, researchers investigated the association of various rheumatoid arthritis treatments with the risk of developing herpes zoster. A total of 5,040 patients were monitored for treatment, clinical status and adverse reactions for use to three years.

Researchers found that there were 86 cases of herpes zoster reported among 82 patients. Those cases were split among several different anti-TNF-a antibodies. Researchers also discovered that older patients and those treated with glucocorticoids -- steroid hormones that are widely used as anti-inflammatory medications -- experienced a significantly higher risk of developing the infection.

The authors urged doctors to closely monitor patients treated with monoclonal anti-TNF-a antibodies for early signs and symptoms of herpes zoster.

SOURCE: Journal of the American Medical Association, 2009;301:774-775