There has been concern that these medications, called anti-tumour necrosis factor (anti-TNF) drugs, might increase the chances of a shingles infection (also known as herpes zoster) because they work by suppressing a part of the immune system that causes the auto-immune attack.
"These are commonly used drugs for people with rheumatoid arthritis and other auto-immune diseases, and the issue was whether or not they increased the risk of [shingles]. We found there is no increased risk when using these drugs, which was reassuring," said study author Dr Kevin Winthrop, associate professor of infectious disease and public health and preventive medicine at Oregon Health and Science University in Portland.
Shingles is a major concern for people with auto-immune conditions, particularly people who are older and more at risk for developing shingles in general. Shingles is caused when the same virus that causes chickenpox is reactivated.
The symptoms of shingles, however, are often far more serious than chickenpox. It typically starts with a burning or tingling pain, which is followed by the appearance of fluid-filled blisters, according to the US National Institutes of Neurological Disorders and Stroke. Shingles pain can vary from mild to so severe that even the lightest touch causes intense pain.
People who have rheumatoid arthritis already have an increased risk of shingles, although Winthrop said it's not exactly clear why. It may be due to older age, or it may have something to do with the disease itself.
Rheumatoid arthritis and other auto-immune conditions are treated with many different medications that help dampen the immune system and, hopefully, the auto-immune attack. Corticosteroids such as prednisone often are the first line of treatment, but because these drugs have many side effects, the goal is to be on the lowest dose possible or off them altogether.
Two other classes of drugs - the "biologic" anti-TNF drugs and a group of medications called non-biologic disease-modifying anti-rheumatic drugs (DMARDs) - are newer medications that can be used to treat rheumatoid arthritis and other auto-immune conditions. Examples of biologics are adalimumab (Humira), etanercept (Enbrel) and infliximab (Remicade). A commonly used DMARD is methotrexate.
Vaccine before medication
Winthrop and his colleagues reviewed data from almost 60 000 people with various auto-immune conditions, such as rheumatoid arthritis, inflammatory bowel disease, psoriasis, psoriatic arthritis and ankylosing spondylitis. More than 33 000 were taking biologic anti-TNF drugs, and almost 26 000 were on DMARDs. The study period ran from 1998 through 2008.
They found no significant increase in the risk of shingles based on the type of medicine people were taking, with the exception of a high dose of corticosteroids. People taking more than 10 milligrammes a day of corticosteroid medication had twice the odds of developing shingles.
Dr Patience White, vice president of public health for the Arthritis Foundation, said the study's findings were good news.
"People worry a lot about taking drugs, and this well-done study says this is another thing we don't have to worry about," said White, who also is a professor of medicine and paediatrics at the George Washington University School of Medicine and Health Sciences, in Washington, DC.
"Drug therapies, other than corticosteroids, don't increase the risk of getting [shingles]."
Both White and Winthrop said people, if possible, should get the shingles vaccine before they start taking medication for an auto-immune condition. The shingles vaccine is a live vaccine, so it's not recommended for people who are on any type of immune-system-altering drug.
Winthrop said that based on the latest findings, he suspects it would be OK to vaccinate people on the newer medications, but he added that a study would need to be done first to confirm that.
Learn more about anti-TNF medications from the American College of Rheumatology.
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