( Health.com ) -- A class of injectable drugs used to treat autoimmune disorders such as rheumatoid arthritis does n't raise the risk of serious infection when compared with more conventional treatments , according to a new analysis in the Journal of the American Medical Association . The research , which was funded by the Food and Drug Administration and other federal health agencies , contradicts numerous earlier studies that did find an increased risk of infection associated with the drugs , known as tumor necrosis factor ( TNF ) inhibitors . The possibility that TNF inhibitors -- which include popular drugs such as Humira and Enbrel -- pose no additional infection risk is a `` very new and heretical idea , '' says David T. Felson , M.D. , a professor of medicine and epidemiology at the Boston University School of Medicine , who cowrote an editorial accompanying the study . `` Up until now there has been considerable evidence that anti-TNFs heightened the risk of serious infection compared to other treatments . '' Health.com : Signs and symptoms of rheumatoid arthritis . The lead author of the study , Carlos G. Grijalva , M.D. , a professor of preventive medicine at Vanderbilt University , in Nashville , Tennessee , says the findings `` should be reassuring for patients and providers . '' Felson , however , says the new findings are n't sufficient to quell the concerns raised by previous studies . `` We still need to be concerned about serious infection risk among patients starting these medicines , '' he says . Autoimmune conditions , including rheumatoid arthritis , psoriasis , and inflammatory bowel disease , arise when the body 's immune system goes awry and begins attacking healthy cells and tissue . TNF inhibitors -- known as biologic drugs , because they 're derived from substances that occur naturally in humans and animals -- work by blocking the action of TNF , an important immune-system molecule . Health.com : 10 risk factors for inflammatory bowel disease . This class of drugs drastically improved the treatment of these conditions when first introduced in the late 1990s , but because they suppress the immune system they are believed to open the door to opportunistic infections . Some patients taking the drugs have died from these infections , and the FDA has been closely watching the drugs ' safety profile as more and more people use them . Previous studies have found that TNF inhibitors as much as double the risk of serious infection compared with other treatment options . Those trials tended to be relatively small , however . The new study , which was presented this weekend at an annual meeting of the American College of Rheumatology , sought to address that weakness . Grijalva and his colleagues combined data on more than 32,000 mostly low-income people from four large health-care databases , including those for Medicaid and Medicare . About half of the people took TNF-inhibitors for their conditions , and the other half took older , non-biologic drugs -- such as leflunomide , hydroxychloroquine , and sulfasalazine . Health.com : Got psoriasis ? 7 signs you may have arthritis too . The authors identified 1,172 infections requiring hospitalization during the study period . ( The most common infections were pneumonia and skin and soft-tissue infections . ) After one year of treatment , people taking TNF inhibitors had no higher risk of serious infections than those taking other types of drugs . The researchers did find , however , that among patients with rheumatoid arthritis , the TNF inhibitor Remicade carried an approximately 25 % higher risk of infection than Enbrel or Humira . How well are you managing your rheumatoid arthritis ? Take a health test . It 's not clear why Remicade might be riskier than other TNF inhibitors , but it 's possible that the higher initial doses the drug requires might be partly responsible , Grijalva says . The mechanism of action may also be slightly different than that of other TNF inhibitors , he adds . The study does have an important limitation that detracts from the findings , Felson says . As he notes in his editorial , some 40 % of participants taking TNF inhibitors dropped out within the first month , compared with only 15 % in the comparison group . In previous trials and in clinical practice , people who stop taking TNF blockers `` tend to be older and at a higher risk of serious infections , '' Felson says . That pattern , he adds , may have skewed the study results and made TNF inhibitors look safer than they perhaps really are . Copyright Health Magazine 2011 .
The research follows numerous earlier studies that did find an increased risk . Felson , however , says the new findings are n't sufficient to quell the trend . Previous studies have found that drug inhibitors as much as double the risk .