BEIJING, Aug. 5 (Xinhuanet) -- Blockbuster prescription drugs used to treat rheumatoid arthritis and other autoimmune conditions can raise the risk of potentially deadly cancer in children and teenagers, media quoted the Food and Drug Administration (FDA) as saying on Wednesday.

    The FDA ordered stronger warnings on such medications. An analysis of 48 reported cancer cases in children using the drugs "showed an increased risk of cancer, occurring after 30 months of treatment on average," the agency said. Eleven of the reported cases were fatal.

    After more than a year of review, FDA scientists said the group of best-selling drugs used to treat arthritis and other inflammatory diseases appear to increase the risk of lymphoma after they are used beyond two and half years.

    The drugs are known as tumor necrosis factor (TNF) blockers and work by neutralizing a protein that, when overproduced, causes inflammation and damage to bones, cartilage and other tissue.

    In children, the drugs are mainly prescribed to treat rheumatoid arthritis, inflammatory bowel disorder and Crohn's disease. More broadly, they are approved to treat a variety of chronic, inflammatory and autoimmune system diseases including juvenile idiopathic arthritis, rheumatoid arthritis, psoriatic arthritis, plaque psoriasis and ankylosing spondylitis.

    The agency will bolster the "black box" warning on the five drugs sold in the U.S., including Abbott Laboratories' Humira, Johnson & Johnson's Remicade and Simponi, and Enbrel, which is co-marketed by Amgen Inc. and Wyeth.

    (Agencies)