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Circumstantial evidence suggests a possible connection between the use of acetaminophen and the increasing rate of childhood asthma over the past three decades. However, two UCLA experts caution that there's not enough proof of a link to advise that parents should stop giving the drug to their infants and children. Childhood asthma rates have been on the rise since the 1980s. The increase began about the time parents began switching from aspirin to acetaminophen for their children to lower fevers.
"The link between aspirin and Reye's syndrome in children caused a rethinking that led pediatricians at that time to recommend acetaminophen as the first-line drug for fevers," says Eric Curcio, M.D., a pediatrician at Mattel Children's Hospital UCLA in Santa Monica. While asthma rates started to go up, "it is important to note that many other things were happening at that time, so we can't say for sure, based on that evidence alone, that that's the cause."
Research on the biochemistry of acetaminophen suggests that the drug could contribute to or exacerbate asthma symptoms in some individuals. It can, for example, decrease an antioxidant known as glutathione, and glutathione deficiency can predispose some people to more inflammation of theairways. And studies done more than a decade ago by British researchers indicated that children with asthma were more likely than non-asthmatic children to have used acetaminophen. Other studies since then have reached similar conclusions.
"But these have been observational studies in which the conditions are not controlled," notes UCLA pediatric pulmonologist Sande Okelo, M.D., "You can establish an association, but it might be that people with asthma are simply using acetaminophen more because they have more colds and fevers."
More rigorous studies are necessary to determine whether there is a direct link between acetaminophen use and greater asthma risk, Dr. Okelo says. Other important questions need to be answered as well. For example, if there is a link, how much acetaminophen is necessary to produce the effect? The previous studies suggested that the association between acetaminophen and asthma was most significant in high-frequency users of acetaminophen; it could be, Dr. Okelo notes, that low-frequency users would not be affected.
Another question to be answered: Can use of acetaminophen lead to the development of asthma or does it merely exacerbate symptoms in children with asthma? Until these questions are answered, Dr. Okelo says, "it's too early to make a recommendation for parents not to use acetaminophen."
For parents who are uncomfortable with using acetaminophen for their children, ibuprofen can be an alternative, Drs. Okelo and Curcio say. But parents should note that ibuprofen is generally not recommended for children under six months of age.