Acetaminophen May Be Linked to Asthma Risk
Study Shows Painkiller Raises Risk of Asthma; Manufacturer Says Drug Is Safe
By
Kathleen Doheny
WebMD Health News
Reviewed By
Louise Chang, MD
Nov. 5, 2009 -- The popular pain and fever reliever acetaminophen may be
linked with an increased risk of asthma in children and adults, according to a
new research review of previously published studies by Canadian
researchers.
But the manufacturer of Tylenol -- the brand-name version of acetaminophen
-- says the painkiller has a well-established safety record.
Researchers pooled the results of 19 clinical studies, with a total of more
than 425,000 participants, to see if the association between the pain reliever
use and asthma (and wheezing in children) held up. It did.
What triggered the review? "Concern over the risk of acetaminophen and
asthma highlighted by the 2008 ISAAC study, published in The Lancet,"
says the review's lead author Mahyar Etminan, PharmD, a scientist at the
Vancouver Coastal Health Research Institute in British Columbia and an
assistant professor of medicine at the University of British Columbia.
In the ISAAC (International Study of Asthma and Allergies in Childhood)
study, researchers looked at more than 205,000 children, ages 6 to 7, in 31
countries and found that acetaminophen use for fever in the first year of life
was linked to increased risk of asthma symptoms in children 6 to 7 years old.
Current use of acetaminophen was also linked to increased risk of asthma
symptoms.
Other studies, Etminan says, have produced conflicting results, so the
Canadian team conducted the review.
Sales of acetaminophen products in the U.S. are about $1 billion annually,
the researchers estimate.
Calculating Asthma Risk
Etminan's team searched the medical literature to find high-quality
published studies, trying to quantify the risk of asthma and wheezing among
acetaminophen users, as well as the effect of prenatal exposure to the
medicine.
After eliminating studies that weren't scientifically sound enough, the
researchers focused on 19 studies. Overall, they found that acetaminophen users
were 63% more likely to have asthma than nonusers. Other findings:
- The risk of asthma in children given acetaminophen in the year before their
asthma diagnosis was increased by 60%.
- The risk of asthma in children who used acetaminophen in the first year of
life was 47% higher than in those who didn't use it.
- The risk of asthma in adults who used acetaminophen was 74% higher than in
those who did not.
- Prenatal use of acetaminophen boosted the risk of wheezing by 50% and the
risk of asthma by 28% in children.
The researchers concede that children with severe asthma may be more likely
to get acetaminophen for viral or other infections that may actually be due to
asthma or may precede an asthma diagnosis.
The finding of acetaminophen use and asthma is an association, they say, but
not necessarily a cause and effect.
The researchers say other mechanisms may explain the link. Acetaminophen,
they say, may boost an enzyme involved in the anti-inflammatory response in
asthma.
There are other possible mechanisms. "There isn't enough evidence to favor
one over the other," Etminan says. He says more studies are needed to fully
understand the association.
Drugmaker's Perspective
In a prepared statement, McNeil Consumer Healthcare, which makes Tylenol,
says:
"TYLENOLŪ (acetaminophen) has over 50 years of clinical history to support
its safety and efficacy and, when used as labeled, TYLENOLŪ has a superior
safety profile compared with many other over-the-counter (OTC) pain
relievers. The well-documented safety profile for acetaminophen makes it
the preferred pain reliever for asthma sufferers."
The statement continues: "There are no prospective, randomized controlled
studies that show a causal link between acetaminophen and asthma. The
systematic review and meta-analysis published in Chest does not
establish a definitive casual relationship between the therapeutic use of
acetaminophen and an increased risk of asthma and wheezing in both children and
adults. In fact, the study investigators admit that their systematic review is
subject to several limitations, one of which is that diagnosis of asthma in
most of the studies was through self-reporting and the possibility of
misclassification of asthma with other respiratory conditions can't be
excluded. The authors also stated that additional studies would be needed in
order to verify their findings."
Second Opinion
Another expert said the review is strong. "This is clearly synthesizing the
studies that have been conducted over the past 10 years and is showing the
emerging evidence that acetaminophen seems to be associated with the
development of asthma and asthma-like symptoms in children and adults," says
Matt Perzanowski, PhD, assistant professor of environmental health sciences at
the Mailman School of Public Health at Columbia University in New York.
With his colleagues at Columbia, Perzanowski recently found that prenatal
acetaminophen exposure boosts the risk of wheezing in inner city, minority
children (who have high rates of asthma) at age 5.
They believe that children with a genetic mutation affecting an antioxidant
that helps "detox" the body may be the ones at risk, Perzanowski tells
WebMD.
A practicing allergist, Rebecca G. Piltch, MD, who cares for patients with
asthma and allergies in Marin County, Calif., says the association is
interesting but points out it does not prove cause and effect.
Perzanowski agrees, saying: "There is still a possibility the association is
due to some other mechanism besides the acetaminophen."
Until more research is done, what's a parent or adult to do? "The American
Academy of Pediatrics recommends acetaminophen as the drug of choice for
controlling fever," Etminan says. "Parents should still follow these guidelines
until the recommendations change."
"For adults, ibuprofen is an alternative drug that can be used," he says.
"Unlike acetaminophen, ibuprofen has not been shown to be associated with
asthma."
Following the recommended dose is important, he says. The question of
whether a specific dose is linked with the risk of asthma needs to be studied,
Etminan says.
Patients already diagnosed with asthma should check with their own doctor
about acetaminophen use, Piltch says. Those who don't have asthma "but have
concerns about acetaminophen should discuss them with their primary care
provider."
SOURCES: Mahyar Etminan, PharmD, scientist, Center for Clinical Epidemiology and Evaluation, Vancouver Coastal Health Research Institute; assistant professor of
medicine, University of British Columbia, Canada.
Etminan, M. Chest, November, 2009; vol 135: pp 1316-1323.
Beasley, R. The Lancet, Sept. 20, 2008; vol 372: pp 1039-1048.
Perzanowski, M. Thorax, published online Oct. 22, 2009.
Matt Perzanowski, PhD, assistant professor of environmental health sciences, Mailman School of Public Health, Columbia University.
Rebecca G. Piltch, MD, allergist and immunologist, Marin County, Calif.
Marc Boston, McNeil Consumer Healthcare.
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