Acetaminophen May Be Linked to Asthma Risk
Study Shows Painkiller Raises Risk of Asthma; Manufacturer Says Drug Is Safe
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
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
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
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
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.