Tylenol, an asthma risk?

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Acetaminophen — also known commercially as Tylenol or Paracetamol — has been linked with increase asthma rates. A new review now considers the associations between asthma and acetaminophen strong enough to call for a complete stop to use of acetaminophen for children with, or at risk of, asthma.

“Until future studies document the safety of this drug,” argues John McBride, a pediatric lung specialist and director of the Respiratory Centre at Akron Children’s Hospital in Ohio. “Children with asthma, or at risk of asthma should avoid the use of acetaminophen.”

Asthma affects 23 million people in the United States. McBride considers that not only that acetaminophen might exacerbate asthma, but that it may also be a cause of asthma.

These associations have important implications for African-Americans. There is an estimated 62 percent higher prevalence of asthma among African-American children compared to white children.

Nearly 13 percent of African-American children and around 8 percent of white American children are thought to suffer from asthma. African-American children, therefore, may be at an increased risk of asthma from acetaminophen use.

The consequences of asthma are also likely to be worse for African-American children; they are 2.5 more likely to be hospitalized for asthma and five times higher risk of death than white children.

In addition to advising restricted use of acetaminophen for children with, or at risk of asthma, studies have also advised cautious use of acetaminophen during pregnancy.
Research from Columbia University’s Center for Children’s Environmental Health showed that the children of women who took acetaminophen during pregnancy were more likely to have children with persistent asthma symptoms at 5 years of age.

The study also found a stronger asthma and acetaminophen association for children with a particular genetic variant in an enzyme that detoxifies foreign substances in the body. These specific genetic variants of this enzyme, glutathione S-transferase, are more frequently found in African-American and Hispanic populations than in other ethnic groups.

In addition to the higher asthma burden for African-American children, associations between asthma, acetaminophen and sickle cell disease — which affect around 1 in 350 African-Americans — are also reported.

McBride says the existing data accumulated is strong enough to make a clear decision about the use of acetaminophen. McBride comes squarely to the conclusion that use of acetaminophen is unsafe for children with asthma.

“I will recommend avoidance of acetaminophen by all children with asthma and will work to make patients, parents and primary care providers aware that acetaminophen is detrimental to children with asthma,” McBride asserts.

In support of his recommendation, McBride cites the large International Study of Allergy and Asthma in Childhood that involved enrollment of children at 122 study sites in 54 countries. From data for 200,000 children who were aged six to seven years, analysis showed that children were over three times more likely to develop asthma if they took acetaminophen once a month.

McBride also cites further research that compiled and analyzed the results of multiple studies to include nearly 27,000 children. This research showed an increased two-fold risk of asthma for children using acetaminophen.

Another similar compilation analysis examined the results of multiple adult studies to show that adults who used acetaminophen were also nearly twice as likely to experience asthma compared to those who didn’t.

“A growing number of studies have documented such a strong association between acetaminophen exposure and asthma,” McBride explained, “that much of the dramatic increase in childhood asthma over the past 30 years has been related to the use of acetaminophen.”

Showing associations does not prove that acetaminophen causes asthma, although much of the accumulated evidence is robust. Reports that provide substance to the association go back over decades, but there are also reservations around association studies as no clear molecular or immune pathways have yet been identified to prove this connection.

McBride also admits that there may be other unrelated factors which could explain some or all of the association between acetaminophen and asthma. However, based on the available evidence, he remains certain of his conclusion.

“I need further studies not to prove that acetaminophen is dangerous but, rather, to prove that it is safe,” McBride said.