A study published earlier this month in Pediatrics finds a strong association between the use of acetaminophen and asthma, both in symptoms and number of cases, for children and adults.
John McBride, Director of the Respiratory Center at Akron Children's Hospital, reviewed studies going back more than a decade, one of which looked at 300,000 children around the world. "Looking at the data," he said, "it's quite likely that acetaminophen is a problem for patients that have asthma."
The association between asthma and acetaminophen, which many people know by the brand name, Tylenol, caught him by surprise, he says. "I read the literature and was stunned. I decided the people who really needed to know were primary are physicians and patients."
Among the most compelling studies was one done in 2000 at Boston University. Ironically, it was a follow up to research that had established the safety of ibuprofen.
The ibuprofen study followed 84,000 children with a fever who were randomly treated with either ibuprofen or acetaminophen. In 2000, researchers looked at the 1800 children who had previously been diagnosed with asthma. "The children who took acetaminophen were twice as likely to be seen for an asthma attack than kids who got ibuprofen, and the more acetaminophen they took, the more likely they were to be seen for an asthma attack," McBride learned.
But an association between acetaminophen and asthma is different from showing that acetaminophen causes an asthma episode. Dr. David Cornfield, Chief of Pediatric Pulmonary Medicine at Stanford's Lucile Packard Children's Hospital agrees that an association exists. "What's really needed now," he says, "is a trial that would establish causation. To do that, you have to have a well-powered placebo controlled trial, several years long."
The Boston University study was a great starting point, says Dr. Maria Garcia-Lloret, Professor of Pediatric Allergy at Mattel Children's Hospital at UCLA. But the majority of the children in the study were caucasian. In addition, she says, a new study should include a control group, that receives placebo. "This is a study that could be repeated as a prospective, randomized study, with a broader population, with a different genetic makeup. The kids in this study were 77% white. Blacks, in particular, are more prone to more severe asthma, more severe allergies."
Doctors point to a couple theories as to why acetaminophen may be problematic for people with asthma. Acetaminophen has "long been shown to diminish the response of the immune system to viruses," Dr. Cornfield explained, specifically two molecules which help the lungs defend against viruses.
Johnson & Johnson, maker of Tylenol, provided a statement today stating, "Tylenol (acetaminophen) has over 50 years of clinical history to support its safety and efficacy and, when used as directed, Tylenol, has a superior safety profile, compared with other OTC [over the counter] pain relievers."
But Dr. McBride questions the safety of acetaminophen for people with asthma. He agrees more thorough research is needed, but for a different reason. He closes his study:
At present, however, I need further studies not to prove that acetaminophen is dangerous but, rather, to prove that it is safe. Until such evidence is forthcoming, I will recommend avoidance of acetaminophen by all children with asthma or those at risk for asthma and will work to make patients, parents, and primary care providers aware of the possibility that acetaminophen is detrimental to children with asthma.
In the meantime, every doctor we contacted reminded us that over-the-counter medicines are still medicines, with side effects. "You have to think twice before you give yourself or your child a medicine," says Dr. Garcia-Lloret. "Do they really need it? Or will they get better on their own? You have to balance whether it’s necessary or whether you can wait a bit and it will resolve by itself."