Paracetamol use linked to asthma
Frequent use of paracetamol may make asthma worse, suggests a study
published in Thorax (2000;55:266-70).
Altogether 664 people with asthma and 910 controls, all aged 16-49
years, were questioned about their use of analgesics and the severity
of their symptoms of asthma and rhinitis. Weekly or daily use of
paracetamol (acetaminophen) use was associated with more severe
disease in individuals with asthma or rhinitis, found researchers
from the Guy's, King's and St Thomas' School of Medicine.
Authors warn against switching to aspirin (WILLIAM SHICK/ THE
STOCK MARKET)
Dr Martyn Partridge, chief medical adviser to the National Asthma
Campaign, said: "It is important to highlight that this relationship
is due to frequent (daily and weekly) use of paracetamol, so the
best advice would be to reduce intake." He said that, although not
all people with asthma may be affected, "it confirms the need ...
to exercise caution with paracetamol."
After the media covered the possible link, many people telephoned
the asthma helpline for advice. The researchers recommend that their
results should be taken cautiously, stressing that people should
not switch from using paracetamol to aspirin. They suggest a randomised
trial to establish whether frequent or excessive use of paracetamol
contributes to asthma morbidity in the population.
Many people with asthma avoid aspirin as it is known to trigger
attacks in some individuals. Its use is avoided in children because
it causes Reye's syndrome, and it can cause gastrointestinal bleeding
in adults.
The authors of the study suggest that the worsening of symptoms
is the result of depletion of glutathione. Glutathione is a very
powerful antioxidant; animal studies have shown that paracetamol
administration reduces lung concentrations of glutathione in a dose
dependent fashion. People with asthma produce more reactive species
of oxygen because of the airway inflammation characteristic of the
disease, and they are thus susceptible to any drop in the concentration
of antioxidants. The researchers say that this could cause people
who would otherwise have subclinical disease to have symptoms, as
well as increase the severity of symptoms in those with established
asthma.
Patients were asked about their use of aspirin and paracetamol
and divided into two groups, those with asthma and those without.
The questionnaire also asked about nasal allergies or hayfever,
as well as indicators of the severity of symptoms and socioeconomic
status. After discounting any effects resulting from factors such
as age and smoking status, it was found that increased use of paracetamol
was associated with increasing severity of asthma. The effect was
not apparent with use of aspirin.
Alex Brooks GKT, London
studentBMJ 2000;08:131-174 May ISSN 0966-6494
