Regular use of the painkiller acetaminophen, also known as paracetamol, is associated with higher rates of asthma and chronic obstructive pulmonary disease (COPD) and reduced lung function, according to a new study.

Animal experiments have suggested that acetaminophen might lower antioxidant activity in the lungs, explain Dr. Tricia M. McKeever, at City Hospital in Nottingham, UK, and her associates in the American Journal of Respiratory and Critical Care Medicine.

Whether this experimental evidence translates to an effect on human respiratory disease has been unclear. The team therefore evaluated data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted between 1988 and 1994 in the US.

Among the 13,492 subjects in the study, 6.9 percent had asthma, 11.8 percent had COPD and 2.8 percent had both respiratory illnesses.

Overall, 4.3 percent of the participants reported that they used acetaminophen daily. Another 8.2 percent and 2.5 percent, respectively, reported daily use of aspirin and ibuprofen.

The use of acetaminophen was associated with an increased risk of both asthma and COPD, and the risk increased in step with the dose.

Lung function was also lower among those using acetaminophen daily.

In contrast, taking aspirin or ibuprofen was not associated with respiratory illness.

This does not necessarily mean that acetaminophen should be avoided, however. "The potential risk of acetaminophen must ultimately be estimated through a balance consideration of the positive benefit and the potential harm if these medications were substituted with others," McKeever's group advises.

SOURCE: American Journal of Respiratory and Critical Care Medicine, May 2005.