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Asthma unlikely to be linked to paracetamol

Association between early use of paracetamol and asthma ‘overstated’

Louise Prime

Wednesday, 26 November 2014

There is no need to alter the policy on using paracetamol in pregnancy and early childhood, say experts today in Archives of Disease in Childhood, because their research* shows that current evidence regarding a link to an increased risk of asthma does not support a change.

Researchers in Australia searched for studies looking at associations between early exposure to paracetamol and the risk of asthma in childhood, and undertook a systematic review and meta-analysis of the 11 suitable studies they found. They looked at whether respiratory infections had been considered as a potential confounding factor by the authors of those studies that reported a link between asthma and paracetamol use.

They found that the seven studies that looked at associations between childhood asthma risk and antenatal paracetamol exposure to paracetamol had come to very different conclusions; and furthermore only one had considered the potential effect of the mother having had respiratory infections during pregnancy.

Six studies examined the effect of having used paracetamol before two years old – when children’s lungs are at a critical stage of development – and consistently concluded that paracetamol increased the risk; however, after they had accounted for the children’s own respiratory infections during infancy, the association was ‘considerably weakened’, say the authors. And although there was an association between the level of asthma risk and the number of times that paracetamol had been used, a history of respiratory infections all but eliminated the link – leading the study’s authors to argue that paracetamol use is unlikely to be a clinically important risk factor for the development of asthma.

They concluded: “The evidence of an association between early life paracetamol and asthma is often overstated, and there is currently insufficient evidence to support changing guidelines in the use of this medicine.” They acknowledged that a placebo-controlled trial is unlikely ever to be conducted, but wrote: “Further well designed clinical trials and/or cohort studies are required to definitely answer this question. Respiratory tract infections appear to confound this association and it is essential that this be accounted for in future observational studies.” They added: “Future studies should also assess the effect of paracetamol exposure on lung function outcomes given that paracetamol is proposed to induce oxidative stress on the airway.”

* M Cheelo, et al. Paracetamol exposure in pregnancy and early childhood and development of childhood asthma: a systematic review and meta-analysis. Archives of Disease in Childhood, Online First, 2014. doi 10.1136/archdischild-2012-303043

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