Pain relievers and children with asthma

Aspirin is contra-indicated in children or adolescents under 16 years of age with febrile illness, not because of concerns about associated bronchospasm, but because of the association with Reye’s syndrome (an acute illness producing inflammation of the brain and liver).¹ A decline in the incidence of Reye’s syndrome has occurred since warnings were first issued about the possible role of aspirin in this syndrome.^{11<LE III-2>}

Paracetamol can also be associated with bronchospasm in children with asthma. The effect appears to be dose-dependent, with the greatest risk observed for doses greater than 1500 mg of paracetamol per day.^{12<LE IV>} Current Australian dose recommendations of 15-20mg/kg per dose for those under 12 years of age, or under 40-50kg in weight, should limit doses to well below this level.^13,14

In addition, approximately one third of salicylate-sensitive children with asthma will have cross-reactivity to paracetamol.^{12<LE IV>} Reactions to paracetamol tend to occur later (i.e. 2-4 hours post-challenge) than those due to salicylates, and are less intense.^{15<LE III-1>}

Although both paracetamol and ibuprofen are widely used in Australia, there is a lack of published safety studies of their use in children with asthma. A recent study suggested that febrile asthmatic children treated with ibuprofen had a reduced risk of a subsequent outpatient visit for asthma compared to those treated with paracetamol. However, the study specifically excluded children with a known sensitivity to paracetamol, aspirin or any non-steroidal anti-inflammatory medication.  Thus, in a selected group of asthmatic children at low risk for ASA, the relative risk for an asthmatic episode was lower for ibuprofen, compared to paracetamol.^{16<LE II>} A prospective, randomised, double blind trial comparing paracetamol with ibuprofen in children with asthma is required before one of these two agents can be recommended over the other.

Naturally occurring salicylates are also present in many foods, and several studies have established that children with asthma can develop bronchospasm following oral salicylate ingestion. Prevalence rates for salicylate sensitivity in childhood asthma have varied from 13-28%, depending on dosage and the definition of what constitutes a significant response.^{17,18 <LE II>,  19,20 <LE IV>, 21<LE III-1>} Bronchospasm most often occurs within 30 minutes of ingestion, but can occur up to four hours after challenge.^{17<LE II>} Unfortunately, elimination of dietary salicylates does not appear to improve asthma control, although compliance with the restrictive diet was doubtful in the one study examining this.^{21<LE III-1>}