Study casts doubt on paracetamol use for managing flu symptoms

Taking paracetamol to manage influenza makes no difference in terms of fighting the virus, reducing patients’ temperature or alleviating other symptoms, according to the results of what researchers claim is the first placebo-controlled trial to assess the impact of the over-the-counter drug on adults with confirmed flu.

“We initially theorised that taking paracetamol might be harmful, as the influenza virus cannot replicate as well at higher temperatures, and by reducing a person’s temperature the virus may have thrived,” says study author Irene Braithwaite, deputy director of the Medical Research Institute of New Zealand. “Fortunately this was found not to be the case.”

The researchers observed no difference between adults given paracetamol or placebo for symptoms scores, temperature, or the time it took for the virus to resolve. But the team caution against abandoning the common public health message for managing the common winter virus.

The paper, published in Respirology
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on 6 December 2015, says: “It is difficult to infer benefit or harm given the lack of effect of regular paracetamol administered early in the course of an influenza-like illness in this trial; thus, recommendations for or against this practice in the community cannot be made based on these findings. 

The researchers recruited 80 adults aged 18–65 years who had symptoms of influenza-like illness — a history of fever or recorded temperature of more than 37.8 degrees and at least one other symptom of a cough, sore throat, rhinorrhoea, headache, myalgia, fatigue or malaise for less than 48 hours.

The volunteers were screened for influenza A or B strains. Only those who tested positive were eligible for the randomised double-blind placebo-controlled trial. Of the 46 who tested positive, 22 were given 1g of paracetamol four times a day for five days; the other 24 received placebo.

Researchers took nasal swabs to test viral loads at day one, two and five. Temperature and symptom scores were also recorded for 5–14 days or until the viral infection had resolved.

“Regular daily administration of the maximum recommended dose of paracetamol for five days had no effect on viral shedding, temperature or clinical symptoms in participants with PCR-proven influenza infection,” the researchers conclude.

Richard Pebody, head of influenza surveillance at Public Health England, says that while the study is interesting more research is needed.

“Most influenza-like illnesses are self-limiting and the current guidance is to rest, drink plenty of fluids and take analgesics if required (paracetamol for all ages, aspirin may be taken by adults),” he says.

Medical advice should always be sought if symptoms become severe or last more than about a week, he adds, and people with “chronic or long-standing illness may need medical attention earlier”.

A National Institute for Health and Care Excellence (NICE) clinical knowledge summary for influenza — which reflects available evidence and was updated in October 2015 — recommends that patients take regular paracetamol and ibuprofen for the “symptomatic relief of influenza on the basis that they reduce fever and pain (including headache and myalgia)”.

John Smith, chief executive of the Proprietary Association of Great Britain, which represents over-the-counter medicines manufacturers, says: “While we note the findings, the researchers themselves acknowledge that it is difficult to make a recommendation for or against the use of paracetamol in adults with influenza based on these results.”

He adds that paracetamol is widely regarded as an all-round pain reliever and helps lower body temperature and is approved by the UK medicines regulator for relieving the symptoms of pain and flu.