The use of antipyretic drugs (e.g. acetaminophen, better known as paracetamol) is recommended by various international guidelines (including the British Infection Society) for viral infections related to floods accompanied by fever, including influenza. Doctors and patients believe that using paracetamol with this viral infection can help and is unlikely to be harmful. In animal model studies, the use of antipyretics increases mortality from influenza. However, a new study, published in the December issue of the journal Respirology, found that using paracetamol 4 times a day with the flu has no benefits or drawbacks.

Theoretically, lowering the temperature of the flu, which is an adaptive response to infection, can actually worsen the course of the disease. Researchers at the Medical Research Institute (Wellington, New Zealand) have evaluated the effects of paracetamol on viral and clinical outcomes in adult patients with influenza.

In a randomized, double-blind, placebo-controlled study in which adult patients aged 18 to 65 years with flu symptoms and a rapid positive test to determine influenza antigens in smears from the nasal mucosa involved in 2011 and 2012, participants (n = 80) received either 1 g paracetamol 4 times a day or a placebo for 5 days. Smears of the nasal mucosa for the quantitative PCR diagnosis of the influenza virus were taken during the initial visit, then on the 1st, 2nd and 5th days of the disease. The temperature and assessment of symptoms of the disease were recorded for 5-14 days or until symptoms were completely relieved, respectively. The main parameter evaluated during the study was the area under the curve of the decimal logarithm (Log10) of the viral load using quantitative PCR from the initial visit on the 5th day of the disease.

In the paracetamol and placebo groups, 24 and 22 patients gave positive results for the determination of the influenza virus by PCR, respectively. The mean area under the Log10 viral load curve using quantitative PCR was 4.40 (0.91) in the placebo group and 4.64 (0.88) in the paracetamol group (the difference was - 0.24, 95% CI -0 78 - 0.29, p = 0.36).

All study participants showed no difference in the severity of flu symptoms in terms of a point score, temperature, time to resolution of illness, and overall health.

Thus, paracetamol does not affect the spread of the virus, fever and clinical symptoms in patients with influenza confirmed by PCR diagnostics. In this regard, the evidence base is currently insufficient for recommendations on the use of paracetamol for influenza.