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Antiviral effective against flu but ‘may not outweigh harms’, study shows

Antiviral drug oseltamivir (Tamiflu) reduces flu complications and hospitalisations as well as symptoms, but these benefits may not outweigh its side effects, a new major study has concluded.

The meta-analysis, published today in the Lancet, found oseltamivir shortened flu symptoms by about one day, as well as cutting the need for antibiotics for lower respiratory tract infections by over 40% and reducing the risk of admission to hospital by about 50%.

However, it also showed oseltamivir increased the risk of nausea by nearly 4% and vomiting by 5%.

The authors argued the reductions in complications and hospitalisations – findings that were refuted by a recent Cochrane review – were robust findings, because their analysis included individual patient data from both published and unpublished trials, made available by the drug’s manufacturer Roche.

They did, however, question whether the impact of oseltamivir on these outcomes would outweigh the potential harms from gastrointestinal side effects.

Lead author Professor Arnold Monto, professor of epidemiology at the University of Michigan, said: ‘Our meta-analysis provides compelling evidence that oseltamivir therapy reduces by one day the typical length of illness in adults infected with influenza and also prevents complications and reduces the number of people needing hospital treatment.

‘Whether the magnitude of these benefits outweigh the harms of nausea and vomiting needs careful consideration.’

Today’s study comes after authors of the Cochrane review recently wrote to NICE questioning their continued support for use of antivirals.

Their meta-analysis – published last year – had found no evidence that oseltamivir reduced objectively measured pneumonia or hospitalisations from flu, sparking controversy over the Government policy to stockpile the drugs.

The recent Cochrane review also raised concerns that the drug caused neuropsychiatric side effects, but these were not seen in the Lancet study.

Professor Tom Jefferson, co-author of the Cochrane review and a former GP, said their conclusions likely differed – at least in part – because the Cochrane reviewers had been more stringent about the definitions of complications used in the trials, having scrutinised clinical study reports as well as the trials data.

Professor Jefferson said: ‘Had they looked at the protocols and blank CRFs they would have seen there is no “pneumonia” definition, no chest x-ray confirmation and in most clinical study reports secondary illnesses are mentioned only in the context of harms.’

Professor Jefferson also pointed out that the current study was indirectly funded by Roche, which funded the Multiparty Group for Advice on Science that paid for the analysis.