Giving double doses of the antiviral drug oseltamivir, or Tamiflu, offers no clinical or virological advantages over a standard dose for patients admitted to hospital with severe influenza infection, according to a randomised trial published and funded by the Wellcome Trust, US National Institute of Allergy and Infectious Diseases and the Singapore National Medical Research Council.

This is the first study to look at the effectiveness of higher doses of oseltamivir in cases of severe flu infection and has implications for global guidelines on clinical management and stockpiling drugs for pandemic preparedness, including the current outbreak of the H7N9 virus.

Most people who are infected with flu will recover in a few days or up to two weeks, but some people will develop complications, such as difficulty with breathing, that results in hospital admission and can be life-threatening.

Studies have shown that early treatment with oseltamivir is beneficial for patients with uncomplicated flu infection and improves survival in hospitalised patients with severe infection. This has led some authorities to recommend double doses of oseltamivir for treatment of patients with severe flu infections.

The study, conducted by researchers from the South East Asia Infectious Diseases Clinical Research Network, involved 326 patients with severe flu infection at thirteen hospitals in Indonesia, Singapore, Thailand and Vietnam. Most of the patients were children under the age of fifteen.

Patients were given either a standard dose or double dose of oseltamivir for five days. Their virus levels were monitored for the duration of the treatment along with other outcomes, such as admission to intensive care, the need for mechanical ventilation to assist with breathing and death.

The findings, published online today in the British Medical Journal, reveal no difference in virus levels at day five between either of the treatment groups. There were also no clinical differences in the outcome of patients including need for ventilation, time in hospital, rate of death, or rates of adverse events between the different doses.

Professor Jeremy Farrar, Director of the South East Asia Infectious Disease Clinical Research Network said: "The recommendation to give higher doses of oseltamivir to severe cases of flu infection has major implications for clinical management, public health, and planning for antiviral stockpiles but has not been grounded in evidence. Our findings do not support routine use of double doses to treat severe flu infections, which could help to conserve drug stocks in the event of a pandemic."