"Experiences clearly show that to reduce mortality patients should receive treatment with oseltamivir as early as possible, but treatment remains effective even when patients present late," commented Professor John Oxford, Professor of Virology at St Bartholomew's and the Royal London Hospital, "H5N1 has proven to be an extremely virulent virus in humans and in some countries we have seen the need to use higher and longer doses of oseltamivir to gain maximum benefit."
The latest advice is based on evidence presented to the WHO by experts in countries that have reported human cases of bird flu. Tamiflu is the only neuraminidase inhibitor to have been used in the management of human cases of H5N1 and is the only antiviral strongly recommended for treatment of H5N1 infected patients by the WHO.
With this latest evidence WHO recommends:
Standardising care and promptly sharing clinical and treatment information to improve understanding of the disease and identify appropriate therapy.
Tamiflu remaining the primary antiviral treatment both early and late in the infection as there is evidence of prolonged replication with H5N1.
Modified Tamiflu treatment regimens - higher and longer dosing may be necessary given the virulence of some forms of H5N1 seen recently.
Possible combination therapy with adamantanes (case by case basis), particularly in patients with pneumonia or progressive disease.
The guidance also states that inhaled zanamivir has not been studied in human H5N1 illness and that the adequacy of inhaled zanamivir delivery in patients with serious lower respiratory tract or extra pulmonary disease is a major concern. Ongoing modifications will be made to the WHO guidance based on continual research findings.
During the clinical development programme Roche carried out studies looking at higher doses of Tamiflu. The safety profile at these higher doses was supportive of further investigation A high versus standard dosage study has recently started in patients with severe influenza, both H5N1 and seasonal, in conjunction with the National Institutes of Health (NIH), to determine which is the most effective dose in severe disease.
WHO coordinates the global response to human cases of H5N1 avian influenza and tracks the corresponding threat of an influenza pandemic, providing access to both technical guidelines and information useful for the general public.
Tamiflu is an oral neuraminidase inhibitor that is active against all strains of influenza A and B tested. More than 80 governments worldwide are now stockpiling Tamiflu in preparation for a pandemic and many global businesses are in discussions with Roche and are now stockpiling for their employees and their families in line with local laws and regulations.