The manufacturer of zanamivir (Relenza® Glaxo-Wellcome Inc.), has circulated an important warning on revisions to the safety labelling of the product, which was approved in 1999 for the treatment of uncomplicated acute illness due to influenza virus.

The warning describes reports of bronchospasm and decline in lung function in some patients and states that zanamivir is not recommended in patients having underlying airways disease, such as asthma or chronic obstruction pulmonary disease. Fatal events have been reported and information has been added on allergic-like reactions including the potential for masking of serious bacterial infections which may present as influenza-like symptoms. New animal toxicity data have also led to a change in the information on use in pregnancy.

Reference: Letter from Glaxo Wellcome, July 2000 available from US Food and Drug Administration on http://www.fda.gov/medwatch/safety/2000/relenz.htm