Zanamivir (Relenza) should be used with "special caution" in patients with asthma or chronic obstructive pulmonary disease (COPD), according to an advisory letter sent to all physicians by the manufacturer, Glaxo Wellcome.
The letter, which was sent at the request of regulatory bodies, follows "a handful" of adverse events, including bronchospasm and/or decline in respiratory function associated with the use of zanamivir. The company says that the events have been reported "rarely" in patients with asthma or COPD and "very rarely" in patients with no underlying respiratory disease. Glaxo Wellcome adds that, while these adverse events might be due to the use of Relenza, the precise determination of the cause is difficult given the nature of influenza, the presence of underlying disease and the use of concomitant medication in many of the cases reported.
It recommends that "patients with asthma or COPD should be informed of the potential risk of bronchospasm when using Relenza and advised to ensure that a fast-acting bronchodilator is available. Patients on maintenance bronchodilator therapy should be advised to use their bronchodilator before taking Relenza". A spokesman from Glaxo Wellcome told The Journal on January 26 that pharmacists will shortly receive a letter notifying them of the reports, together with an updated SPC.
Zanamivir was launched last September (PJ 1999;263:374) and, since the start of the influenza season in October, 500,000 prescriptions have been written worldwide of which 8,000 were from the UK.
The National Institute for Clinical Excellence (NICE) recommended that the drug should not be made available for prescription on the NHS (PJ 1999;263:561). A further review by the NICE is to be published in September.