FDA: Safety Warning Issued for Influenza Drug Relenza

April 3, 2008

The maker of the antiviral drug Relenza (zanamivir) informed health care professionals this week of a potential risk of behavioral changes and delirium associated with the drug's use. Relenza is approved for the treatment of influenza A and B.

THURSDAY, April 3 (HealthDay News) -- The maker of the antiviral drug Relenza (zanamivir) informed health care professionals this week of a potential risk of behavioral changes and delirium associated with the drug's use. Relenza is approved for the treatment of influenza A and B.

GlaxoSmithKline, the manufacturer of Relenza, shared information from postmarketing reports of delirium and abnormal behavior leading to injury in patients with influenza taking neuraminidase inhibitors, including Relenza. These events occurred primarily in children, and were often associated with abrupt onset and rapid resolution. Based on usage data for Relenza, it appears that such neuropsychiatric events are uncommon. In addition, causation of these events by Relenza has not been definitively established.

Health care professionals are urged to monitor their patients taking Relenza for any signs of abnormal behavior, and consider discontinuing the drug should neuropsychiatric symptoms occur. In addition, any adverse events suspected to be related to Relenza use should be reported to the U.S. Food and Drug Administration.

The labeling of Relenza has been updated to reflect these new safety warnings. "GlaxoSmithKline will continue to monitor the safety of Relenza through established reporting mechanisms and notify regulatory authorities of any serious adverse events for evaluation," said Dr. Judith Ng-Cashin, M.D., GlaxoSmithKline's director, in a letter to health care professionals.

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