The Food and Drug Administration (FDA) today approved the use of Relenza (zanamivir for inhalation) for prevention (prophylaxis) of influenza (flu) in adults and children 5 years of age and older. Relenza, an antiviral medication, was previously approved for the treatment of influenza A and B virus infections in adults and children. Tamiflu (oseltamivir phosphate) previously was approved for both prevention and treatment of flu; today's approval of Relenza for prevention provides Americans with another option for the prevention of influenza A and B infections.
"This approval is a welcome addition to the available defenses against the flu," said Dr. Steven Galson, director of the FDA's Center for Drug Evaluation and Research. "This new use offers the medical community another option to prevent and control influenza A and B."
The effectiveness of Relenza in preventing seasonal influenza has been demonstrated in four large-scale studies comparing the drug with placebo. In two of these trials, the use of the drug substantially reduced the spread of influenza in the participating households where participants were five years of age or greater. In both of these trials, the proportion of households that developed symptoms confirmed to be flu was 19 percent for the placebo group and 4.1 percent for the Relenza group.
In the other two trials, which were conducted in communities experiencing an influenza outbreak, Relenza reduced the incidence of the disease in both young and older populations. In the first study, with participants 18 years of age or older, the proportion of people who developed symptoms confirmed to be flu was 6.1 percent for the placebo group and 2 percent for the Relenza group. The second community study enrolled people 12 to 94 years of age (56 percent of whom were older than 65 years). In this trial, the percent of people who developed symptoms confirmed to be flu were reduced from 1.4 percent of the participants on placebo to 0.2 percent for those who used Relenza.
In all of these studies, the most common events during treatment with Relenza in adults and adolescents were headaches; diarrhea; nausea; vomiting; nasal irritation; bronchitis; cough; sinus infections; ear, nose, and throat infections; and dizziness. In children, the most common side effects were ear, nose, and throat infections; vomiting; and diarrhea. Less common reported events included rashes and allergic reactions, some of which were severe.
Breathing problems (bronchospasm), including deaths, were reported in some patients after the initial approval of Relenza. Most of these patients had asthma or chronic obstructive pulmonary disease. Relenza therefore is not recommended for treatment or prophylaxis of seasonal influenza in individuals with underlying airways disease such as asthma or chronic obstructive pulmonary disease.
Relenza has not been proven effective for treatment of influenza in people with underlying airways disease, or for prevention of influenza in nursing homes. The drug is also not a substitute for the flu vaccine, which is the primary means for preventing influenza. Consumers should continue receiving an annual flu vaccination according to guidelines on immunization practices.
In preparation for a potential pandemic, FDA has assembled an agency-wide Pandemic Influenza Preparedness Task Force to provide policy leadership and strategic planning on pandemic influenza. The Task Force is charged with developing a comprehensive plan to accelerate the development, production, and regulatory review of antivirals and other pandemic countermeasures.
The FDA also is working with the pharmaceutical industry to make available appropriate products and ensure that mechanisms are in place to collect the necessary efficacy and safety information. Both Relenza and Tamiflu have been identified for stockpiling.
Relenza is manufactured and distributed by GlaxoSmithKline Inc., based in Research Triangle Park, N.C.