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Inhaled drug useful in preventing flu An antiviral drug administered once daily during flu outbreaks may be useful in preventing flu type A and B, according to an article in a recent issue of The Journal of the American Medical Association (JAMA).  Arnold S. Monto, M.D., of the University of Michigan School of Public Health in Ann Arbor, and colleagues studied the use of the drug zanamivir as preventation for flu.  A total of 1,107 healthy adults from Ann Arbor, Mich., and Columbia, Mo., participated in a study in which half received a placebo and half  inhaled 10 mg. of zanamivir once a day for four weeks during local flu outbreaks.  The drug was found to be 67 percent effective in preventing laboratory-confirmed clinical influenza infection. It was found to be 84 percent effective in preventing laboratory-confirmed illnesses with fever.  Of the people studied, 14 percent had received a flu vaccination prior to participating in the trial. To date, there have been two antiviral drugs—amantadine and rimantadine—found to be effective in preventing the flu. However, the researchers say there have been concerns about those drugs.  “Concerns raised included the lack of effectiveness against type B viruses, occurrence of adverse effects mainly related to amantadine, and the rapid development of resistance to both agents,” the authors write. In this study, adverse effects thought by the investigators to be potentially drug-related were observed in 5 percent of the placebo group and 5 percent of the zanamivir group. Zanamivir has been demonstrated to be effective in clinical trials in shortening the duration and reducing the severity of type A and B flu. The authors write that use of drugs to prevent flu as an adjunct to vaccination has been considered useful in specific situations and this will continue to be the case.  “One of these situations was exhibited in 1997-1998, when a change in the circulating virus limited the efficacy of the vaccine. Another would be when a person in the risk groups recommended for vaccination is found to be unvaccinated by medical personnel after influenza transmission has started. In this case, vaccine could be administered and the drug given and continued for at least the limited period while antibody develops. “Also, outside the high-risk group, a decision may sometimes be made between a patient and medical personnel to use drug prophylaxis for a short period of exposure, such as when traveling, or for longer periods, when virus is known to be transmitting,” the authors write.  “These approaches have been used in the past with amantadine and rimantadine, and they should serve as guidelines for the use of zanamivir, recognizing its advantages over the older compounds.”