Antiviral Medications in Seasonal and Pandemic Influenza

Background: Amantadine, oseltamivir, and zanamivir are currently available in Germany for the prevention and treatment of influenza. We review their efficacy and side-effect profiles.

Methods: This review is based on pertinent randomized and controlled trials (RCTs) and systematic reviews retrieved by a systematic literature search, and on other relevant literature.

Results: The efficacy of antiviral drugs for the prevention of symptomatic influenza ranges from 60% to 90% (number needed to treat [NNT], 8-89) depending on the population and type of drug in question. Antiviral drugs shorten the duration of illness by 0.5-1.5 days when given within 48 hours of the onset of symptoms. Neuraminidase inhibitors do not significantly lower the incidence of bronchitis in adults, or of otitis media in children; they do have a positive effect against reported, but not necessarily diagnostically confirmed pneumonia in adults (NNT, 89 [50-232]). The RCTs yielded no information about possible effects on severe cases of influenza, or on mortality, as they included only mildly or moderately ill patients, but observational studies have yielded some evidence of benefit. The most common side effects of oseltamivir (>10%) are headache, nausea, and vomiting; of zanamivir (>1%), a skin rash; and of amantadine (>1%), loss of appetite, nausea, and central nervous effects.

Conclusion: The benefits of antiviral drugs, particularly neuraminidase inhibitors, outweigh their risks. In deciding whether to use them, physicians should consider the properties of the currently circulating viruses and the patient's individual risk constellation, as directed in clinical treatment recommendations.