Oseltamivir: new preparation. An antiviral agent with little impact on influenza.

(1) Oseltamivir, an oral antiviral agent, has been marketed in the European Union for the prevention and treatment of suspected influenza during epidemics. (2) Three prevention trials done in the general population showed moderate effects, with a 3.5-4% reduction (in absolute values) in serologically confirmed episodes of 'flu. According to one trial, oseltamivir was moderately effective as a prophylactic for close contacts of 'flu cases (6.6% in absolute values). (3) There are three placebo-controlled double-blind trials evaluating oseltamivir as a treatment for 'flu, two in adults and one in children. (4) At a dose of 75 mg twice a day, oseltamivir shortened symptoms by about 24 hours. There was no evidence that oseltamivir prevented complications that need antibiotic therapy. Influenza virus isolates from adult patients belonged to type A in more than 90% of cases. There is no sound evidence that oseltamivir is effective against type B influenza virus. (5) There was no reduction in the frequency of complications in a trial in at-risk adults with chronic respiratory or cardiovascular disorders, or in a trial in asthmatic children. (6) Patients receiving oseltamivir in clinical trials were more likely to suffer nausea and vomiting than patients given placebo. (7) Oseltamivir has not been compared with oral amantadine or inhaled zanamivir. (8) It is best to use amantadine when prophylaxis is needed during epidemics. In the curative setting, the poor risk-benefit ratio of oseltamivir, zanamivir, and amantadine, argues against the use of these drugs.