NEW YORK, Oct 05 (Reuters Health) -- An oral drug appears to be effective for both the prevention and early treatment of one type of influenza, according to study results published in the October 6th issue of The Journal of the American Medical Association.
The drug oseltamivir, given by mouth to healthy volunteers who had been inoculated with the influenza A virus, prevented influenza A infection in a significant number of participants. In other healthy subjects who became sick after influenza A inoculation, oseltamivir lessened the duration and severity of flu symptoms.
Oseltamivir has yet to be approved by the Food and Drug Administration (FDA), but lead researcher Dr. Frederick G. Hayden of the University of Virginia Health Sciences Center in Charlottesville predicts that the FDA will act on the drug by the end of October.
"I think the treatment data are convincing that oseltamivir is both safe and effective when used for treatment" of flu, Hayden said in a telephone interview with Reuters Health. "With early treatment, we see about a day and a half reduction in illness duration, about a 30% reduction in symptom severity, a more rapid return to usual activity and nearly a halving of the risk of complications leading to antibiotic use, compared with placebo," he said.
Hayden's team conducted two studies of the drug in the summer of 1997 -- one designed to see if oseltamivir could prevent influenza infection and the other designed to see if the drug could be an effective treatment for influenza infection. A total of 37 healthy adult volunteers participated in the prevention trial and 80 participated in a treatment trial.
In the prevention trial, participants received placebo (dummy pills) or oseltamivir, 100-milligram tablets once daily or twice daily, starting 26 hours prior to inoculation with the flu virus and continuing for 5 days after inoculation. According to Hayden and colleagues, 67% of placebo-treated subjects became infected with influenza compared with only 38% of oseltamivir-treated subjects. None of oseltamivir-treated subjects developed a respiratory illness related to influenza infection compared with roughly a third of placebo-treated subjects.
In the treatment trial, subjects received either placebo or 20, 100 or 200 milligrams oseltamivir twice daily or 200 milligrams oseltamivir once daily starting 28 hours after influenza inoculation and continuing for 5 days after inoculation. Oseltamivir-treated subjects experienced milder influenza-related symptoms for a shorter period of time than placebo-treated subjects did. No significant dose-related differences emerged and oseltamivir was well tolerated.
Hayden also told Reuters Health that a 'field trial' conducted among a nursing home population during the last influenza season support the data in the study, which are based on experimentally induced flu in healthy volunteers. In that field trial, "oral oseltamivir given once daily for a 6-week period was well tolerated and was associated with a 92% protection against influenza illness in nursing home recipients compared with placebo," Hayden said.
While flu vaccination "remains the mainstay of prevention," Hayden believes there are a number of situations in which oseltamivir could be useful for prevention such as for "late-season immunization, postexposure prophylaxis in families, outbreak control," as well as in people who do not respond to influenza vaccination.
