University of Virginia Health System

ORAL MEDICATION EFFECTIVE IN LONG-TERM PREVENTION OF NATURALLY OCCURING FLU

Dr. Frederick C. Hayden, professor of internal medicine at the University of Virginia Health System, and colleagues, studied the use of oseltamivir over a six-week period in two randomized, placebo-controlled, double-blind trials during flu outbreaks in the winter of 1997-98.

Although a yearly flu shot is still the best way to prevent influenza, this drug provides a supplemental means of protection, Hayden said. For example, in the case of the rapid spread of a new flu virus, this type of antiviral drug could play a major role in protecting people while the specific vaccine was being developed. Or if someone waited to get the vaccine until flu activity had already started, oseltamivir could be used to provide immediate protection while waiting for a response to the vaccine.

The study, which involved 1559 healthy adults who ranged in age from 18 to 65, was conducted at centers in Virginia, Texas and Kansas. Eight to 12 weeks before the anticipated start of the peak flu season, people were enrolled in the study. When there was a local increase in influenza virus activity, participants returned to the study center to begin drug administration.

The study participants were given 75 mg of oseltamivir orally once or twice daily, or a dummy pill for six weeks. Participants used daily diary cards to record their oral temperature, any medications taken, times of drug administration and the presence or absence of seven key flu symptoms: chills or sweats, aches, fatigue, headache, cough, sore throat and nasal congestion.

Return visits were scheduled for week three, week six (within three days after the final dose of the study medication had been taken) and week eight (or 10 to 14 days after the final dose). People in the trial also were instructed to return to the clinic if fever or other symptoms of influenza developed; at these visits, nasal and pharyngeal swabs were collected for influenza virus culture.

Although the rates of influenza in the study populations were low and variable, overall there were was a 74 percent protection rate in laboratory-confirmed flu and an 87 percent protection rate in culture-positive influenza. At the three Virginia centers, once daily oseltamavir was 84 percent protective against influenza illness.

The study findings demonstrate that oral oseltamivir is effective in preventing naturally occurring influenza and that it is well tolerated during long-term administration, Hayden said. The most common side effect was minor gastrointestinal disturbances or nausea that usually dissipated after the first week.

These findings confirm the results of earlier studies of experimental influenza in humans in which 100 mg of oral oseltamivir taken once daily was highly protective against infection-associated illness.

Oseltamivir, which is produced by Hoffman-LaRoche, currently is being reviewed by the U.S. Food and Drug Administration (FDA).

October 27, 1999