By Leah Shafer

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s we enter the flu season again, it's a good time to take stock of two antiviral drugs that were released in 1999 to fight the influenza virus, better known as the flu. Nearly 1 million Americans rushed to the doctor last winter for zanamivir (Relenza) and oseltamivir phosphate (Tamiflu), new antiviral drugs approved by the Food and Drug Administration (FDA) in 1999. In clinical studies, if started within two days after symptoms appear, these medications were shown to be moderately effective in increasing the rate of recovery.

This winter, doctors should expect even more patients to request the two antiviral therapies, because in addition to treating the flu, Tamiflu has been approved by the FDA to prevent people from getting the nasty bug in the first place. Relenza is under review by FDA for the same thing.

Given the serious delays and shortages of flu vaccine in 2000, and health officials' recommendation that healthy people delay getting their shot until high-risk groups are vaccinated, Tamiflu and Relenza may get their chance to be all-stars in this season's prevention efforts.

An ounce of prevention

In recent studies, both Relenza and Tamiflu showed dramatic results in preventing the spread of the flu virus. Tamiflu, a pill marketed by Hoffmann-LaRoche, reduced the risk of catching the flu by up to 92 percent. In a study by the University of Virginia Medical Center, Glaxo Wellcome's inhalant Relenza was 79 percent effective.

Tamiflu and Relenza are not meant to replace the flu vaccine, but when an immediate member of the family gets ill, or for certain high-risk groups, these medications might be well worth the money.

But when you look at the difference in cost between the flu shot and these medications, they lose some of their appeal. A 10-day supply of Tamiflu costs $49 wholesale; five days of Relenza is $48. An entire season of either could run into the hundreds of dollars.

In contrast, flu shots are often covered through insurance or Medicare or are available low-cost at public health clinics.

These antiviral medications are not meant to replace the flu vaccine, but when an immediate member of the family gets ill -- or for certain high-risk groups, such as the elderly or immune-compromised -- these medications might be well worth the money.

The flu shot: good as gold

The number of people who took advantage of these new medications falls far short of the 75 million Americans who tried to prevent infection by getting the flu shot instead. With a 70 to 90 percent effectiveness rating, the influenza vaccination remains the primary means to prevent and control the spread of the virus and, as such, is the true MVP of the flu season.

Officials at the Centers for Disease Control and Prevention (CDC) agree that the flu vaccination is the preferred choice. In a December 1999 report, the agency's doctors commented that "antiviral agents are an adjunct ... not a substitute for the vaccine."

The vaccine allows people to be proactive about their health and not wait for the misery of flu to knock them flat.

"From a public health perspective, the ideal would be for at-risk folks to get vaccinated [for the flu] and not wait until they get it," says Heidi Jolson, M.D., director of the Division of Antiviral Products at the FDA.

Bacteria or virus? A tough call

Many medical experts would like patients to keep the flu shot as their primary defense not only because it is cheaper and very effective, but because it's easy for doctors to confuse viral and bacterial infections. Since both Relenza and Tamiflu must be started within two days of symptom onset, many people who felt the flu coming on rushed to the emergency room or to their physician to get the new medications. Unfortunately, with the pressing need to make an early diagnosis, several patients who didn't, in fact, have the flu were given these antiviral medications, only to see their symptoms remain unchanged or worsen.

In mid-January 2000, the FDA issued a public advisory in a memo to health care professionals cautioning them against being too heavy-handed in prescribing the new flu drugs. In it, Murray Lumpkin, M.D., the deputy director of the Center for Drug Evaluation at the FDA, noted several cases in which patients with influenza-like symptoms actually had severe bacterial infections that worsened during antiviral therapy.

Dr. Lumpkin also advised physicians to be cautious in prescribing Relenza for patients with underlying asthma or chronic obstructive pulmonary disease. Relenza is known to cause respiratory problems in some of those patients.

At the time Relenza and Tamiflu were introduced last fall, there was tremendous media attention given to the coming flu season and to the prospect of drugs that could fight off its worst effects, Dr. Jolson said. Last winter, Glaxo Wellcome, maker of Relenza, and Hoffman-LaRoche, maker of Tamiflu, targeted cities hardest hit with influenza with heavy advertising ranging from full-page newspaper ads to television commercials. The resulting public clamor for these flu drugs prompted the FDA advisory last January.

"We thought we'd remind doctors and patients that symptoms of bacterial infections can be similar to those of the flu, and that patients with the flu may also have a bacterial infection," Dr. Jolson said.

Relenza and Tamiflu will surely step up to the plate many times during the next flu season, both for prevention and cure, but the flu vaccination remains the heavy hitter against the virus.

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