Every year, starting around November or December, millions of us succumb to the muscle aches, fever, cough, and chills associated with the flu. While an effective flu vaccine is available, usually only the elderly or people with weakened immune systems line up to receive it, while many other people who could benefit do not. For the unlucky of us who contract the flu this fall, several medications may help.
In 1918, the influenza virus infected and killed more than 20 million people worldwide. It was the worst flu epidemic ever recorded. Despite two further pandemics since this catastrophe, influenza has been relatively milder in recent years.
However the flu virus is still a serious public health problem. Estimates vary, but approximately 25-30 million Americans get the flu each year. Although most of us struggle through it and feel better in about a week, as many as 20,000-40,000 people die from it in the US each year. They are usually the elderly, infants, and people with chronic illness. Experts worry that a new worldwide pandemic, possibly caused by avian or
“bird” influenza
, might be even more widespread and deadly than the 1918 outbreak.
There are three types of influenza virus that affect humans: A, B, and C. The first two, A and B, cause the most serious illness. Amantadine and rimantadine have long been available to control symptoms of influenza caused by the A type of virus. These closely related drugs, when given within the first 48-72 hours of becoming sick (or in some circumstances even before exposure to the illness), can significantly reduce the severity and duration of influenza.
However amantadine and rimantadine work only for influenza A. There is no consistent difference in symptoms between the two influenza types, and testing may not always be available to help decide whether or not these drugs will work. Both drugs can affect the central nervous system and cause undesirable side effects. These are more common with amantadine. Drug resistance to these medications is also common, meaning that they may not work for some flu-infected people, particularly those in nursing homes or hospital settings.
Relenza (zanamivir) was the first drug approved for treatment of both influenza A and B. Relenza was the first new flu drug the FDA had approved since Flumadine (rimantadine) in 1993. The US Food and Drug Administration (FDA) approved Relenza for the treatment of acute influenza virus A and B in adults and children seven years or older who have been symptomatic for no more than two days.
The clinical data on Relenza reveals a mixed bag. In a US trial of 780 people, treatment with the drug, when initiated within 48 hours of onset of symptoms, reduced the normal seven-day flu course by only one day. But studies conducted outside the US have suggested that Relenza could reduce flu symptoms by as much as 2-2.5 days. People with more severe symptoms are more likely to notice improvement.
A study found that Relenza prevented the spread of the flu virus between family members in 79% of study participants. Among 337 families studied, only 4% had one or more family members contract the flu after treatment, compared with 19% of those taking a placebo. The study's lead scientist, Frederick Hayden, MD, said that although the annual flu vaccine is the best way to prevent the disease, "with Relenza we have an additional way to prevent the disruption that influenza can cause in families."
Relenza is an inhaled treatment that is administered by a breath-activated device called the Diskhaler, which delivers the drug directly into the lungs, the site of an influenza infection. When used twice a day for five days, Relenza prevents the natural cycle of the flu by interfering with an enzyme called neuraminidase. The medication blocks the ability of the flu virus to attack your cells.
Adverse side effects don't seem to be a big issue with Relenza. In clinical studies, only about 3% of patients experienced
sinusitis
,
diarrhea
, or nausea—the three most common side effects identified so far.
Asthma
patients are the exception; some patients with mild or moderate asthma suffer an acute shutting down of the airway (called bronchospasm) after inhaling Relenza. Because of the risk of bronchospasm, the FDA specifically states that Relenza may carry a risk in patients with severe or decompensated asthma or
chronic obstructive pulmonary disease (COPD)
—a serious lung disorder.
On January 12, 2000, the FDA issued a public health advisory alerting healthcare professionals that it had received several reports of deterioration of respiratory function following inhalation of Relenza in patients with underlying asthma or chronic obstructive pulmonary disease (COPD). As a result, the FDA recommended that "in such patients, Relenza should be used under conditions of careful monitoring, proper observation and appropriate supportive care, including the availability of short-acting bronchodilators."
Unfortunately, even some people who do not have known asthma will also develop bronchospasm after using Relenza. This side effect may be severe enough to require medical treatment.
Tamiflu (oseltamivir) is from the same family of drugs as Relenza and acts in a similar way. But it is administered in pill form, rather than inhalant, and as a result, is free from the respiratory side effects that plague Relenza.
In one of two studies published in the
Journal of the American Medical Association
in 1999, Tamiflu reduced symptoms and duration of the flu by about half in 56 unvaccinated adults voluntarily infected with the virus. However, across all studies, the drug can only shorten flu by an average of 1-1½ days. There is less evidence that this or any of the antiviral drugs prevent serious flu complications. However, scientists are hoping that oseltamavir may prove to be a crucial tool for limiting the spread of avian influenza if it becomes more widespread among human populations.
Tamiflu may also help prevent the flu. Tamiflu has been FDA-approved for influenza A and B prevention in people age 13 or older. In the second Tamiflu study, only 38% (8 of 21) of those taking the drug were infected when exposed to the virus, compared with 67% (8 of 12) who didn't receive the medicine. The FDA approved Tamiflu for prevention in November 2000, though cost considerations (a single dose typically costs $7 or more) may strongly limit its daily use for prevention.
The best way to avoid the flu altogether is to get vaccinated. Dr. Hayden, who has studied Relenza and Tamiflu extensively, believes that these new drugs aren't a substitute for the flu vaccine. The annual flu shot is composed of three inactivated viruses that change each year depending on the predominant strains in circulation. Current reports suggest that there won’t be any flu vaccine shortages during the 2007-2008 flu season, so you should be able to get a vaccine at your doctor's office, nearby health center, or pharmacy.
The Centers for Disease Control and Prevention (CDC) strongly recommends a flu shot for all people age 50 years or older, infants 6-23 months of age, and people of any age with chronic diseases of the heart, lung, or kidneys,
diabetes
, immunosuppression, or severe forms of
anemia
. The CDC also suggests that residents of nursing homes and other chronic-care facilities receive the vaccine. Given sufficient vaccine availability, all persons should consider vaccine to reduce their risk of getting sick.
The US flu season occurs between November and April, with peak activity from late December through early March. The best time to receive a flu shot is sometime in October or November. It takes about one to two weeks after vaccination to develop protection against the flu virus.
