TAMIFLU® (oseltamivir phosphate) has been studied only in strains of influenza that were circulating at the time. The magnitude of effect of TAMIFLU in treating and preventing novel strains of influenza, such as those that may be involved in a pandemic, cannot be predicted.
Why are the health experts concerned about avian flu?
H5N1
The current strain of bird flu infecting poultry flocks in Asia-H5N1-is highly
contagious among birds and has resulted in the death or destruction of over 150
million birds. The outbreaks are the most widespread and severe on record.
Infected birds often die within two days. As of early 2006 birds in at
least 30 countries have been affected.
Because such viruses rarely infect people, however, scientists fear we may have
little or no immunity to them, making us particularly susceptible to illness should
H5N1 undergo the mutations necessary to spread among humans.5
High mortality rate in humans
Since 2003, there have been nearly 200 documented cases of human infection with
H5N15 among people working in close contact with infected domesticated birds in
Asia, Europe and other parts of the world.3,5
According to the World Health Organization, in the first 194 cases of bird-to-human
transmission of H5N1, there were 109 deaths.6 In other words, more than half of
those infected have died. This mortality rate of roughly 56% is one reason public
health authorities worldwide are so concerned.
Person-to-person spread unconfirmed5
Thus far, it seems difficult for humans to acquire the virus from birds and even
more difficult for the virus to spread among people. In fact, no suspected cases of
person-to-person transmission have been confirmed thus far. This indicates that the
species barrier is still fairly strong.
However, given how devastating H5N1 has been both for birds and the small number
of humans it has infected, health experts are concerned that further mutations of
H5N1 could change the virus into a form easily transmitted from person-to-person,
resulting in a worldwide outbreak of the disease, or "pandemic."
FOOTNOTE
3. Avian vs. pandemic flu: understanding the threat [press release]. Pan American
Health Organization. Available at: http://www.paho.org/english/dd/pin/pr051220.htm. Accessed April 19, 2006.
5. Stimola AN. Avian Influenza, or "Bird Flu": What You Need to Know. New York, NY:
American Council of Science and Health; 2006.
6. World Health Organization. Cumulative number of confirmed human cases of avian
influenza A/(H5N1) reported to WHO. April 12, 2006.
Available at: http://www.who.int/csr/disease/avian_influenza/country/cases_table_2006_04_12/-
en/index.html.Accessed Apirl 13, 2006
Indications
TAMIFLU is indicated for the treatment of uncomplicated influenza caused by viruses types A and B in patients 1 year and older who have been symptomatic for no more than 2 days.
TAMIFLU is also indicated for the prophylaxis of influenza in patients 1 year and older.
TAMIFLU is not a substitute for early and annual vaccination as recommended by the Centers for Disease Control's Advisory Committee on Immunization Practices (ACIP).
Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.
Safety Information
There is no evidence for efficacy against any illness caused by agents other than influenza types A and B.
Treatment efficacy in subjects with chronic cardiac and/or respiratory disease has not been established. No difference in the incidence of complications was observed between the treatment and placebo groups in this population.
No information is available regarding treatment of influenza in patients at imminent risk of requiring hospitalization.
Efficacy of TAMIFLU has not been established in immunocompromised patients.
Safety and efficacy of repeated treatment or prophylaxis courses have not been studied.
Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease. There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving TAMIFLU. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on TAMIFLU usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of TAMIFLU to these events has not been established. Patients with influenza should be closely monitored for signs of abnormal behavior. If neuropsychiatric symptoms occur, the risks and benefits of continuing treatment should be evaluated for each patient.
In postmarketing experience, rare cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome and erythema multiforme, have been reported with TAMIFLU.
The most common adverse events reported >1% of patients treated with TAMIFLU and more commonly than in patients treated with placebo are:
Treatment of adult and pediatric patients - nausea, vomiting.
Prophylaxis of adult and pediatric patients - nausea, vomiting, abdominal pain.
Vaccination is considered the first line of defense against influenza.
