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Pandemic Planning Toolkit A resource to assist your organization in preparing for pandemic influenza

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.

What evidence supports TAMIFLU activity against avian flu?
Non-human data do not necessarily indicate clinical activity in humans. To date, results from clinical studies in humans are not available. Data from in vitro and animal studies that have been performed are summarized below

Tamiflu 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 or associated with avian flu) cannot be predicted.

Tamiflu has not been proven to have a positive impact on the potential consequences (such as hospitalizations, mortality, or economic impact) of seasonal, avian, or pandemic influenza
.

In vitro activity (i.e. outside an organism) against H5N1

  • One study compared viral activity of 4 novel neuraminidase inhibitors, zanamivir and oseltamivir , against various strains of influenza A and B viruses (including 2 strains of H5N1 avian virus). The analysis demonstrated a high level of viral inhibitory activity by all compounds against the specified H5N1 strains (A/duck/MN/1525/81 and A/gull/PA/4175/83) of avian influenza.41a

In vivo activity (in mice) against H5N1 and H9N242

  • One study in ferrets showed that TAMIFLU administered 4 hours after inoculation prevented viral replication in the upper respiratory tract and effectively treated all infected ferrets with no deaths. All ferrets in the control group died.41b
  • Another in vivo study in mice tested oseltamivir for protection against avian strains H5N1 and H9N2. The results showed that oseltamivir provided complete protection against the H5N1 virus starting at a dose of 0.1 mg/kg/day and against the H9N2 virus starting at a dose of 1.0 mg/kg/day. Additionally, oseltamivir was tested as a treatment regimen for the H5N1 virus. The treatment was incrementally delayed from 24 to 60 hours, and oseltamivir was shown to significantly increase the survival rates of mice (65%-90%) as compared with the untreated group (0% survival).

Learn more about the role of the government with respect to supply of TAMIFLU.

 
FOOTNOTE
41a. Smee DF, Huffman JH, Morrison AC, Barnard DL, Sidwell RW. Cyclopentane neuraminidase inhibitors with potent in vitro anti-influenza virus activities. Antimicrob Agents Chemother. 2001;45:743-748.
41b. Govorkova E.A and Webster R.G., Evaluation of oseltamivir in lethal H5N1 in vivo model. Presented: 20 January, 2006 at The First Pandemic of the 21st century - a central role for antivirals conference, London.
42. Govorkova EA, Leneva IA , Goloubeva OG, Bush K, Webster RG. Comparison of efficacies of RWJ-270201, zanamivir, and oseltamivir against H591, H9N2, and other avian influenza viruses. Antimicrob Agents Chemother . 2001;45:2723-2732
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.

Please see TAMIFLU full Prescribing Information for additional safety information.
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