Use of antivirals to treat H1N1 flu virus

May 1, 2009 - 18:14 EST

As experts around the world continue to learn more about the H1N1 flu virus (human swine flu), questions are arising about the best way to treat and prevent the spread of this illness.

Antivirals are drugs that can treat the symptoms of an influenza virus infection and reduce the spread of the illness to others, but only if they are administered early. These drugs have to be administered within 48 hours of the beginning of symptoms in order to be optimally effective.

Early research shows us that the H1N1 flu virus can be treated effectively with two different types of prescription antiviral drugs, one called oseltamivir (Tamiflu), and another called zanamivir (Relenza). H1N1 flu virus (human swine flu) is a different virus than some other recent seasonal human influenza H1N1 strains which were resistant to oseltamivir.

So far, the illnesses reported in Canada from the H1N1 flu virus have been relatively mild. If there's excessive use of antivirals in the population, the viruses can begin to adapt and develop resistance, which means the drugs are no longer effective in treating the illness.

That's why the Public Health Agency of Canada (PHAC) and Canada's Chief Public Health Officer, Dr. David Butler-Jones, is recommending the prudent use of antivirals in treating the H1N1 flu virus. PHAC recommends that antivirals be used to treat people who have more severe illness, not people who are only mildly ill. Treatment is also recommended for anyone who is at high-risk of complications of seasonal influenza.

Additionally, some people are wondering if they should take antivirals to prevent them from getting sick. This is called prophylaxis. At this point, the Agency has not changed its recommendations for the use of antivirals as prophylaxis for influenza. PHAC recommends that antivirals be used to prevent the spread of illness in closed settings, such as hospitals and long-term care facilities. PHAC does not recommend that family members and other close contacts of people who are sick with the H1N1 flu virus take antivirals as a preventative measure.

Canada has a national antiviral stockpile of 55 million doses, made up of both Tamiflu and Relenza. This stockpile is stored in secure sites across the country, and has been distributed to provinces and territories on a per-capita basis.  The Government of Canada also has additional amounts held in the National Emergency Stockpile as back-up, if needed.

All medications should be used judiciously and only when needed.  All drugs have benefits and side effects and it is important to use medications appropriately and where needed. This is particularly true of our antiviral stockpile of drugs.  They are a finite resource.  The Government of Canada wants to be certain they will not run out before they are really needed.

As with all prescription medications, the decision about what drugs to prescribe and when to prescribe them is made by the patient's doctor after a thorough examination and consideration of the severity of symptoms.  If you have concerns, you should talk to your healthcare professional.

Antivirals are a treatment option, but the most effective way to reduce the impact of an influenza outbreak is to take measures to prevent you from getting sick. Wash your hands, cover coughs and sneezes, avoid close contact with people who are sick, and stay home and avoid others if you are sick. We can all take these simple measures to protect our health and the health of those around us.