Influenza Antivirals

Click here for a PDF “print-friendly” version of this fact sheet

What are they?

Influenza antiviral medications are drugs that suppress the ability of influenza viruses to reproduce. When used correctly, they can reduce the duration of symptoms and some complications from influenza virus infection. Antiviral medications are used to prevent and treat influenza. They are most often used to control flu outbreaks in institutions, such as nursing homes or hospitals, where people at high risk for complications from flu are in close contact with each other. The antiviral drugs approved for influenza in Canada are prescription drugs.

How do I access Antivirals?

Antivirals must be prescribed by a physician. If you are unable to receive the influenza vaccine, and your situation indicates that you may require antiviral therapy, talk to your family doctor about obtaining a prescription so you can be prepared in advance. Talk to your pharmacist about the specific details of treatment and possible side effects.

Tamiflu™ (Oseltamivir)

Tamiflu is one of a new class of antiviral drugs called neuraminidase inhibitors. Neuraminidase inhibitors attack the influenza virus and stop it from spreading inside your body. As the flu virus takes hold in the body, it forms new copies of itself and spreads from cell to cell. Neuraminidase inhibitors fight the virus by preventing the release of new copies from infected cells. Tamiflu can prevent the flu as long as you continue taking this medication, but getting a yearly influenza vaccination is still the best way of preventing the disease. For older adults, healthcare workers, and people with an immune deficiency or respiratory disease, vaccination remains a must.

Tamiflu is also indicated for the ‘prevention’ of influenza in adults and adolescents 13 years and older, and ‘treatment’ of uncomplicated influenza A and B in patients one year of age and older.  It must be started within 48 hours of onset of symptoms.

Who should take them?

People who are at high risk of serious complications from influenza may benefit most from antiviral medications. Therefore, in general, people who fall into these high-risk groups should be given priority for use of influenza antiviral medications:

• Any person experiencing a potentially life-threatening influenza-related illness should be treated with antiviral medications.
• Any person at high risk for serious complications of influenza and who is within the first 2 days of illness onset should be treated with antiviral medications. (Pregnant women should consult their primary provider regarding use of influenza antiviral medications.)
• All persons who live or work in institutions caring for people at high risk of serious complications of influenza infection should be given antiviral medications in the event of an institutional outbreak. This includes nursing homes, hospitals, and other facilities caring for persons with immunosuppressive conditions, such as HIV/AIDS.
• All persons at high risk of serious influenza complications should be given antiviral medications if they are likely to be exposed to others infected with influenza. For example, when a high-risk person is part of a family or household in which someone else has been diagnosed with influenza, the exposed high-risk person should be given chemoprophylaxis.

Antiviral medications can be considered in other situations when the available supply of such medications is locally adequate.

• Persons at high risk of serious complications who are not able to get vaccinated.
• Persons at high risk of serious complications who have been vaccinated but have not had time to mount an immune response to the vaccine. In adults, chemoprophylaxis should occur for a period of 2 weeks after vaccination. In children aged <9 years, chemoprophylaxis should occur for 6 weeks after the first vaccination, or 2 weeks after the second vaccination, depending on whether the child is scheduled to receive one or two doses of vaccine.
• Persons with immunosuppressive conditions who are not expected to mount an adequate antibody response to influenza vaccine.
• Health-care workers with direct patient care responsibilities that are not able to obtain vaccine.

How long should antiviral drugs be taken?

How long antiviral drugs should be taken depends on how they are being used. To prevent influenza, antiviral drugs should be taken for as long as influenza viruses are circulating in a given setting. For example, antiviral medications would be taken for the duration of outbreak activity in a nursing home. This could last for several weeks, depending on the extent of the outbreak. To treat influenza, individuals must take an antiviral within 2 days of onset of illness and continue taking the medication for 5 days.

Can an antiviral cure the flu?

No. When used correctly, antiviral medications can reduce symptoms, shorten the time you are sick by 1 or 2 days, and make you less contagious to others. However, antiviral drugs do not cure the flu outright but they can speed recovery from the flu.

Can influenza antiviral drugs help with other illnesses such as the common cold?

No. Influenza antiviral drugs are effective only against influenza viruses. They will not help reduce symptoms associated with the common cold or many other flu-like illnesses caused by viruses that circulate in the winter.

Before taking TAMIFLU™ consult with your doctor or health care provider if you:

• are taking any other medications
• have any type of kidney disease
• are trying to become pregnant, are already pregnant, or are breast-feeding
• have had any previous reaction to TAMIFLU™ (oseltamivir phosphate)

Treatment

The adult treatment dose is a 75 mg capsule twice daily for 5 days. TAMIFLU™ is excreted through the kidney therefore dosage adjustment is required for people with renal problems. It is recommended that the treatment dose be reduced in persons with creatinine clearance less than 30 mL/min.

Possible Side Effects

People may experience nausea and vomiting after taking the first dose, but it is usually mild and short lived. Taking TAMIFLU™ with food may reduce the potential for these side effects. Other less common side effects may include bronchitis, sleeplessness and vertigo.

Patient information:

• Follow the instructions on the label of the medicine or as directed by your doctor.
• Start to use the medicine as soon as possible after the flu symptoms start to get the most benefit.
• Complete the five-day course and don't miss any doses.
• Antibiotics are only useful for treating bacterial infections. Because the flu is a viral infection, it cannot be treated with antibiotics.
• TAMIFLU™  has not been shown to treat flu-like illnesses caused by any virus other than influenza A and B (e.g. viral gastroenteritis (norovirus), common cold, or other respiratory illnesses not caused by influenza).

Other kinds of infections can appear like influenza or occur along with influenza, and need different types of treatment.  Contact your health care provider if you feel worse or develop new symptoms during or after treatment, or if your influenza symptoms do not start to get better.

Some Differences between a cold and the flu:

• The flu is likely to keep you in bed feeling very exhausted, while a cold makes you feel tired but you can usually get out of bed.
• The flu is more likely to give you a high temperature and a headache than a cold.
• Body aches and pains can be quite severe with the flu whereas with a cold they are very minor or not at all.

Antivirals are not a substitute for the influenza shot.  The influenza vaccine should be given annually in October/early November before influenza season starts. 

For information, check the Health Unit website at www.publichealthgreybruce.on.ca or telephone 519-376-9420 or 1-800-263-3456.