Three antiviral drugs (amantadine, rimantadine, and oseltamivir) are approved and commercially available for use in preventing flu. All of these medications are prescription drugs, and a doctor should be consulted before the drugs are used. When used for prevention, they are about 70% to 90% effective for preventing illness in healthy adults.
Four antiviral drugs (amantadine, rimantadine, zanamavir and oseltamivir) have been approved for treatment of the flu. If taken within 2 days of getting sick, these drugs can reduce the symptoms of the flu and shorten the time you are sick by 1 or 2 days. They also can make you less contagious to others. All of these drugs must be prescribed by a doctor and taken for 5 days. Antiviral drugs are effective only against influenza viruses. They will not help the symptoms associated with the common cold or many other flu-like illnesses caused by viruses that circulate in the winter.
All of the antiviral drugs are different in terms of who can take them, how they are given, any dosing changes based on age or medical conditions, and side effects. Your doctors will help decide whether you should get antivirals and which one you should get.
Antiviral drugs are most often used to control flu outbreaks in institutions, for example in nursing Homes, or in hospital wards, where people at high risk (see below) for complications from flu are in close contact with each other. antivirals also have been used on cruise ships or similar settings to control outbreaks of the flu.
In the event of an outbreak, public health practice is to combine the use of flu vaccine and antivirals . In a nursing Home during an outbreak, for example, residents and staff are given the flu vaccine and antivirals to prevent flu until the vaccine takes effect (about 2 weeks). This practice continues as long as influenza is occurring in that setting.
Doctors also can prescribe antivirals for flu to people not living in institutional settings, but treatment must begin within 2 days of the onset of symptoms for it to be effective. Also, while all antivirals lessen the symptoms of illness and shorten the duration of illness, only 1 (oseltamivir) has been shown in a study to reduce some complications requiring antibiotics.
When considering antivirals , it’s important to remember that most healthy people recover from the flu without complications.
Some people are considered to be at high risk from complications of flu. This includes
- People 65 years of age and older
- Children 6-23 months of age*
- People of any age with chronic medical conditions (for example, heart or lung disease, diabetes)
- Pregnant women
Note that none of the antivirals are approved for use in children less than 1 year of age.
*Children 6-23 months of age are at increased risk for influenza-related hospitalization.
For Treatment: If you get sick with flu-like symptoms this season, your doctor first may give you a test to find out whether you have influenza. (Symptoms of flu include: fever (usually high), headache, tiredness, a sore throat and dry cough, nasal congestion, and body aches.) Your doctor also will consider a number of things before making a treatment decision, such as your risk for complications from flu.
For Prevention: In the event of a flu outbreak in a Home, institution, or community, your doctor may choose to give antivirals to you as a preventive measure, especially if you are at high risk for complications from the flu. Also, if you are in close contact with someone who is considered at high risk for complications from flu, you may be given antiviral drugs to prevent passing flu to the high-risk person.
Among some healthy adults and children, side effects can include central nervous system (CNS) side effects such as nervousness, anxiety, difficulty concentrating, and lightheadedness, and gastrointestinal side effects like nausea and loss of appetite. CNS side effects happen more often among persons taking amantadine than among persons taking rimantadine. Among some other persons with long-term illnesses, more serious side effects, such as delirium, hallucinations, agitation, and seizures, can occur. Side effects usually diminish and disappear after 1 week.
This drug is inhaled and can cause side effects, especially in those with asthma or other chronic lung disease. Decreased respiratory function and bronchospasm have been reported with use of zanamivir. Zanamivir is generally not recommended for use in persons with underlying lung disease such as asthma and chronic obstructive pulmonary disease. Other side effects reported by less than 5% of those who have used this drug are diarrhea, nausea, sinusitis, nasal infections, bronchitis, cough, headache, and dizziness.
The side effects reported most often in those people who took this drug were gastrointestinal (i.e., nausea and vomiting). Nausea and vomiting may be less severe if oseltamivir is taken with food.
Click on the link below for more detailed information about antiviral drugs for influenza:
Prevention and Control of Influenza, Recommendations of the Advisory Committee on Immunization Practices (ACIP) Morbidity and Mortality Weekly Report (MMWR), April 25, 2003 / Vol. 52 / No. RR-08.
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