Oseltamivir or Zanamivir
Oseltamivir is taken as a pill twice each day for 5 days.
Zanamivir is inhaled through a device called a Diskhaler. This inhaler device delivers the medicine to the lungs, because that is where the influenza (flu) virus multiplies. It is inhaled twice a day for 5 days.
How It Works
Oseltamivir and zanamivir are medicines known as neuraminidase inhibitors. They help prevent influenza A and influenza B viruses from multiplying in the body by interfering with the production and release of virus from cells that line the respiratory tract. This may slow the spread of the infection within the airways and lungs.
Why It Is Used
Oseltamivir and zanamivir may be used to treat flu caused by both the influenza A and B viruses.
The U.S. Food and Drug Administration (FDA) has also approved oseltamivir to prevent flu in adults and children age 13 and older. Zanamivir is approved for use to prevent the flu in adults and children age 5 and older.
How Well It Works
Zanamivir may prevent flu among household members when a member of the family is infected.4
Oseltamivir and zanamivir may not be as effective for people who do not have a fever or do not have severe flu symptoms. And more study is needed to find out how well these medicines work to prevent the flu in people who have severely impaired immune systems.
All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.
Here are some important things to think about:
Call your doctor if you have:
Common side effects of these medicines include:
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
Oseltamivir and zanamivir work best when started within 48 hours of your first flu symptoms.
Some people who have asthma or chronic obstructive pulmonary disease (COPD) and use zanamivir may experience reduced lung function and have trouble breathing. If you have these conditions, talk to your doctor about whether you should use this medicine.
Although influenza viruses A and B have not yet developed resistance to oseltamivir and zanamivir, resistance is possible with increased use of these medicines.
Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.
There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
Advice for women
If you are pregnant, breast-feeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breast-feeding, or planning to get pregnant.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
eMedicineHealth Medical Reference from Healthwise
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