Oseltamivir or zanamivir
Examples
Generic Name Brand Name oseltamivir phosphate Tamiflu zanamivir Relenza Oseltamivir is taken as a tablet twice each day for 5 days.
Zanamivir is inhaled through a device called a Diskhaler. This inhaler device delivers the medicine to the lungs, where the influenza (flu) virus multiplies. It is inhaled twice a day for 5 days.
How It Works
Zanamivir and oseltamivir 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
Zanamivir and oseltamivir may be used to treat flu caused by both the influenza A and B viruses.
- Both medicines are given twice a day for 5 days.
- Zanamivir is used for people age 7 and older.
- Oseltamivir is used to treat flu in people age 1 or older.
How Well It Works
Both zanamivir and oseltamivir have been shown to effectively treat and prevent the flu.1 Using one of these medicines typically shortens the course of influenza A or B by at least 1 day.1
A well-controlled study found that oseltamivir, taken within 36 hours of the first flu symptoms, reduced the length of illness by 30%, the severity by 40%, and the time to resume normal activities by 2 or 3 days. These results are compared with people who had treatment with a placebo.2
Zanamivir has been shown to prevent flu among household members when a member of the family is infected.3
Zanamivir and oseltamivir 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.
Side Effects
No major side effects have been reported with the use of zanamivir and oseltamivir. Some minor side effects that may occur include:
- Diarrhea.
- Nausea and vomiting. This side effect tends to occur with oseltamivir. Taking the medicine with food may reduce the risk.
- Swelling of the sinuses (sinusitis).
A small number of people showed behaviour changes after they took oseltamivir.4 These include:
- Attempts to hurt themselves.
- Confusion or delirium.
Anyone who takes Tamiflu, especially children, should be watched closely. If the person seems confused, tries to hurt himself or herself, or is acting strangely, call a doctor right away. Health Canada continues to monitor the safety of these medicines and will inform Canadians if new safety information arises.
See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)
What To Think About
To be effective, zanamivir and oseltamivir must be started within 48 hours of when you first notice flu symptoms.
Some people who have asthma or chronic obstructive pulmonary disease (COPD) and use zanamivir may experience reduced lung function and have difficulty breathing. If you have these conditions, talk to your doctor about whether you should use this medicine.
The influenza virus A can develop resistance to the antiviral flu medicines amantadine and rimantadine. Although influenza viruses A and B have not developed resistance to zanamivir or oseltamivir at this time, resistance is possible with increased use of these medicines.
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| Author: | Sydney Youngerman-Cole, RN, BSN, RNC | Last Updated: September 22, 2006 |
| Medical Review: | Adam Husney, MD - Family Medicine W. David Colby IV, MSc, MD, FRCPC - Infectious Disease | |
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| Topic Contents | |
| Examples | |
| How It Works | |
| Why It Is Used | |
| How Well It Works | |
| Side Effects | |
| What To Think About | |
| References | |