Amantadine or rimantadine for influenza (flu)

Examples

Generic Name	Brand Name
amantadine hydrochloride	Symadine, Symmetrel
rimantadine hydrochloride	Flumadine

How It Works

These antiviral medications prevent the spread of type A influenza by interfering with the production of the virus inside the body. They do not treat or protect you against influenza B.

Why It Is Used

These antiviral medications reduce the severity of influenza (flu) symptoms and shorten the course of the illness of influenza A.¹ They need to be started within 48 hours of the first symptoms and continued, usually, for 7 days.

For the past few years, the U.S. Centers for Disease Control and Prevention (CDC) has advised doctors not to use amantadine (Symadine or Symmetrel) or rimantadine (Flumadine) to treat or prevent the flu. These medicines have not worked against most types of the flu virus. Talk to your doctor about the medicine that is best to use for the current type of flu.

When used to protect people during a flu outbreak, antiviral medications usually are used for 7 days but may be continued for 5 to 7 weeks.

How Well It Works

In healthy young adults and children, antiviral medications are 70% to 90% effective in preventing influenza A during an outbreak.² However, these antiviral medicines do not always treat or prevent the flu.³

When given within 48 hours after symptoms begin, they may reduce symptoms, shorten the length of influenza A illness by 1 or 2 days, and allow for a faster return to usual activities.

Side Effects

In one study, approximately 13% of healthy adults taking amantadine and 6% of those taking rimantadine reported minor side effects, which can include:²

• Sleeplessness (insomnia), dizziness, headache, nervousness, or an inability to concentrate. These side effects occur less often with rimantadine than amantadine. They are more common in people who are also taking antihistamines.
• Nausea, vomiting, loss of appetite (1% to 3%).

More serious but less frequent side effects (seizures, confusion) have been reported in older adults and, most commonly, in adults who have seizure disorders. Lowering the dose reduces these side effects without reducing the effectiveness of the medication.

Side effects decrease after about 1 week of use and reverse as soon as treatment stops.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Amantadine and rimantadine are effective only against some type A influenza viruses.

Amantadine usually should not be taken at the same time as antihistamines or other medications that stimulate the central nervous system. These may increase the risk of side effects such as insomnia, anxiety and, at high doses, seizures.

Amantadine is removed from the body by the kidneys; rimantadine by the liver. This difference may have an impact on which medication is used to treat people who have diseases affecting the kidneys or liver. Because side effects occur less often with rimantadine, it may be a better choice. However, rimantadine costs more than amantadine.

Little information exists regarding the effectiveness of antiviral medications in treating children who have influenza A.

• Amantadine is used to prevent and treat type A influenza in adults and in children older than age 1.
• Rimantadine is used to prevent and treat type A influenza in adults. However, in children, it is used only to prevent influenza A.

Antiviral medications may prevent complications of type A influenza illness in high-risk people; the evidence is not conclusive.⁴

Antiviral medications may need to be given only once a day in older adults.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.

Author:	Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated: September 29, 2006
Medical Review:	Adam Husney, MD - Family Medicine W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.