Flumadine (Rimantadine): Side Effects and Why It's No Longer Recommended for Flu
Medically reviewed by Lauren Okafor | MD on August 23rd, 2026 and Alan Lucks | MD on November 4th, 2026.
Published on March 3rd, 2026.
Key Takeaways
The CDC does not recommend rimantadine for flu because circulating influenza A viruses are resistant; ask about oseltamivir or baloxavir instead.
Common side effects include nausea, dizziness, and insomnia, but serious side effects are rare.
Kidney or liver problems may mean you need a lower dose or can't take rimantadine, so always tell your doctor about your medical history.
Rimantadine may interact with other medications, so discuss all your current drugs with your doctor.
Flumadine (Rimantadine) Overview: Not Recommended for Flu
Rimantadine was used for influenza A, but the CDC no longer recommends it because circulating influenza A viruses are resistant. It belongs to a drug class called adamantanes. It was designed to block influenza A from copying itself, but today's influenza A strains have changes that stop it working.
It was also once used to prevent flu after exposure, but the CDC no longer recommends it for prevention either. It's taken by mouth as a tablet or liquid and travels through your bloodstream to your airways, where flu viruses live.
What to Take Instead of Rimantadine
The CDC recommends 4 flu antivirals instead of rimantadine: oseltamivir, baloxavir, zanamivir and peramivir. They differ in how and how often you take them, so the right one depends on you.
Tamiflu (oseltamivir): An oral capsule or liquid, taken twice a day for 5 days at home. It's the preferred antiviral in pregnancy.
Xofluza (baloxavir): A single oral dose. It suits people who would rather take one dose than a multi-day course.
Relenza (zanamivir): An inhaled powder, used twice a day for 5 days. It isn't a good fit for people with breathing conditions such as asthma.
Rapivab (peramivir): A single IV infusion given in a clinic or hospital. It suits people who can't take medicine by mouth.
Flu antivirals work best when started early, ideally within 48 hours of your first symptoms. A licensed doctor can tell you which option fits your health and history. You can get a current flu antiviral prescribed online through a video visit on Doctronic.
For a closer look at how each one works, read about the 4 FDA-approved flu antivirals.
Side Effects
Most people tolerate rimantadine well, especially when taken at recommended doses. Side effects range from mild to serious, and most mild effects fade as your body adjusts to the medication.
Common Side Effects
Nausea and vomiting: Your stomach may feel unsettled, particularly if you take the medicine without food. Eating a light meal can help reduce this effect.
Dizziness or lightheadedness: You may feel off-balance or faint, especially when standing up quickly. Move slowly and sit down if you feel dizzy.
Insomnia or sleep problems: Rimantadine can stimulate your nervous system, making it harder to fall asleep or stay asleep. Try taking your dose earlier in the day.
Nervousness or anxiety: Some people feel jittery or on edge while taking this medication. This usually improves after a few days.
Loss of appetite: You may not feel hungry, which can make nausea worse if you skip meals.
Headache: A mild to moderate headache may develop, similar to a tension headache.
Serious Side Effects
Confusion or hallucinations: In rare cases, especially in elderly patients, rimantadine can cause mental changes. Stop taking the drug and call your doctor immediately if this happens.
Difficulty breathing: Shortness of breath or wheezing could indicate a serious problem. Seek immediate medical attention if you experience this.
Severe allergic reaction: Rash, swelling of the face or throat, or difficulty breathing require emergency care.
Seizures: Uncontrolled electrical activity in the brain is uncommon but serious. Call 911 if a seizure occurs.
Heart rhythm problems: Irregular heartbeat or palpitations should be reported to your doctor urgently.
When to Seek Medical Attention
Most side effects from rimantadine are mild and go away on their own. However, contact your doctor if side effects persist for more than a few days, worsen, or interfere with your daily life. You should seek immediate medical attention if you experience confusion, severe allergic reactions, difficulty breathing, chest pain, or any signs of a seizure. Don't wait. Call your doctor or go to the emergency room if you're unsure whether your symptoms warrant urgent care.
Label Dosage (For Reference Only)
Dose Level or Form |
Dose |
Key Detail |
|---|---|---|
Adult Treatment |
100 mg twice daily |
Start within 48 hours of symptom onset; continue for 5-7 days |
Adult Prevention |
100 mg once or twice daily |
Use during exposure periods or flu season; duration varies |
Elderly Patients |
100 mg once daily |
Reduced dose due to increased sensitivity; consult doctor |
Kidney Impairment |
100 mg once daily |
Dose reduced if creatinine clearance is low; doctor will adjust |
Children (1-9 years) |
5 mg/kg per day (liquid form) |
Weight-based dosing; do not exceed 150 mg per day |
Children (10+ years) |
100 mg twice daily |
Same as adult dosing once child reaches 10 years old |
These are the labeled doses, shown for reference. Rimantadine isn't recommended for flu today. If you were prescribed it, ask a licensed doctor about a current antiviral.
Drug Interactions
Rimantadine can interact with other medications you may be taking, potentially reducing effectiveness or increasing side effects. Always inform your doctor about all supplements, vitamins, and over-the-counter drugs you use.
Anticholinergic Medications
Anticholinergic drugs (used for conditions like overactive bladder or Parkinson's disease) may increase your risk of nervousness, confusion, or dizziness when combined with rimantadine. Your doctor may adjust doses or monitor you more closely.
Live Influenza Vaccine
Taking rimantadine with the live flu nasal spray vaccine can reduce the vaccine's effectiveness. Space the vaccine at least 2 weeks before or 48 hours after rimantadine to allow the vaccine to work properly.
NSAIDs (Ibuprofen, Naproxen)
Nonsteroidal anti-inflammatory drugs may increase stomach upset or nausea when combined with rimantadine. Take these medicines with food, or ask your doctor if acetaminophen is a safer choice.
Amantadine or Other Antivirals
Using rimantadine with Symmetrel (amantadine) or similar antivirals can increase side effects without improving results. Your doctor will prescribe only one antiviral at a time.
Trimethoprim
This antibiotic can reduce how quickly your kidneys clear rimantadine from your body, raising drug levels in your blood. Your doctor may monitor kidney function or adjust rimantadine's dose.
Frequently Asked Questions
Get answers to common questions about Flumadine and generic rimantadine.
No. The CDC does not recommend rimantadine to treat or prevent flu, because circulating influenza A viruses are resistant to it. It also never worked against influenza B. The recommended options are oseltamivir, baloxavir, zanamivir and peramivir, and a licensed doctor can help you choose one.
Tamiflu is the better choice. It's a CDC-recommended flu antiviral that works against both influenza A and B, while rimantadine isn't recommended. Tamiflu works best when you start it early, and a licensed doctor can prescribe it.
Against older influenza A strains, rimantadine eased fever and aches within a day or two. Today's influenza A viruses are resistant to it, so it isn't expected to shorten flu. If you think you have flu, ask a licensed doctor about oseltamivir or baloxavir. They work best when started within 48 hours of your first symptoms.
Not recommended for flu; oseltamivir is the preferred antiviral in pregnancy. Influenza during pregnancy can lead to serious complications, making antiviral treatment important. If you're pregnant and think you have flu, ask a licensed doctor about oseltamivir as soon as possible.
If you miss a dose, take it as soon as you remember, unless it's almost time for your next scheduled dose. Never double up on doses to make up for a missed one, as this increases the risk of side effects. Rimantadine isn't recommended for flu, so if you're still taking it, ask a licensed doctor whether to switch.
Yes. The live influenza nasal spray vaccine (FluMist) can be less effective if you're taking rimantadine. Get the live vaccine at least 2 weeks before rimantadine, or wait at least 48 hours after your last dose. The inactivated flu shot (injection) is safe to use with rimantadine and is actually the preferred vaccine during antiviral treatment.
Dizziness and nausea occur because rimantadine affects your nervous system and stomach. These side effects usually improve within a few days as your body adjusts. Taking your dose with food can reduce nausea. Stand up slowly and sit down if you feel dizzy. If these effects persist or worsen, contact your doctor.
Still have questions?
A licensed doctor can answer them by video visit on Doctronic, any hour.
The Bottom Line
Rimantadine (Flumadine) was once used for influenza A, but the CDC no longer recommends it. Circulating influenza A viruses are resistant to it, and it never worked against influenza B.
Ask a licensed doctor about oseltamivir or baloxavir instead.
Rimantadine's common side effects are nausea, dizziness, and insomnia. People with kidney or liver disease may need a lower dose or may not be able to take it.
This information is educational and does not replace advice from a licensed doctor.
Think you have flu? Doctronic's medical AI can help you understand your options, for free. It has already helped millions of people. You can also connect with a licensed doctor by video visit ($39) in minutes, any hour, with $19 follow-ups.
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