Medications Directory

Approved indications: Rimantadine by mouth is approved to treat and prevent illness caused by influenza A virus in adults 17 years and older, and to prevent influenza A in children 1–16 years old; it does not treat influenza B or other respiratory viruses.

Off-label uses and current role: Some specialists have used rimantadine off-label to treat influenza A in children, but this is not an FDA-approved indication. Because most currently circulating influenza A strains are resistant to adamantane drugs (amantadine and rimantadine), major guidelines in the United States generally recommend newer antivirals (such as oseltamivir, zanamivir, or baloxavir) instead, so rimantadine is now rarely chosen in routine care.

Efficacy expectations (when the virus is susceptible): When started within about 48 hours of symptom onset and the influenza A strain is susceptible, rimantadine can shorten the duration of flu symptoms by roughly a day and lessen fever and overall severity; when used for prophylaxis against susceptible strains, it can substantially reduce the chance of developing clinical influenza after exposure. However, because resistance is now common, its real-world effectiveness against current influenza A infections is expected to be low, and neuraminidase inhibitors or other modern antivirals are generally more reliable choices.

Typical adult dosing: For treatment of influenza A in adults 17 years and older, the usual oral dose is 100 mg twice daily for about 5–7 days, started as soon as possible and ideally within 48 hours of symptom onset. For prophylaxis in adults, the typical dose is also 100 mg twice daily for the duration recommended by the prescriber (often from several days up to about 6 weeks in high-risk exposure situations).

Dosing adjustments: In older adults (especially those 65 years and older), and in people with severe kidney or liver impairment, the dose is generally reduced to 100 mg once daily for both treatment and prophylaxis to limit side effects. In children 1–9 years old receiving prophylaxis, a common regimen is 5 mg/kg once daily (maximum 150 mg per day), while children 10 years and older often receive the adult dose; safety and effectiveness for treatment of active influenza in children under 17 years have not been established in the U.S. product labeling.

How to take it: Rimantadine is taken by mouth as tablets or oral liquid, usually in 1 or 2 divided doses daily, and may be taken with food or milk to lessen stomach upset. Take it at evenly spaced times each day, swallow tablets with a glass of water, and follow any special instructions on the prescription label or from your pharmacist, especially for liquid preparations.

Special dosing instructions: Your prescriber may shorten or extend the course depending on how long you have symptoms or remain exposed to influenza. Dose adjustments may be needed if your kidney function changes, if you develop troublesome side effects, or if you start or stop certain other medicines; do not change the dose on your own without medical advice.

Missed dose: If you miss a dose, take it as soon as you remember unless it is almost time for your next scheduled dose; if it is close to the next dose, skip the missed one and resume your regular schedule, and do not take two doses at once to make up for a missed dose.

Overdose: In suspected overdose, serious symptoms can include severe agitation, hallucinations, marked confusion, abnormal heart rhythms, or seizures; emergency medical care and contact with a poison control center (in the U.S., 1-800-222-1222) are essential, and treatment focuses on supportive care and managing complications.

Common side effects: The most frequent side effects involve the stomach and nervous system, including nausea, vomiting, loss of appetite, abdominal pain, dry mouth, insomnia, headache, dizziness, nervousness, fatigue, and difficulty concentrating; these are usually mild to moderate, tend to appear early in treatment, and often improve if the dose is lowered or the drug is stopped.

Serious or rare adverse effects: Less commonly, rimantadine can cause severe allergic reactions (rash, hives, swelling of the face or throat, trouble breathing), marked confusion, mood or behavior changes, hallucinations, severe dizziness or fainting, seizures, or heart rhythm changes; any of these require immediate medical attention and stopping the drug unless a clinician advises otherwise.

Warnings and precautions (medical conditions and special groups): Use rimantadine with caution and often at reduced doses in older adults and in people with significant kidney or liver impairment, because higher blood levels increase the risk of side effects. People with a history of seizures are at higher risk for convulsions, especially if doses are high or antiseizure medicines are changed, so careful monitoring is needed. In pregnancy, rimantadine is generally avoided unless the expected benefit clearly outweighs potential risks to the fetus. It passes into breast milk and is not recommended for nursing mothers. The drug is not approved to treat symptomatic influenza in children under 17 years, and its use for prophylaxis is limited to children 1–16 years under medical supervision.

Comparative safety: Compared with the related drug amantadine, rimantadine tends to cause fewer central nervous system side effects such as confusion and hallucinations, but modern influenza antivirals (like oseltamivir) are usually preferred today because they work against both influenza A and B and are effective against current circulating strains.

Reporting side effects and safety updates: Patients in the United States can report suspected side effects to the FDA MedWatch program (online or by calling 1-800-FDA-1088) and can check the FDA website or medication guides for up-to-date safety alerts and communication about rimantadine and other influenza antivirals.

Drug interactions (prescription and OTC medicines): Rimantadine can interact with the live attenuated intranasal influenza vaccine, reducing the vaccine’s effectiveness, so it is generally avoided for at least 48 hours before and 2 weeks after receiving the nasal flu vaccine. Aspirin and acetaminophen may modestly lower rimantadine blood levels, which could slightly reduce its antiviral effect, though this is usually not clinically significant. Always let your clinician and pharmacist know about all prescription drugs, over-the-counter medicines, and supplements you take so potential interactions can be checked.

Alcohol, supplements, and foods: No specific food interactions are known, and rimantadine can be taken with or without food, but taking it with food or milk may reduce stomach upset. Alcohol can worsen dizziness, drowsiness, and concentration problems caused by rimantadine, so limiting or avoiding alcohol while taking this medicine is recommended.

Precautions and situations where use may be unsafe: Rimantadine should not be used in people with a known allergy to rimantadine, amantadine, or other adamantane drugs. Use with caution in individuals with seizure disorders, significant kidney or liver disease, or in frail older adults, and dose reductions are often needed in these groups. It is generally avoided in pregnancy unless clearly needed and is not recommended while breastfeeding because it passes into breast milk and animal data suggest harm to nursing offspring.

Vaccines and diagnostic procedures: The main interaction of concern is with the live intranasal influenza vaccine; inactivated (injected) flu vaccines do not have this interaction and can be given while on rimantadine. No specific interactions with imaging contrast agents or common diagnostic procedures are expected.

Monitoring needs: Before and during treatment, clinicians may check kidney and sometimes liver function, especially in older adults or those with known organ impairment, and will monitor for central nervous system or gastrointestinal side effects and for any change in seizure control in people with epilepsy.

Q: Does rimantadine still work for the flu today?
A: Rimantadine can work against certain older strains of influenza A, but most currently circulating influenza A viruses in the United States are resistant, so this drug is now rarely used and newer antivirals such as oseltamivir or baloxavir are usually preferred.

Q: How soon should I start rimantadine if I get flu symptoms?
A: For treatment, rimantadine should be started as early as possible, ideally within 48 hours of the first flu symptoms, because its benefit in shortening illness and reducing severity is greatest when begun promptly.

Q: Can children take rimantadine?
A: In the United States, rimantadine is approved to prevent influenza A in children 1–16 years old, using weight-based dosing, but it is not approved to treat active flu illness in this age group, and decisions about its use in children should be made by a pediatric clinician.

Q: Is rimantadine safe in pregnancy or while breastfeeding?
A: Rimantadine is generally avoided in pregnancy unless the expected benefit clearly outweighs potential risks, and it is not recommended while breastfeeding because it enters breast milk and animal studies have shown harm to nursing offspring.

Q: What should I avoid while taking rimantadine?
A: Avoid the live intranasal flu vaccine from 48 hours before until 2 weeks after rimantadine therapy, limit alcohol because it can worsen dizziness and confusion, and use caution with activities that require alertness—such as driving—until you know how the medicine affects you.

Storage: Store rimantadine tablets or oral liquid at room temperature (about 68–77°F / 20–25°C), protected from excessive heat, moisture, and direct light, and keep the bottle tightly closed and out of reach of children and pets; do not freeze the liquid.

Liquid shelf-life: Use oral liquid only for the period specified on the label (commonly up to 14 days at room temperature) and discard any remaining medicine after that time.

Disposal: Do not keep unused or expired rimantadine; use a community drug take-back program if available, or ask your pharmacist or local waste authority how to dispose of it safely, and do not flush it down the toilet unless you are specifically instructed to do so.