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Tamiflu dosage, forms, and strengths

Dosage, forms, and strengths | Tamiflu for adults | Tamiflu for children | Tamiflu dosage chart | Treatment of flu infection | Prevention of flu infection | Tamiflu for pets | How to take Tamiflu | FAQs

Tamiflu (oseltamivir) is a brand-name prescription antiviral medication indicated for the treatment of flu infections in patients ages 2 weeks or older, or prevention in patients at least 3 months of age. Tamiflu works by preventing the flu virus from infecting healthy cells. For most adult patients, Tamiflu is taken for five days as a twice-daily 75 milligram (mg) dose by capsule or oral suspension.

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Tamiflu dosage, forms, and strengths

Most adult patients will take a twice-daily 75 mg dose for five days to treat flu infection. To prevent flu infection, Tamiflu is typically given as a single daily dose of 75 mg dose for 10 days as soon as possible after exposure to the virus. 

  • Capsules: 30 mg, 45 mg, or 75 mg capsules
  • Oral suspension: 6 mg/ml (total 360 mg/60 ml) oral suspension liquid

Adults

For adults and adolescents 13 years of age or older, Tamiflu is usually taken as a fixed twice-daily dose. Children, as well as adult patients with renal impairment, will be given a smaller twice-daily dose. 

  • Standard Tamiflu dosage for adults: 75 mg taken twice daily for five days
  • Maximum Tamiflu dosage for adults: The manufacturer (Genentech/Roche) has not specified a maximum dosage, but the maximum recommended dosage is 150 mg taken twice daily for five days, usually reserved for critically ill patients in the hospital

For patients given Tamiflu to prevent pre- or post-exposure flu infection, a fixed single dose will be taken daily for as long as prophylaxis is needed.

Children

Tamiflu is FDA approved for the treatment of influenza infection in children 2 weeks of age or older who have not had symptoms for longer than 48 hours. Initiation after 48 hours is still recommended for patients with severe illness or at risk for progression to severe illness. Pediatric dosing will be determined by the child’s age, weight, and, for flu treatment, the child’s status as a preterm or at-term birth. Only a very small amount of Tamiflu passes into breast milk, so infants on Tamiflu who are breastfeeding from a mother who is also taking Tamiflu will not require a dose adjustment.

Tamiflu dosage for flu treatment by age for children
Age Recommended dosage
Preterm infants
Less than 38 weeks postmenstrual age 1 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Maximum: 1 mg per kg of body weight twice daily for 5 days
38-40 weeks postmenstrual age 1.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Maximum: 1.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Greater than 40 weeks postmenstrual age 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Maximum: 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Term infants
Less than 8 months 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Maximum: 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
9-11 months 3.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
Maximum: 3 to 3.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
1-12 yrs (less than or equal to 15 kg/33 lbs) 30 mg twice daily for 5 days
Maximum: 30 mg twice daily for 5 days
1-12 yrs (15.1-23 kg/33-50 lbs) 45 mg twice daily for 5 days
Maximum: 45 mg twice daily for 5 days
1-12 yrs (23.1-40 kg/50-88 lbs) 60 mg twice daily for 5 days
Maximum: 60 mg twice daily for 5 days
1-12 yrs (greater than 40 kg/88 lbs) 75 mg twice daily for 5 days
Maximum: 75 mg twice daily for 5 days
13-17 yrs 75 mg twice daily for 5 days
Maximum: 75 mg twice daily for 5 days

Tamiflu is also FDA approved to prevent flu infection in children greater than 1 year of age, but is recommended by the American Academy of Pediatrics to prevent flu infection in children 3 months or older who are hospitalized or at risk for complications. Again, the dosage will be determined by both the child’s age and weight.

Tamiflu dosage for flu prevention by age for children
Age Recommended dosage
3-8 months 3 mg per kg (2.2 lbs) of body weight once daily for at least 10 days
Maximum: 3 mg per kg (2.2 lbs) of body weight once daily for 6 weeks
9-11 months 3.5 mg per kg (2.2 lbs) of body weight once daily for 10 days
Maximum: 3 to 3.5 mg per kg (2.2 lbs) of body weight once daily for 6 weeks
1-12 yrs (less than or equal to 15 kg/33 lbs)) 30 mg once daily for 10 days
Maximum: 30 mg once daily for 6 weeks
1-12 yrs (15.1-23 kg/33-50 lbs) 45 mg once daily for 10 days
Maximum: 45 mg once daily for 6 weeks
1-12 yrs (23.1-40 kg/50-88 lbs) 60 mg once daily for 10 days
Maximum: 60 mg once daily for 6 weeks
1-12 yrs (greater than 40 kg/88 lbs) 75 mg once daily for 10 days
Maximum: 75 mg once daily for 6 weeks
13-17 yrs 75 mg once daily for 10 days
Maximum: 75 mg once daily for 6 weeks
*6 weeks of prophylaxis would only be warranted in specific scenarios; 10 days of prophylaxis is the standard

 

Tamiflu dosage chart
Indication Age Weight Standard dosage Maximum dosage
Influenza treatment (Preterm)
<38 weeks postmenstrual age
1 mg per kg (2.2 lbs) of body weight twice daily for 5 days  1 mg per kg (2.2 lbs) of body weight twice daily for 5 days
(Preterm)
38-40 weeks postmenstrual age
1.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days 1.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
(Preterm)
>40 weeks postmenstrual age
3 mg per kg (2.2 lbs) of body weight twice daily for 5 days 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
(Term) <8 months 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days 3 mg per kg (2.2 lbs) of body weight twice daily for 5 days
9-11 months 3.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days 3.5 mg per kg (2.2 lbs) of body weight twice daily for 5 days
1-12 yrs <15 kg/33 lbs 30 mg twice daily for 5 days  30 mg twice daily for 5 days
1-12 yrs 15.1-23 kg/33-50 lbs 45 mg twice daily for 5 days 45 mg twice daily for 5 days
1-12 yrs 23.1-40 kg/50-88 lbs 60 mg twice daily for 5 days  60 mg twice daily for 5 days
1-12 yrs >40 kg/88 lbs 75 mg twice daily for 5 days  75 mg twice daily for 5 days
13-17 yrs 75 mg twice daily for 5 days 75 mg twice daily for 5 days
Adults 18 yrs or older 75 mg twice daily for 5 days Not specified
Influenza prevention 3-8 months 3 mg per kg (2.2 lbs) of body weight once daily for 10 days 3 mg per kg (2.2 lbs) of body weight once daily for 6 weeks
9-11 months 3 to 3.5 mg per kg (2.2 lbs) of body weight once daily for 10 days 3 to 3.5 mg per kg (2.2 lbs) of body weight once daily for 6 weeks
1-12 yrs <15 kg/33 lbs 30 mg once daily for 10 days  30 mg once daily for 6 weeks
1-12 yrs 15.1-23 kg/33-50 lbs 45 mg once daily for 10 days 45 mg once daily for 6 weeks
1-12 yrs 23.1-40 kg/50-88 lbs 60 mg once daily for 10 days  60 mg once daily for 6 weeks
1-12 yrs >40 kg/88 lbs 75 mg once daily for 10 days

 

75 mg once daily for 6 weeks
13-17 yrs 75 mg once daily for 10 days 75 mg once daily for 6 weeks
Adults 18 yrs and older 75 mg once daily for 10 days 75 mg once daily for 12 weeks

Tamiflu for treatment of flu infection

Tamiflu is FDA approved for the treatment of flu infection caused by influenza A or influenza B viruses in adults and children older than 2 weeks.

  • Standard Tamiflu dosage for adults: 75 mg taken twice daily for five days.
  • Maximum Tamiflu dosage for adults: Maximum dosage is not specified, but doses of 150 mg twice daily for up to 10 days have been utilized in certain patient populations.
  • Standard Tamiflu dosage for children younger than 13: Dose amount is based on age and weight; taken twice daily for five days.
  • Renally impaired patients (kidney disease)—dose amount adjustment: The active form of Tamiflu, oseltamivir carboxylate, is eliminated by the kidneys, so renal impairment will increase the amount of the active form of Tamiflu in the body.
    • Creatinine clearance of 31-60 ml/min: 30 mg taken twice per day for five days
    • Creatinine clearance of 11-30 ml/min: 30 mg taken once per day for five days
    • Creatinine clearance of 10 ml/min or less: Tamiflu should not be taken.
    • Hemodialysis: (not recommended) 30 mg once, then 30 mg after each dialysis session to complete five days of treatment. 
    • Peritoneal dialysis: (not recommended) 30 mg taken in a single dose.
  • Hepatic impairment (liver disease): Tamiflu is first processed by the liver before it can effectively act against influenza, but no dose adjustments are required in patients with hepatic impairment due to liver damage or hepatitis.
  • Pregnant patients—dose amount adjustment: 
    • Dose may be increased to 105 mg twice per day for five days.
    • For pregnant patients hospitalized with flu complications, the dose may be increased to 150 mg twice per day for five days.
  • Immunocompromised patients—dose amount adjustment: The Centers for Disease Control and Prevention (CDC) recommends that the dose can be increased to 150 mg twice per day for immunocompromised patients.
  • Chronic cardiac and other severe medical conditions: No dose adjustment required.

Tamiflu for prevention of flu infection

Tamiflu is FDA approved for the prophylaxis of influenza infection caused by influenza A or influenza B viruses. As prophylaxis, Tamiflu is indicated only for patients who are at an increased risk of developing complications from influenza infection or who cannot receive the flu vaccine. 

Tamiflu must be taken before or within 48 hours after the patient has been in close contact with an infected individual to have its greatest effect. The drug is typically taken as a single daily dose for 10 days, but the duration can continue as long as six weeks during community outbreaks. Patients who are immunocompromised can be given Tamiflu as prophylaxis for up to 12 continuous weeks.

  • Standard Tamiflu dosage for adults: 75 mg taken once daily for at least 10 days and up to six weeks (safety for up to twelve weeks has been proven).
  • Maximum Tamiflu dosage for adults: Maximum dose is not specified.
  • Standard Tamiflu dosage for children younger than 13: Dose amount is based on age and weight; taken once daily for at least 10 days and up to six weeks days.
  • Renally impaired patients (kidney disease)—dose amount adjustment: The active form of Tamiflu, oseltamivir carboxylate, is eliminated by the kidneys, so renal impairment will lengthen the amount of time Tamiflu is active in the body.
    • Creatinine clearance of 31-60 ml/min: 30 mg taken once per day.
    • Creatinine clearance of 11-30 ml/min: 30 mg taken once every two days.
    • Creatinine clearance of 10 ml/min or less: Tamiflu should not be taken. 
    • Hemodialysis: (not recommended) 30 mg once, then 30 mg after each dialysis session to complete 5 days of treatment.
    • Peritoneal dialysis: (not recommended) 30 mg taken once weekly for the duration of prophylaxis.
  • Hepatic impairment (liver disease): Tamiflu is first processed by the liver before it can effectively fight off the influenza virus, but the manufacturer has not specified a reduced dose for patients with liver problems (hepatic impairment).
  • Chronic cardiac and other severe medical conditions: No dose adjustment required.

Tamiflu for pets

The use of Tamiflu in animals has not been approved by the FDA. However, some veterinarians may prescribe Tamiflu or generic oseltamivir to treat or prevent influenza infection in dogs, but this use of Tamiflu is discouraged. 

More commonly, veterinarians may use oseltamivir to treat other viral infections such as parvovirus, Bordetella (kennel cough), or distemper in dogs as well as calicivirus, a viral respiratory disease in cats. These infections have no cure and can produce fatal outcomes. Tamiflu may be effective against parvovirus by inhibiting intestinal bacterial infections. The potential role remains speculative. However, its ability to treat Bordetella, distemper, and calicivirus are disputed. Because oseltamivir is not approved for animal use and very little research has been conducted on animals, there is no standard Tamiflu dose for animals. 

How to take Tamiflu

Tamiflu is taken by mouth in a fixed-dose once or twice per day for a fixed period of time.

  • Your doctor will tell you how much medicine to use. Do not use more than directed. Do not take this medicine for any illness other than the flu.
  • Start taking this medicine as soon as possible after flu symptoms begin or within two days after being exposed to influenza.
  • Tamiflu can be taken with or without food.

Storage

  • Store the medicine in a closed container at room temperature away from heat, moisture, and direct light. 
  • While the oral suspension can be stored at room temperature, it must be used within 10 days. It’s better to store the oral suspension in the refrigerator (36˚-46˚), but it must be used within 17 days. Do not freeze. Safely dispose of any medicine that has not been used within this time.

Capsule

  • Swallow the capsule whole with a glass of water. Do not crush or chew it.
  • You may open the capsule and mix the contents with a sweet liquid (such as chocolate syrup, corn syrup, or sugar dissolved in water). Ask a healthcare provider if you have any questions.

Oral liquid

  • Measure the liquid medicine with the oral syringe or metered dispenser that came with the medicine. Ask your pharmacist for a measuring syringe if you do not have one.
  • Shake the closed bottle well before each use.
  • Remove the cap from the bottle. 
  • Make sure the syringe adapter has been pushed into the bottle opening. If not, fully insert the syringe adapter into the bottle opening.
  • Push the syringe plunger all the way down to the tip.
  • Insert the syringe tip into the adapter.
  • Turn the bottle and syringe upside down.
  • Slowly draw out enough liquid to the correct milliliter mark.
  • Turn the bottle back to the upright position.
  • Remove the syringe and place the tip in the mouth.
  • Slowly empty the contents into the mouth and swallow.
  • Securely fasten the child-safety cap back on the bottle.

Missed dose

  • If you miss a dose and your next dose is due within two hours, skip the missed dose and take your medicine at the normal time. Do not use extra medicine to make up for a missed dose. If you miss a dose and your next dose is due in more than two hours, take the missed dose as soon as you can. Then take your next dose at the normal time and go back to your regular schedule.

When taking Tamiflu, you may want to consider the following safety and effectiveness tips:

  • Before taking Tamiflu, please read the Medication Guide that comes with it. Ask your pharmacist for a copy if you do not have one.
  • Always check the expiration date. If the medicine has passed its expiration date, dispose of it safely and purchase a replacement.
  • Keep a regular, easily-remembered time of day to take each dose, such as wake-up time and after dinner. You can also use telephone apps or alarms to signal when a dose needs to be taken.
  • If taking Tamiflu causes stomach upset or other gastrointestinal problems, try taking it with food.

Tamiflu dosage FAQs

How long does it take Tamiflu to work?

Tamiflu shortens the duration of flu symptoms (sore throat, fever, fatigue, headache, or stuffy nose) by an average of one day or less. Most people taking oseltamivir should notice an improvement in flu symptoms in about six days. However, when taken as prophylaxis of influenza, the effects of Tamiflu will not be noticeable. However, Tamiflu does significantly decrease the risk of contracting symptomatic influenza.

How long does Tamiflu stay in your system?

Tamiflu will stay in the system about 30 to 50 hours after taking the last dose. Oseltamivir phosphate, the active ingredient in Tamiflu, is quickly metabolized by the liver into oseltamivir carboxylate, the form of the drug that works against the flu virus. This active metabolite is detectable within 30 minutes of taking a dose. Oseltamivir carboxylate is then eliminated from the body in the urine. 

Healthcare professionals measure the rate at which the body eliminates Tamiflu by its half-life, that is, the amount of time it takes the body to eliminate half the drug from the bloodstream. For adults, the half-life of oseltamivir phosphate, the form of Tamiflu that doesn’t work, is one to three hours. Oseltamivir carboxylate, the effective form of Tamiflu, has a half-life of 6-10 hours. Generally, a drug is considered to be eliminated from the body after 3-5 half lives have passed. 

What happens if I miss a dose of Tamiflu?

If you miss a dose and your next dose is due within two hours, skip the missed dose and take your medicine at the normal time. Do not take two doses to make up for a missed dose. If you miss a dose and your next dose is due in more than two hours, take the missed dose as soon as you can. Then take your next dose at the normal time and go back to your regular schedule.

How do I stop taking Tamiflu?

Tamiflu is prescribed as a fixed-dose for a limited amount of time, usually five or 10 days. In some cases, however, the duration can stretch to as long as six to 12 weeks during a community outbreak or flu pandemic and based on underlying conditions. Each Tamiflu dose must be taken on schedule for the entire duration. At the end of the prescribed period, you will immediately stop taking Tamiflu. There are no adverse events or withdrawal symptoms when you discontinue Tamiflu. 

If you experience possible side effects of Tamiflu such as a sudden drop in blood pressure (anaphylaxis), allergic reaction, a severe skin reaction (Stevens-Johnson syndrome, toxic epidermal necrolysis, or erythema multiforme), colitis, or signs of abnormal behavior (neuropsychiatric events), stop taking the drug. Tamiflu contains sorbitol and should be discontinued if you have a hereditary fructose intolerance. 

What can be used instead of Tamiflu?

If you can’t take Tamiflu, your doctor may put you on alternative neuraminidase inhibitors such as Relenza (zanamivir) or Rapivab (peramivir). Xofluza (baloxavir marboxil) is a slightly different drug that also treats flu infections by preventing the flu virus from infecting healthy cells.

What is the maximum dosage for Tamiflu?

The manufacturer and the FDA have not specified a maximum dosage or duration for Tamiflu. The standard dose is 75 mg taken once or twice a day for a fixed period of time. For pregnant women who are hospitalized with flu complications, the manufacturer (Genentech/Roche) indicates that the Tamiflu dose can go as high as 150 mg given twice per day.

What interacts with Tamiflu?

Foods do not affect Tamiflu’s absorption or effectiveness. However, if taking Tamiflu causes side effects such as upset stomach, constipation, or diarrhea, changes in the diet may be required.

Oseltamivir does not cause serious adverse events when taken with other drugs. Drug interactions with oseltamivir typically involve increasing or decreasing the concentration of oseltamivir or other drugs in the system, including antiviral medications. If these drug interactions occur, the prescribing physician may need to modify one or more of these treatments. 

Oseltamivir may reduce the effectiveness of an influenza vaccination. Tamiflu should not be taken until at least two weeks after a live attenuated flu vaccine. Alternatively, a live attenuated flu vaccine should not be given until at least 48 hours have passed since the last Tamiflu dose.

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