oseltamivir

Generic Name: oseltamivir (os el TAM ih veer)
Brand Names: Tamiflu

What is oseltamivir?

Oseltamivir is an antiviral medication that blocks the actions of influenza virus types A and B in your body.

Oseltamivir is used to treat flu symptoms caused by influenza virus in patients who have had symptoms for less than 2 days. Oseltamivir may also be given to prevent influenza in people who may be exposed but do not yet have symptoms. Oseltamivir will not treat the common cold.

It is dangerous to purchase oseltamivir on the Internet or from vendors outside of the United States. Medications distributed from Internet sales may contain dangerous ingredients, or may not be distributed by a licensed pharmacy. Samples of "Tamiflu" purchased on the Internet have been found to contain cloxacillin, a type of antibiotic that can have dangerous side effects in people who are allergic to penicillin. For more information, contact the U.S. Food and Drug Administration (FDA) or visit www.fda.gov/buyonlineguide.

Oseltamivir may also be used for purposes not listed in this medication guide.

What is the most important information I should know about oseltamivir?

Oseltamivir is used to treat flu symptoms caused by influenza virus in patients who have had symptoms for less than 2 days. Oseltamivir may also be given to prevent influenza in people who may be exposed but do not yet have symptoms. Oseltamivir will not treat the common cold.

Before taking oseltamivir, tell your doctor if you have received a nasal flu vaccine within the past 2 weeks, or if you have kidney disease, heart disease, lung disease, or any other serious disease or health problem. Also tell your doctor if you have any condition causing swelling or disorder of the brain.

Treatment with oseltamivir should start as soon as possible when flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Take this medication for as many days as it has been prescribed for you even if you begin to feel better. Your symptoms may start to improve before the infection is completely treated. Some people using oseltamivir have had rare side effects of sudden confusion, delirium, hallucinations, unusual behavior, or self-injury. These symptoms have occurred most often in children. It is not known whether oseltamivir was the exact cause of these symptoms. However, anyone using oseltamivir should be watched closely for signs of confusion or unusual behavior. Call a doctor at once if you or the child using oseltamivir has any of these symptoms. Oseltamivir should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

It is dangerous to purchase oseltamivir on the Internet or from vendors outside of the United States. Samples of "Tamiflu" purchased on the Internet have been found to contain cloxacillin, a type of antibiotic that can have dangerous side effects in people who are allergic to penicillin.

What should I discuss with my healthcare provider before using oseltamivir?

Oseltamivir should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

You should not use this medication if you are allergic to oseltamivir.

Before taking oseltamivir, tell your doctor if you have used a nasal flu vaccine (FluMist) within the past 2 weeks, or if you have:

• kidney disease;

• heart disease;

• lung disease;

• a condition causing swelling or disorder of the brain; or

• any other serious disease or health problem.

FDA pregnancy category C. It is not known whether oseltamivir is harmful to an unborn baby. However, not receiving this medication to prevent influenza could be harmful to the baby if the mother becomes infected with a disease that oseltamivir could prevent. Before taking this medication, tell your doctor if you are pregnant. Your doctor will decide whether you should receive oseltamivir, especially if you have a high risk of infection with H1N1 influenza (also called "swine" flu). It is not known whether oseltamivir passes into breast milk or if it could harm a nursing baby. Do not take this medication without telling your doctor if you are breast-feeding a baby. Do not give this medication to a child younger than 1 year old.

How should I take oseltamivir?

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Treatment with oseltamivir should start as soon as possible when flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

Take the oseltamivir capsule with a full glass of water. Shake the oral suspension (liquid) well just before you measure a dose. To be sure you get the correct dose, measure the liquid with the syringe provided with the medicine. Do not measure the medicine with a regular table spoon. If you do not have the syringe or another medicine dose-measuring device, ask your pharmacist for one.

You may take oseltamivir with or without food. If the medicine upsets your stomach, it may help to take it with food or milk.

To treat flu symptoms: Take oseltamivir every 12 hours for 5 days.

To prevent flu symptoms: Take oseltamivir every 24 hours for 10 days or as prescribed. Follow your doctor's instructions.

Use this medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated. Tell your doctor if your symptoms do not improve, or if they get worse. Store oseltamivir capsules at room temperature away from moisture and heat. Store oseltamivir liquid in the refrigerator but do not freeze. Throw away any unused liquid after 10 days.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if your next dose is less than 2 hours away. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea and vomiting.

What should I avoid while taking oseltamivir?

Do not use a nasal flu vaccine (FluMist) within 48 hours after taking oseltamivir. Oseltamivir may interfere with the drug action of FluMist, making the vaccine less effective. Follow your doctor's instructions.

Oseltamivir side effects

Stop using oseltamivir and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat; a red and blistering or peeling skin rash. Some people using oseltamivir have had rare side effects of sudden confusion, delirium, hallucinations, unusual behavior, or self-injury. These symptoms have occurred most often in children. It is not known whether oseltamivir was the exact cause of these symptoms. However, anyone using oseltamivir should be watched closely for signs of confusion or unusual behavior. Call a doctor at once if you or the child using oseltamivir has any of these symptoms.

Less serious side effects may include:

• nausea, vomiting, diarrhea;

• dizziness, headache;

• nosebleed;

• eye redness or discomfort;

• sleep problems (insomnia); or

• cough or other respiratory symptoms.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: oseltamivir side effects (in more detail)

Oseltamivir Dosing Information

Usual Adult Dose for Influenza:

75 mg orally twice a day for 5 days

Severely ill hospitalized patients with 2009 H1N1 influenza virus infection (previously referred to as novel influenza A [H1N1] virus infection): Increasing the dose to 150 mg orally twice a day or extending the treatment duration can be considered.

Usual Adult Dose for Influenza Prophylaxis:

Following close contact with an infected individual: 75 mg orally once a day for at least 10 days; therapy should begin within 48 hours of exposure

During a community outbreak of influenza: 75 mg orally once a day

Safety and efficacy of oseltamivir prophylaxis have been established for up to 6 weeks in immunocompetent patients. Safety has been established for up to 12 weeks in immunocompromised patients. Protection lasts as long as dosing is continued.

Usual Adult Dose for Avian Influenza:

Postexposure prophylaxis: 75 mg orally once or twice a day for 7 to 10 days

Treatment:
Mild infection: 75 mg orally twice a day for 5 days
Severe infection: 150 mg twice a day for 7 to 10 days

Limited data are available.

Usual Pediatric Dose for Influenza:

The FDA has not approved dosing for patients less than 1 year of age. The following had been recommended for emergency use in full-term infants:
Weight-based dosing (preferred):
Less than 1 year: 3 mg/kg orally twice a day

Dosing by age (if weight not known):
Birth through 2 months: 12 mg orally twice a day
3 through 5 months: 20 mg orally twice a day
6 through 11 months: 25 mg orally twice a day

1 through 12 years:
15 kg or less: 30 mg orally twice a day
16 through 23 kg: 45 mg orally twice a day
24 through 40 kg: 60 mg orally twice a day
41 kg or greater: 75 mg orally twice a day

13 years or older: 75 mg orally twice a day

Duration: 5 days

Usual Pediatric Dose for Influenza Prophylaxis:

The FDA has not approved dosing for patients less than 1 year of age. The following had been recommended for emergency use in full-term infants:
Less than 3 months: Not recommended unless situation judged critical.

Weight-based dosing (preferred):
3 months to less than 1 year: 3 mg/kg orally once a day

Dosing by age (if weight not known):
3 through 5 months: 20 mg orally once a day
6 through 11 months: 25 mg orally once a day

1 through 12 years:
15 kg or less: 30 mg orally once a day
16 through 23 kg: 45 mg orally once a day
24 through 40 kg: 60 mg orally once a day
41 kg or greater: 75 mg orally once a day

13 years or older: 75 mg orally once a day

Prophylaxis after close contact with an infected individual is recommended for 10 days and should begin within 48 hours of exposure. Prophylaxis during a community outbreak of influenza may be continued for up to 6 weeks.

Usual Pediatric Dose for Avian Influenza:

Mild infection:
1 through 12 years:
15 kg or less: 30 mg orally twice a day
16 through 23 kg: 45 mg orally twice a day
24 through 40 kg: 60 mg orally twice a day
41 kg or greater: 75 mg orally twice a day

13 years or older: 75 mg orally twice a day

Limited data are available.

What other drugs will affect oseltamivir?

There may be other drugs that can interact with oseltamivir. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

Where can I get more information?

• Your pharmacist can provide more information about oseltamivir.