Class Name(s):

• 8:18.28 Neuraminidase Inhibitors

Pronunciation:

• (os el tam' I vir)

Brand Name(s):

• Tamiflu^®

WHY is this medicine prescribed?

Oseltamivir is used to treat some types of influenza infection ('flu') in adults, children, and infants (older than 2 weeks of age) who have had symptoms of the flu for no longer than 2 days. This medication is also used to prevent some types of flu in adults and children (older than 1 year of age) when they have spent time with someone who has the flu or when there is a flu outbreak. Oseltamivir is in a class of medications called neuraminidase inhibitors. It works by stopping the spread of the flu virus in the body. Oseltamivir helps shorten the time that flu symptoms such as a stuffy or runny nose, sore throat, cough, muscle or joint aches, tiredness, headache, fever, and chills last. Oseltamivir will not prevent bacterial infections, which may occur as a complication of the flu.

HOW should this medicine be used?

Oseltamivir comes as a capsule and a suspension (liquid) to take by mouth. When oseltamivir is used to treat flu symptoms, it is usually taken two times a day (morning and evening) for 5 days. When oseltamivir is used to prevent flu, it is usually taken once a day for at least 10 days, or for up to 6 weeks during a community flu outbreak. Oseltamivir may be taken with or without food, but is less likely to cause upset stomach if it is taken with food or milk. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part that you do not understand. Take oseltamivir exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

It is important to know the dose of medication your doctor has prescribed and to use a measuring device that will measure the dose accurately. If you are taking the medication yourself or giving it to a child older than 1 year of age, you can use the device provided by the manufacturer to measure the dose according to the instructions below. If you are giving the medication to a child under one year of age, you should not use the measuring device provided by the manufacturer because it cannot accurately measure small doses. Instead, use the device provided by your pharmacist. If the commercial suspension is unavailable and your pharmacist prepares a suspension for you, he or she will provide a device to measure your dose. Never use a household teaspoon to measure doses of oseltamivir oral suspension.

If you are giving the commercial suspension to an adult or child over one year of age, follow these steps to measure the dose using the syringe provided:

1. Shake the suspension well (for about 5 seconds) before each use to mix the medication evenly.
2. Open the bottle by pushing down on the cap and turning the cap at the same time.
3. Push the plunger of the measuring device completely down to the tip.
4. Insert the tip of the measuring device firmly into the opening on the top of the bottle.
5. Turn the bottle (with the measuring device attached) upside down.
6. Pull back on the plunger slowly until the amount of suspension prescribed by your doctor fills the measuring device to the appropriate marking. Some larger doses may need to be measured using the measuring device twice. If you are not sure how to correctly measure the dose your doctor has prescribed, ask your doctor or pharmacist.
7. Turn the bottle (with the measuring device attached) right-side up and slowly remove the measuring device.
8. Take oseltamivir directly into your mouth from the measuring device; do not mix with any other liquids.
9. Replace the cap on the bottle and close tightly.
10. Remove the plunger from the rest of the measuring device and rinse both parts under running tap water. Allow the parts to air dry before putting back together for the next use.

Call your doctor or pharmacist to find out how you should measure a dose of oseltamivir suspension if you do not have the measuring device that came with this medication.

If you have difficulty swallowing capsules, your doctor may tell you to open the capsule and mix the contents with a sweetened liquid. To prepare doses of oseltamivir for people who cannot swallow the capsules:

1. Hold the capsule over a small bowl and carefully pull open the capsule and empty all of the powder from the capsule into the bowl. If your doctor has instructed you to take more than one capsule for your dose, then open the correct number of capsules into the bowl.
2. Add a small amount of sweetened liquid, such as regular or sugar-free chocolate syrup, corn syrup, caramel topping, or light brown sugar dissolved in water to the powder.
3. Stir the mixture.
4. Swallow the entire contents of this mixture right away.

Continue to take oseltamivir until you finish the prescription, even if you start to feel better. Do not stop taking oseltamivir without talking to your doctor. If you stop taking oseltamivir too soon or skip doses, your infection may not be fully treated, or you may not be protected from the flu.

If you feel worse or develop new symptoms while taking oseltamivir, or if your flu symptoms do not start to get better, call your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.

Are there OTHER USES for this medication?

Oseltamivir may be used to treat and prevent infections from avian (bird) influenza (a virus that usually infects birds but can also cause serious illness in humans). Oseltamivir also may be used to treat and prevent infections from influenza A (H1N1).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before taking oseltamivir,

• tell your doctor and pharmacist if you are allergic to oseltamivir, any other medications, or any of the ingredients in oseltamivir capsules or suspension. Ask your pharmacist or check the manufacturer's patient information for a list of the ingredients.
• tell your doctor what prescription and nonprescription medications, vitamins, nutritional supplements and herbal products you are taking or plan to take while taking oseltamivir. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have ever taken oseltamivir to treat or prevent the flu.
• tell your doctor if you have any disease or condition that affects your immune system such as human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) or if you have heart, lung, or kidney disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking oseltamivir, call your doctor.
• you should know that people, especially children and teenagers, who have the flu may become confused, agitated, or anxious, and may behave strangely, have seizures or hallucinate (see things or hear voices that do not exist), or harm or kill themselves. You or your child may develop these symptoms whether or not you or your child uses oseltamivir, and the symptoms may begin shortly after starting treatment if you do use the medication. If your child has the flu, you should watch his or her behavior very carefully and call the doctor right away if he or she becomes confused or behaves abnormally. If you have the flu, you, your family, or your caregiver should call the doctor right away if you become confused, behave abnormally, or think about harming yourself. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.
• ask your doctor if you should receive a flu vaccination each year. Oseltamivir does not take the place of a yearly flu vaccine. If you received or plan to receive the intranasal flu vaccine (FluMist; flu vaccine that is sprayed into the nose), you should tell your doctor before taking oseltamivir. Oseltamivir may make the intranasal flu vaccine less effective if it is taken up to 2 weeks after or up to 48 hours before the intranasal flu vaccine is given.
• if you have fructose intolerance (an inherited condition in which the body lacks the protein needed to break down fructose, a fruit sugar, such as sorbitol), you should know that the oseltamivir suspension is sweetened with sorbitol. Tell your doctor if you have fructose intolerance.

What should I do IF I FORGET to take a dose?

If you forget to take a dose, take it as soon as you remember it. If it is no longer than 2 hours before your next scheduled dose, skip the missed dose and continue your regular dosing schedule. If you miss several doses, call your doctor for directions. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Oseltamivir may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea
• vomiting
• stomach pain
• diarrhea
• headache

Some side effects can be serious. If you experience any of these symptoms or those mentioned in the SPECIAL PRECAUTIONS section, call your doctor immediately:

• rash, hives, or blisters on the skin
• mouth sores
• itching
• swelling of the face or tongue
• difficulty breathing or swallowing
• hoarseness
• confusion
• speech problems
• shaky movements
• hallucinations (seeing things or hearing voices that do not exist)

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Symptoms of overdose may include:

• nausea
• vomiting

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in and out of reach of children. Store the capsules at room temperature and away from excess heat and moisture (not in the bathroom). Commercial oseltamivir suspension can be kept at room temperature for up to 10 days or in the refrigerator for up to 17 days. Oseltamivir suspension prepared by a pharmacist can be kept at room temperature for up to 5 days or in the refrigerator for up to 35 days. Do not freeze oseltamivir suspension.

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach. http://www.upandaway.org

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://goo.gl/c4Rm4p for more information.

What OTHER INFORMATION should I know?

Oseltamivir will not stop you from giving the flu to others. You should wash your hands frequently, and avoid practices such as sharing cups and utensils that can spread the virus to others.

Do not let anyone else take your medication. Your prescription is probably not refillable. If you still have symptoms of the flu after you finish taking oseltamivir, call your doctor.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: January 15, 2018.