Oseltamivir (Oral)

Oseltamivir is used in the treatment and prevention of infections caused by the influenza A and B flu viruses and swine influenza A.


This medicine is indicated for use in adults and children, including infants who are 2 weeks of age and older. It should be used only for flu symptoms that have started no more than 48 hours before treatment.

Flu symptoms include sore throat, stuffy or runny nose, headache, cough, fever, chills, muscle or joint aches, and tiredness.

Adults, and children 1 year of age and older, are also treated with Oseltamivir to prevent certain types of flu when these patients were exposed to someone with the flu or a flu outbreak.

Oseltamivir is an antiviral that falls into a class of medicines known as neuraminidase inhibitors. It effectively stops the flu virus from spreading in the body. This helps to shorten the length of time the flu symptoms last.

Patients begin to feel better usually within 2 to 3 days.

The US Food and Drug Administration (FDA) cautions patients to continue taking their yearly flu vaccination since Oseltamivir is not a substitute for the flu shot.

The medicine is not for treating or preventing infections caused by bacteria, even if these infections occur at the same time with the flu.

Oseltamivir is the generic name for the US brand of the drug called Tamiflu. It is given to patients by doctor's prescription only.

Conditions Treated

  • Symptoms of Influenza A and B
  • Swine Influenza A

Type Of Medicine

  • Antiviral

Side Effects

Prescription medicines, such as Oseltamivir, generally cause various side effects. Some of them are necessary and expected as the medicine works in the body.

Some patients may experience one or more side effects, but all of them may not be experienced by one single patient.

Some side effects are unwanted and may or may not require medical attention.

Call your doctor right away if you experience any of the side effects on the followings lists.

Less commonly occur

  • Wheezing
  • Cough that brings up phlegm

Rarely occur

  • Shortness of breath
  • Fast or irregular heartbeat
  • Swelling of the face
  • Pain
  • Drooling
  • Tenderness or cramps in the stomach or abdomen
  • Pain in the jaw, back or arm
  • Bloating
  • Hoarseness
  • Pain or discomfort in the chest
  • Weight loss that cannot be explained
  • Diarrhea (may be watery and severe, and bloody)
  • Increase in thirst

There are side effects that may occur but the frequency or severity with which they do are unknown. Some of them are as follows:

Incidence unknown

  • Hives or welts
  • Fainting
  • Eyes that look red or irritated
  • Convulsions (seizures)
  • Unable to control the bladder
  • Dark urine
  • Difficulty swallowing
  • Heartbeat that is slow, fast or irregular
  • Skin and eyes that appear yellow
  • Puffiness, itching or swelling of the lips, tongue, face, eyelids or area around the eyes
  • Sweating
  • Light-colored stools
  • Itching or skin rash about the entire body
  • Loss of consciousness
  • Skin lesions that are red (may have a purple-colored center)
  • Extreme jerkiness or muscle spasm
  • Pain in the joint or muscle
  • Pain in the stomach or the upper right abdomen
  • Blistering, peeling or loosening of the skin
  • White spots, ulcers or sores on the lips or in the mouth

Some side effects may occur that are not considered as 'œserious,' and generally do not need medical attention. They can be managed by the patient and may go away on their own during treatment.

The following are examples of such side effects. If any of them occurs but gets worse, bothersome or does not go away tell your doctor.

More commonly occur

  • Vomiting
  • Diarrhea
  • Nausea

Less commonly occur

  • Dizziness
  • Trouble sleeping
  • Itching, burning or dry eyes (mainly occurs in children)
  • Pain in the stomach or abdomen
  • Excessive tearing of the eyes (mainly occurs in children)
  • Pain, redness, swelling of the eye or eyelid (mainly occurs in children)
  • Bloody nose or unexplained nosebleeds (mainly occurs in children)
  • Ear disorder (occurs mainly in children)

Rarely occurs

  • Unusual bleeding or bruising
  • Troubled breathing
  • Pale skin

Incidence not known

  • Dryness of the mouth
  • Blurred vision
  • Flushed, dry skin
  • Mental or mood changes
  • Dry, cracked, or scaly skin
  • Rash on the skin that is scaly, crusty and oozing

Some patients may experience other side effects not mentioned in this guide. If you experience any unusual symptom that bothers you or does not go away, tell your doctor.

Your doctor or healthcare professional may give you information on how to prevent or reduce side effects.

You may also call the FDA at 1-800-FDA-1088 to report side effects.


Oseltamivir (Tamiflu) is supplied as a capsule or powder to be mixed into a liquid suspension. The capsule or liquid is taken by mouth. Treatment should be started within 48 hours of having the flu symptoms, but no later.

The oral suspension is the preferred treatment for patients who are unable to swallow capsules. The pharmacist usually prepares the suspension by mixing the powder with water, before giving it to you.

Dosage usually varies from one patient to the other. Your dosage information will be on the prescription label. It will be based on the condition you are being treated for and whether it is for existing flu symptoms or prevention of a flu infection.

Dosage, especially for children and infants, is strictly based on age and exact weight.

The prescription label should tell you the strength of your dose, how often you should take it, the time between each dose, and the duration of your treatment.

Follow this and all other directions given to you by your doctor or pharmacist, and the prescription label. If you are still not sure how to take your medicine, ask your doctor or pharmacist to explain.

Treatment of flu symptoms using oral capsules or suspension:

Adults and teenagers:

Take 75 milligrams (mg) or 12.5 milliliters (mL) twice a day. Take the first dose in the morning and the second dose in the evening. Do this for 5 days.

Children (aged 1 year or older): The dose will be determined by your child's doctor based on your child's body weight. A dose of between 30 to 75 mg or 5 to 12.5 mL taken 2 times a day for 5 days is usually prescribed.

Children (2 weeks old to less than 1 year of age): The dose will be determined by your child's doctor based on your child's body weight. A dose of between 3 mg per kg of body weight two times a day for 5 days is usually given.

Children (2 weeks of age or younger): Oseltamivir is not recommended for treating this group of children.

Prevention of the flu using oral capsules or suspension:

Adults and teenagers:

Take 75 milligrams (mg) or 12.5 milliliters (mL) 1 time per day, every day, for at least 10 days.

Children (aged 1 year or older): The dose will be determined by your child's doctor based on your child's body weight. A dose of between 30 to 75 mg or 5 to 12.5 mL taken 1 time a day for 10 days is usually prescribed.

Children (less than 1 year of age): Oseltamivir is not recommended for treating this group of children.

Your pharmacist should give you a dispenser to measure the medicine for you or your child. If you have not received one, ask your pharmacist to provide it.

You may mix your child's medicine with small amounts of applesauce or chocolate syrup to give it a taste your child may prefer.

If you find it difficult to swallow the capsule, you may be directed by your doctor to take it using the following instructions:

Mixing the contents of the capsule:

1. Carefully pull open the capsule while holding it over a small bowl or cup.

2. Empty all of the powder from the capsule into the container. If your doctor told you to take more than 1 capsules for each dose, open each capsule and pour the powder into the cup/bowl.

3. Add a small amount of sweetened liquid to the powder and stir. You may use light brown sugar dissolved in a small amount of water or sugar-free or regular chocolate syrup as your sweetened liquid.

4. Swallow all of the mixture immediately.

Missed Dose

If you missed a dose of the oral capsule or suspension, take it as soon as possible. However, if it is less than 2 hours before your next scheduled dose, skip the missed dose and take the next dose at the regular time.

An extra dose should not be taken to make up for the missed dose.


Call your doctor, 911 and/or the local poison control center at 1-800-222-1222 if you overdose on this drug. Symptoms of overdose are as follows:

  • Nausea
  • Vomiting

If the patient collapses or is not breathing, call 911.


Other medicines or medical problems that increase the risk of side effects or decrease the effectiveness of Oseltamivir should be avoided during treatment. Oseltamivir may also block the effects of other drugs being used by the patient.

Food, alcohol, and tobacco

This medicine may be taken with or without food. However, food may affect the medicine. Your doctor may tell you whether you should or should not eat food around the time of taking your doses.

You may also be given special instructions on the use of alcohol or tobacco.

Other medicines

There is a potential for an increase in the risk of certain side effects if any of the following medicines is used with Oseltamivir. However, using them together may be best for your health.

The following interactions are mentioned in this guide because of their potential significance.

It is not usually recommended to use the following medication with Oseltamivir. If its use cannot be avoided, your doctor may change your dose or how often you use any of your medicines.

  • Warfarin

Other interaction not listed here may also occur. You may ask your doctor for more information about drug interaction.

Other medical problems

Since the presence of other medical problems in patients taking this flu medicine may affect the way the medicine works, you should tell your doctor about any other medical problem you have.

The safety of this medication is not established for use in patients with the following conditions:

  • Liver disease (severe)
  • Heart disease
  • Serious medical problems that may require hospitalization
  • Weakened immune system
  • Illnesses caused by viruses other than influenza Type A or B
  • Lung disease

The oral suspension contains sorbitol which may cause the following condition to become worse. Therefore, use it with caution.

  • Hereditary Fructose Intolerance (HFI)

Use Oseltamivir with caution in patients who have the following condition. This is necessary due to the slow removal of the medicine from their body.

  • Kidney disease


  • Do not use Oseltamivir if you are allergic to it or any of its ingredients.
  • Do not use this flu medicine if you are allergic to other medicines.
  • Tell your doctor if you are allergic to certain foods, dyes, preservatives, or animals.
  • Children 12 years of age and under should not use this medicine unless it was prescribed by a doctor for the treatment or prevention of flu.
  • Do not treat children under 2 weeks of age for symptoms of influenza with this medicine. Do not give it to children under 1 year of age to prevent influenza. Safety and efficacy for these age groups have not been established.
  • Tell your doctor if you are pregnant, may become pregnant or are breastfeeding. There may be a potential risk of harm to an unborn child or a breastfeeding infant.

Your doctor will consider the potential benefits and risks when deciding to treat you.

  • Do not use other medicines while taking Oseltamivir unless your doctor approves.
  • Let your doctor know about all prescription or non-prescription medicines or vitamins or herbal products you take or plan to take.
  • To avoid adverse interaction during treatment with Oseltamivir, tell your doctor about any other medical problem you have or have a history of. This will help your doctor take necessary precautions when treating you.
  • Take your dose exactly as prescribed. Give your child the correct dose of the medicine, as directed by your child's doctor or pharmacist. Measure the medicine correctly using the dispenser provided.
  • Do not stop taking this medicine until you have taken it for the full prescribed time, even if you start to feel better. Stopping sooner than you were directed to may cause the virus to continue spreading or reduce the effectiveness of the medicine.
  • Tell your doctor if your flu symptoms become worse, do not go away or if you notice new symptoms.
  • Oseltamivir is not a flu vaccine. You (and your child) should continue to take your yearly flu vaccination.
  • Tell your doctor if you have heart, kidney or lung disease. Also let your doctor know if you have any condition or disease that affects your immune system, such as human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS).
  • If you took or plan to take intranasal flu vaccine (vaccine sprayed into the nostril), you should tell your doctor before using Oseltamivir.

Oseltamivir may reduce the effectiveness of this vaccine if it is taken up to 2 weeks after or up to 48 hours before the intranasal flu vaccine is taken.

  • Do not take the capsule by breaking or chewing it before swallowing. Swallow it whole with a glass of water.

If you cannot swallow the capsule, ask your doctor to explain how to open the capsule and prepare an oral liquid using the powder it contains.


Store the capsules at room temperature. You may store the oral suspension at room temperature for up to 10 days. The oral liquid may be kept in the refrigerator but must be used within 17 days after it was mixed.

Keep the medicine away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Throw away medicine that is expired or no longer needed.

You may ask your healthcare professional or local waste disposal agency how to safely dispose of the capsules or suspension.


Oseltamivir effectively treats and prevents infections caused by the influenza A and B flu viruses and swine influenza A. It can be easily taken by mouth as a capsule or an oral liquid suspension.

It is used to treat children and adults. The approval of this medicine is significant in the treatment and prevention of these types of flu, particularly in children.

This is because children fall into what the US Food and Drug Administration (FDA) regards as a 'œvulnerable population.'

In fact, Oseltamivir is the only approved drug for treating infants younger than age 1 who have an influenza infection. This group of children is most likely to develop complications from the flu.

Children as young as 2 weeks of age who have flu symptoms can be safely treated with Oseltamivir. Children under the age of 6 months have the highest rate of hospitalization due to flu, says the Center for Disease Control and Prevention (CDC).

To clear up the flu virus infection completely, patients are required to take the full treatment of the medicine (usually 5 days), even if they feel better before the end of the treatment.

Patients must remember that Oseltamivir is for treating certain types of flu. It cannot treat bacterial infections. It is also not a substitute for the flu shot and will not protect patients from other strains of flu viruses.