Generic name: oseltamivir (oh-sel-TAM-i-vir FOS-fate)
Drug class: Neuraminidase inhibitors
Medically reviewed by Drugs.com. Last updated on Dec 31, 2021.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
- Powder for Suspension
Therapeutic Class: Antiviral
Pharmacologic Class: Oseltamivir
Uses for oseltamivir
Oseltamivir belongs to the family of medicines called antivirals, which are used to treat infections caused by viruses. Oseltamivir is used in the treatment of the infection caused by the flu virus (influenza A and influenza B). Oseltamivir may also be used to prevent and treat swine influenza A.
Oseltamivir may reduce flu symptoms (weakness, headache, fever, cough, runny or stuffy nose, and sore throat) by 1 day. Oseltamivir is also used to prevent influenza infection if you have come into close contact with someone who has the flu.
If you receive the flu vaccine every year, continue to do so. Oseltamivir is not a substitute for your yearly flu shot.
Oseltamivir is available only with your doctor's prescription.
Before using oseltamivir
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For oseltamivir, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to oseltamivir or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Oseltamivir is not indicated to treat flu in children younger than 2 weeks of age nor to prevent flu in children younger than 1 year of age. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of oseltamivir in the elderly.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking oseltamivir, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using oseltamivir with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of oseltamivir. Make sure you tell your doctor if you have any other medical problems, especially:
- Heart disease or
- Illnesses caused by viruses other than influenza Type A or B or
- Liver disease, severe or
- Lung disease or
- Serious medical problems that may need admission to a hospital or
- Weakened immune system—Safety of oseltamivir for people with these conditions is not established.
- Hereditary fructose intolerance—Use with caution. The oral suspension contains sorbitol, which can make this condition worse.
- Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
Proper use of oseltamivir
Talk to your doctor about the possibility of getting a flu shot if you or your child have not had one yet. Oseltamivir comes with a patient information leaflet. Read this information carefully and talk to your doctor if you have any questions.
For patients taking oseltamivir for the treatment of flu: Oseltamivir works best if taken within 2 days of having flu symptoms (e.g., weakness, headache, fever, cough, runny or stuffy nose, and sore throat). Oseltamivir should be taken for 5 days. Continue taking oseltamivir for the full time of treatment even if you begin to feel better after a few days. This will help clear up your infection completely. If you stop taking oseltamivir too soon, your symptoms may return.
For patients taking oseltamivir for the prevention of flu after an exposure: The medicine should be taken within 2 days of being exposed to the flu. Oseltamivir should be taken for at least 10 days.
You may take oseltamivir with meals or on an empty stomach. Taking oseltamivir with food may lessen the possibility of stomach upset.
The oral liquid form of oseltamivir is available in two dosage strengths (concentrations). Check with your doctor if you have any questions about the dosing instructions, how to measure a dose using the new dosing dispenser (in mL), or about which concentration of Tamiflu® for oral suspension you have.
For patients taking the oral liquid:
- Oseltamivir is to be taken only by mouth. Shake it well before using. Use the specially marked dosing dispenser that comes with the medicine to measure each dose accurately. The average household teaspoon may not hold the right amount of liquid. If the measuring device is lost or damaged, contact your pharmacist or doctor to find out the appropriate dose.
- Do not use the medicine after the expiration date on the label. The medicine may not work properly after that date. If you have any questions about this, check with your pharmacist.
If the oral liquid is not available, you may open the capsules and mix the contents in a bowl with sweetened liquids such as regular or sugar-free chocolate syrup, corn syrup, caramel topping, or light brown sugar (dissolved in water). Ask your doctor or pharmacist if you have any questions.
The dose of oseltamivir will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of oseltamivir. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage forms (capsules or suspension):
- For treatment of the flu:
- Adults and teenagers—75 milligrams (mg) or 12.5 milliliters (mL) two times a day (one in the morning and one in the evening) for 5 days.
- Children 1 year of age and older—Dose is based on body weight and must be determined by your doctor. It is usually between 30 to 75 mg or 5 to 12.5 mL two times a day for 5 days.
- Children 2 weeks of age to less than 1 year of age—Dose is based on body weight and must be determined by your doctor. It is usually 3 mg per kg of body weight two times a day for 5 days.
- Children younger than 2 weeks of age—Use is not recommended.
- For prevention of the flu:
- Adults and teenagers—75 milligrams (mg) or 12.5 milliliters (mL) once a day for at least 10 days.
- Children 1 year of age or older—Dose is based on body weight and must be determined by your doctor. It is usually between 30 to 75 mg or 5 to 12.5 mL once a day for 10 days.
- Children younger than 1 year of age—Use is not recommended.
- For treatment of the flu:
If you miss a dose of oseltamivir, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
If you miss a dose or forget to use it, take it as soon as you can, except if it is less than 2 hours before your next dose. Take your next dose at the normal time. Do not use extra medicine to make up for a missed dose.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Store the capsules at room temperature, away from heat, moisture, and direct light.
Store the oral liquid in the refrigerator and use it within 17 days after it has been mixed. Do not freeze. You may also store it at room temperature for up to 10 days. Throw away any mixed medicine that has not been used within this time.
Precautions while using oseltamivir
It is very important that your doctor check your or your child's progress after treatment. This is to make sure that the infection is cleared up completely, and to allow your doctor to check for any unwanted effects.
Oseltamivir is not a substitute for an annual flu shot. It also will not keep you or your child from getting a bacterial infection that starts with flu-like symptoms.
Oseltamivir may cause a serious type of allergic reaction called anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you or your child are using oseltamivir.
Serious skin reactions can occur with oseltamivir. Stop using oseltamivir and check with your doctor right away if you have blistering, peeling, or loosening of the skin, red skin lesions, severe acne or skin rash, sores or ulcers on the skin, or fever or chills while you or your child are using oseltamivir.
Oseltamivir may cause some people, especially children and teenagers, to be agitated, irritable, or display other abnormal behaviors, which may result in injury. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.
Make sure your doctor knows if you or your child plan to get the live nasal mist flu vaccine before you start using oseltamivir. You should not receive the vaccine within 2 weeks before or 48 hours after using oseltamivir.
If your or your child's symptoms do not improve after you or your child finish taking the medicine, or if they become worse, check with your doctor.
Oseltamivir side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- Phlegm-producing cough
- Abdominal or stomach cramps or tenderness
- arm, back, or jaw pain
- chest pain or discomfort
- diarrhea, watery and severe, which may also be bloody
- facial swelling
- fast or irregular heartbeat
- increased thirst
- shortness of breath
- unusual weight loss
Incidence not known
- Blistering, peeling, or loosening of the skin
- convulsions (seizures)
- dark urine
- difficulty with swallowing
- fast, slow, or irregular heartbeat
- hives or welts
- itching, puffiness, or swelling of the eyelids or around the eyes, face, lips, or tongue
- joint or muscle pain
- light-colored stools
- loss of bladder control
- loss of consciousness
- muscle spasm or jerking of all extremities
- red skin lesions, often with a purple center
- red, irritated eyes
- skin rash or itching over the entire body
- sores, ulcers, or white spots in the mouth or on the lips
- upper right abdominal or stomach pain
- yellow eyes and skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Abdominal or stomach pain
- bloody nose or unexplained nosebleeds (occurs mainly in children)
- burning, dry, or itching eyes (mainly in children)
- ear disorder (occurs mainly in children)
- excessive tearing of the eyes (mainly in children)
- redness, pain, or swelling of the eye or eyelid (mainly in children)
- trouble with sleeping
- Pale skin
- troubled breathing
- unusual bleeding or bruising
Incidence not known
- blurred vision
- cracked, dry, or scaly skin
- dry mouth
- flushed, dry skin
- mood or mental changes
- skin rash that is encrusted, scaly, and oozing
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Frequently asked questions
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