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 influenza in people 2 weeks of age and older who have had flu symptoms for no more than 2 days. Oseltamivir may also be given to prevent influenza in people 1 year of age and older who may have been exposed but do not yet have symptoms. This medicine will not treat the common cold.

Oseltamivir will not treat or prevent illness caused by infections other than the influenza virus, and it does not prevent bacterial infections that may occur along with the flu. It has not been shown to be effective when treatment is started more than 2 days after flu symptoms begin. It is not known whether oseltamivir is effective for the treatment of the flu in people with long-term (chronic) heart or breathing problems, or for the treatment or prevention of the flu in people who have weakened immune systems (immunocompromised).

It is dangerous to purchase oseltamivir on the Internet or outside the United States. The sale and distribution of medicines outside the U.S. does not comply with safe-use regulations of the Food and Drug Administration (FDA). These medications 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.

Oseltamivir first received FDA approval on October 27, 1999, under the brand Tamiflu. Generic oseltamivir is available.

Take oseltamivir exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Start taking this medicine as soon as possible after flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose. For treatment, oseltamivir should be started within 2 days (48 hours) of the first appearance of flu symptoms.

Take the oseltamivir capsule with a full glass of water.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Oseltamivir may be taken with or without food; taking it with food may lessen stomach upset.

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.

If your healthcare provider or pharmacist has instructed you to open the capsules and mix the contents with a sweetened liquid (such as chocolate syrup, corn syrup, caramel topping, or light brown sugar dissolved in water), read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Tell your doctor if your symptoms do not improve, or if they get worse.

What happens if I miss a dose?

Use the medicine as soon as you can, but skip the missed dose if your next dose is due in less than 2 hours. Do not use two doses at one time.

What happens if I overdose?

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

What to avoid

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

Oseltamivir should not be used in place of getting a yearly flu shot. The Centers for Disease Control and Prevention (CDC) recommends an annual flu shot to help protect you each year from new strains of influenza virus. You can get a flu shot even while using this medicine.

You should not use oseltamivir if you are allergic to it.

Do not use oseltamivir to prevent influenza in a child younger than 1 year old. Do not use this medicine to treat influenza in a child younger than 2 weeks old unless instructed by your doctor.

Tell your doctor if you have ever had:

• kidney disease (or if you are on dialysis). Oseltamivir is not recommended for people with end-stage renal disease (ESRD) who are not receiving dialysis;
• heart disease or chronic lung disease;
• a condition causing swelling or disorder of the brain;
• a weak immune system (caused by disease or by using certain medicine);
• a history of hereditary fructose intolerance. Oseltamivir oral suspension contains sorbitol and may cause stomach upset and diarrhea in people who are fructose intolerant; or
• if you have used a nasal flu vaccine (FluMist) within the past 2 weeks.

Available information indicates that oseltamivir does not increase the risk of birth defects. Getting sick with influenza during pregnancy can cause complications leading to birth defects, low birth weight, preterm delivery, or stillbirth. Your doctor will decide whether you should receive oseltamivir if you are pregnant.

The Centers for Disease Control and Prevention (CDC) recommends that pregnant women may receive a yearly flu vaccine to prevent influenza. Oseltamivir is not to be used in place of the yearly flu shot.

Oseltamivir can pass into breast milk in small amounts. Tell your doctor if you are breastfeeding a baby.

Serious side effects

Oseltamivir may cause serious side effects, including:

• Serious skin and allergic reactions. Oseltamivir can cause serious skin and allergic reactions. Stop taking oseltamivir and get medical help right away if you get any of the following symptoms: skin rash or hives your skin blisters and peels swelling of your face, eyes, lips, tongue, or throat trouble breathing blisters or sores in your mouth chest pain or tightness itching
• Change in behavior. People, especially children, who have the flu can develop nervous system problems and abnormal behavior that can lead to death. During treatment with oseltamivir, tell your healthcare provider right away if you or your child have confusion, speech problems, shaky movements, seizures, or start hearing voices or seeing things that are not really there (hallucinations).

Common side effects

The most common side effects of oseltamivir when used for treatment of the flu include nausea, vomiting, and headache.

The most common side effects of oseltamivir when used for prevention of the flu include nausea, vomiting, headache, and pain.

Tell your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all of the possible side effects of oseltamivir. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Other drugs may interact with oseltamivir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Avoid the nasal spray flu vaccine (FluMist) in the 2 weeks before or the 48 hours after taking Tamiflu, since the medicine can make this vaccine work less well. Your doctor may make an exception if needed.

Store oseltamivir capsules at room temperature away from moisture and heat.

Store the liquid medicine in the refrigerator (36°F to 46°F / 2°C to 8°C) but do not freeze. Throw away any unused liquid after 17 days. The liquid may also be stored at cool room temperature (68°F to 77°F / 20°C to 25°C) for up to 10 days.

Active ingredient: oseltamivir phosphate

Inactive ingredients (Tamiflu):

• Tamiflu capsules: croscarmellose sodium, povidone K30, pregelatinized starch, sodium stearyl fumarate, and talc 30 mg capsule shell: gelatin, red iron oxide, titanium dioxide, and yellow iron oxide 45 mg capsules shell: black iron oxide, gelatin, and titanium dioxide 75 mg capsules shell: black iron oxide, gelatin, red iron oxide, titanium dioxide, and yellow iron oxide
• Tamiflu for oral suspension: monosodium citrate, saccharin sodium, sodium benzoate, sorbitol, titanium dioxide, tutti-frutti flavoring, and xanthan gum.

Tamiflu is available as oral capsules (30 mg, 45 mg, 75 mg) and a powder for oral suspension (360 mg oseltamivir base supplied as powder and constituted to a final concentration of 6 mg/mL).

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