Health Library

Oseltamivir (By mouth)

Oseltamivir (oh-sel-TAM-i-vir)

Treats and helps prevent influenza.

Brand Name(s):

Tamiflu

When This Medicine Should Not Be Used:

How to Use This Medicine:

Capsule, Liquid

• Your doctor will tell you how much medicine to use. Do not use more than directed. Do not take this medicine for any illness other than the flu.
• Start taking this medicine as soon as possible after flu symptoms begin or after you are exposed to the flu (within the first 2 days).
• Shake the oral liquid before each use. Measure the liquid medicine with the oral dispenser that came with the medicine. Ask your pharmacist for an oral measuring spoon or syringe if you do not have one.
• You may open the capsule and mix the contents with a sweet liquid (such as chocolate syrup, corn syrup, or sugar dissolved in water). Ask your doctor or pharmacist if you have any questions.
• Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.
• Missed dose: If you miss a dose and your next dose is due within 2 hours, skip the missed dose and take your medicine at the normal time. Do not use extra medicine to make up for a missed dose. If you miss a dose and your next dose is due in more than 2 hours, take the missed dose as soon as you can. Then take your next dose at the normal time, and go back to your regular schedule.
• Capsules: Store at room temperature, away from heat, moisture, and direct light.
• Oral liquid: Store in the refrigerator and use within 17 days. Do not freeze. You may also store the medicine at room temperature, but use it within 10 days. Throw away any medicine that has not been used within this time.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Do not use this medicine if you have received the live influenza vaccine (nasal mist) in the past 2 weeks or if you will receive the vaccine within 48 hours, unless your doctor says it is okay.

Warnings While Using This Medicine:

• Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, heart disease, lung disease, or a weakened immune system.
• This medicine may cause the following problems:
  • Serious skin reactions
  • Unusual thoughts or behaviors
• Call your doctor if your symptoms do not improve or if they get worse.
• The liquid form of this medicine contains sorbitol. Tell your doctor if you have hereditary fructose intolerance.
• This medicine is not a substitute for a yearly flu shot. It also will not prevent a bacterial infection.
• Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Blistering, peeling, red skin rash
• Confusion, agitation, seeing or hearing things that are not there, change in mood or behavior, seizures
• Fever, chills, cough, sore throat, body aches

If you notice these less serious side effects, talk with your doctor:

• Nausea, vomiting, diarrhea, stomach pain, or upset stomach

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 9/6/2024