Tamiflu

Introduction

Written by Sarah Lewis, PharmD
Medically reviewed by Alex Brewer, PharmD, MBA
Updated on July 27, 2023

Oseltamivir (oh sel TAM i vir) is a generic medication prescribed to treat or help prevent the flu in adults and certain children. Oseltamivir belongs to a group of drugs called neuraminidase inhibitors.

Side effects of oseltamivir

Oseltamivir may cause mild or serious side effects. More common mild side effects of oseltamivir and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about oseltamivir’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for oseltamivir listed in the “Resources” section.

Mild side effects

More common mild side effects reported with some forms of oseltamivir are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about oseltamivir’s side effects, refer to the prescribing information for oseltamivir listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Mild side effects of oseltamivir oral capsule and oral liquid suspension* include:

• headache
• nausea
• pain
• vomiting
• mild allergic reaction†

* A suspension is a type of liquid mixture.
† For details about this side effect, see the “Interactions and warnings for oseltamivir” section.

Serious side effects

Serious side effects of oseltamivir are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about oseltamivir’s side effects, refer to the prescribing information for oseltamivir listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, oseltamivir’s serious side effects include:

• behavioral changes, including confusion or unusual behavior, especially in children
• severe allergic reaction*

* For details about this side effect, see the “Interactions and warnings for oseltamivir” section.

Common questions about oseltamivir

Below you’ll find answers to a few commonly asked questions about oseltamivir.

What brand names are available for oseltamivir?

Oseltamivir is available as the brand-name medication, Tamiflu. Oseltamivir is a generic drug.

A generic medication is an identical copy of the active drug in a brand-name medication. (An active drug is the ingredient that makes a medication work.) Generic drugs are believed to be as effective and safe as brand-name drugs. And generic drugs typically cost less than brand-name drugs.

To learn more about Tamiflu, talk with your doctor or pharmacist.

Is oseltamivir available over the counter?

No, oseltamivir isn’t available over the counter (OTC). You’ll need a prescription from your doctor to get it.

To relieve symptoms of the flu, there are OTC medications that can help. Talk with your doctor or pharmacist if you think you have the flu. They can give you more information about flu remedies.

Can oseltamivir be used for COVID-19?

Possibly. Oseltamivir isn’t approved for COVID-19 infection. But doctors may choose to prescribe it for this purpose. With off-label use, doctors prescribe a medication for purposes other than its approved uses.

To learn more about taking oseltamivir for COVID-19, talk with your doctor.

How does oseltamivir work? And how long does it take to start working?

Oseltamivir works by blocking an enzyme (a type of protein) that the flu virus needs to reproduce. This stops the virus from multiplying (making more virus) and spreading in your body.

Oseltamivir will start working as soon as you take it. But it can take a few days for your symptoms to ease. To get the full benefit, it’s important to finish the entire prescription according to your doctor’s instructions. This is even if your symptoms start easing.

If you’d like to know more about this, talk with your doctor or pharmacist.

Uses of oseltamivir

The Food and Drug Administration (FDA) approves prescription drugs such as oseltamivir for certain conditions. Approved uses for oseltamivir are described below.

Use for flu

Doctors may prescribe oseltamivir oral capsule or oral liquid suspension* to treat or help prevent influenza infection (commonly called the flu). To treat the flu, it’s used in adults and children ages 2 weeks and older who’ve had flu symptoms for 48 hours or less. To help prevent the flu, it’s used in adults and children ages 1 year and older. Oseltamivir is usually prescribed as a short-term treatment.

With the flu, you contract the influenza virus and usually have symptoms for about a week. Symptoms can include fever, chills, body aches, cough, fatigue (low energy), and headache. Taking oseltamivir can lower the severity of flu symptoms or shorten their length by 1–2 days. It can also help prevent the flu if you’ve been around someone who has it.

Doctors may not prescribe oseltamivir oral capsule or oral liquid suspension in certain situations. This includes if you have severe kidney disease without having dialysis.

* A suspension is a type of liquid mixture.

Interactions and warnings for oseltamivir

Below, you’ll find information about oseltamivir’s possible interactions and warnings.

Interactions of oseltamivir

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take oseltamivir, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription or over-the-counter drugs
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for oseltamivir” section below.

Warnings for oseltamivir

Some people should not take oseltamivir and others should take it cautiously.

Oseltamivir could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether oseltamivir is a safe option for you.

Ask your doctor about specific warnings for oseltamivir, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Oseltamivir can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to oseltamivir or any of its ingredients, your doctor will likely not prescribe oseltamivir. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• severe skin rashes that may blister and peel
• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to oseltamivir, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of oseltamivir

If you take oseltamivir by mouth, you should not take more than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken too much oseltamivir, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and oseltamivir

Information about oseltamivir and pregnancy and breastfeeding is described below.

Oseltamivir and pregnancy

It’s not known whether oseltamivir should be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication.

Oseltamivir and breastfeeding

It’s not known whether oseltamivir should be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication.

What to ask your doctor

Let your doctor know whether you have questions about oseltamivir or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• How should I take oseltamivir?
• Do I have a higher risk of side effects than others?
• Should I get a flu shot?

Resources

• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Oseltamivir phosphate capsules, for oral use. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/82fc6ef1-cc49-4f65-a91d-04a8572689cb/spl-doc
• Oseltamivir phosphate for oral suspension. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/c6f78d2d-6452-4af3-83c6-b044d1604bdc/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.