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Generic name: tecovirimat
Dosage form: capsules and injection
Drug class: Miscellaneous antivirals

Medically reviewed by Judith Stewart, BPharm. Last updated on Aug 23, 2023.

What is TPOXX?

TPOXX is a prescription medicine used to treat smallpox disease caused by a type of virus called variola virus in adults and children who weigh at least 7 pounds (3 kg).

The effectiveness of TPOXX has been studied only in animals with orthopoxvirus diseases. There have been no human studies in people who have smallpox disease.

The safety of TPOXX was studied in adults. There have been no studies in children 17 years of age and younger.

TPOXX may not work well in people who have a weakened immune system (immunocompromised).

TPOXX works as an antiviral by inhibiting the orthopoxvirus VP37 envelope wrapping protein.

What is TPOXX used for?


TPOXX is a FDA approved medicine used to treat smallpox, a contagious, disfiguring and often deadly disease caused by the variola virus. 

Naturally occurring smallpox was eradicated worldwide by 1980 through a global immunization campaign.

Samples of smallpox virus have been kept in laboratories for research purposes, leading to concerns of potential use as a biological warfare agent.


TPOXX is also used under a CDC Investigational New Drug protocol to treat monkeypox in people with severe disease, or who are more likely to get severely ill, such as people with weakened immune systems. 

There have been no human studies in people who have monkeypox disease.

Who should not receive TPOXX injection?

Do not receive TPOXX injection if you or your child have severe kidney problems.

TPOXX injection contains an ingredient called hydroxypropyl β-cyclodextrin which is cleared from your body through the kidneys. Tell your healthcare provider if you or your child have kidney problems because receiving TPOXX injection may not be right for you or your child.

Before taking or receiving TPOXX

Before taking or receiving TPOXX, tell your healthcare provider about all of your or your child’s medical conditions, including if you or your child:

What other drugs will affect TPOXX?

Tell your healthcare provider about all of the medicines you or your child take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Using TPOXX with certain other medicines may affect each other causing possible serious side effects.

You can ask your healthcare provider or pharmacist for a list of medications that interact with TPOXX.

Especially tell your healthcare provider if you take a medicine used to treat type 2 diabetes called repaglinide.

Know the medicines you or your child take. Keep a list of your medicines to show your healthcare provider and pharmacist when you get a new medicine.

Do not start taking a new medicine without telling your healthcare provider. Your healthcare provider can tell you if it is safe to take TPOXX with other medicines.

How should I take TPOXX?

TPOXX capsules:

TPOXX Injection for Intravenous Infusion (IV):

TPOXX injection is given to you or your child by intravenous (IV) infusion into a vein slowly over 6 hours using an infusion pump by a health care provider.

Dosing information

Usual Pediatric and Adult Dosage for Smallpox

Pediatric and Adult Patients weighing 40 kg or more (Oral Dosing):

Pediatric and Adult Patients weighing 13 kg or more and those who cannot swallow capsules (Oral Dosing):

TPOXX Capsules can be administered by carefully opening the number of capsule noted below and mixing and administering the entire contents in 30 mL of liquid (e.g., milk, chocolate milk) or soft food (e.g., apple sauce, yogurt):

Pediatric and Adult Patients weighing 3 kg and above (2.5) (Intravenous Dosing):

- Pediatric patients weighing 13 kg or more should be switched to TPOXX Capsules to complete the 14-day treatment course as soon as oral therapy can be tolerated.

Use: treatment of human smallpox disease in adults and pediatric patients weighing at least 3 kg.

TPOXX side effects

TPOXX may cause serious side effects, including:

The most common side effects of TPOXX capsules include:

The most common side effects of TPOXX injection include:

These are not all the possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store TPOXX capsules?

General information about the safe and effective use of TPOXX.

Medicines are sometimes prescribed for purposes other than those listed in a Patient Information leaflet. Do not use this medicine for a condition for which it was not prescribed. Do not give it to other people, even if they have the same symptoms that you have. It may harm them. You can ask your pharmacist or healthcare provider for information that is written for health professionals.

What are the ingredients in TPOXX?

TPOXX capsules: 200 mg:

Active ingredient: tecovirimat
Inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, hydroxypropyl methyl cellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and sodium lauryl sulfate.
The capsule shell is made of gelatin, FD&C blue No.1, FD&C red No.3, FD&C yellow No.6, and titanium dioxide.

TPOXX injection: 200 mg in each 20 mL vial

Active ingredient: tecovirimat
Inactive ingredients: hydroxypropyl β-cyclodextrin and water for injection.

Frequently asked questions

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.