Tpoxx (Tecovirimat) - Oral

What Is Tpoxx?

Tpoxx (tecovirimat) is a medication treatment option for smallpox in people weighing a minimum of 3 kilograms (6.6 pounds).

Tpoxx is an antiviral medication. It works by blocking the activity of the VP37 viral protein. Inhibiting this protein prevents the virus from becoming a mature and enveloped (enclosed) virus. Blocking this protein also interferes with the virus's ability to get out of infected cells and spread to other cells.

Tpoxx is available as a prescription capsule. It's also available as a solution mixed with certain fluids for an intravenous infusion.

Drug Facts

Generic Name: Tecovirimat

Brand Name(s): Tpoxx

Drug Availability: Prescription

Therapeutic Classification: Antiviral medication

Available Generically: No

Controlled Substance: No

Administration Route: Tpoxx is available as oral capsules or an intravenous solution used for infusion.

Active Ingredient: Tecovirimat

Dosage Form(s): Tpoxx is available as oral capsules or an intravenous solution used for infusion.

What Is Tpoxx Used For?

Tpoxx is an oral or intravenous medication used for smallpox.

Smallpox was a serious infectious disease. From the World Health Organization's (WHO) efforts beginning in 1967, many people worldwide became vaccinated against smallpox. For this reason, WHO recommended stopping these vaccinations in 1979—with certain exceptions, such as for people researching smallpox and similar viruses. Then, in 1980, smallpox was officially considered eradicated. It is possible, however, for smallpox to be used as a biological weapon.

Before the eradication of smallpox, you could get the virus from close face-to-face interactions with someone infected with the disease. People with smallpox tended to experience fever and spread the virus by coughing or sneezing. They could also spread smallpox from the fluid-containing scabs on their skin. So you could get smallpox if you didn't use gloves to pick up an object (e.g., bedding, clothes) that touched these scabs.

Before its eradication, smallpox could result in death. Three out of 10 people with smallpox would die from this disease—with many of the survivors having large scars on their faces and body that didn't go away. Smallpox could also result in blindness in some people.

Smallpox is caused by the variola (smallpox) virus. This virus belongs to a group of viruses called orthopoxvirus. Other members in this group include vaccinia, mpox (formerly known as monkeypox), and cowpox viruses.

How to Take Tpoxx

The specific directions for Tpoxx vary depending on your weight. In general, however, you'll take the recommended number of Tpoxx capsules by mouth every eight to 12 hours for 14 days. You'll need to take Tpoxx within 30 minutes of meals that have a moderate to a high amount of fat. The meal should contain roughly 25 grams (g) of fat.

If you have trouble swallowing pills, gently pull open the Tpoxx capsules and mix their contents in 30 milliliters (2 tablespoons) of liquid or soft food. Some examples include:

  • Applesauce
  • Chocolate milk
  • Infant (baby) formula
  • Milk
  • Yogurt

Not all of the capsule contents will dissolve in the food. Once you're done mixing the capsule contents into the liquid or soft food, you'll need to take the mixture within 30 minutes.

Some young children between 3 kilograms (6.6 pounds) to 13 kilograms (28.6 pounds) may require Tpoxx intravenous infusions. Older children and adults may also receive these infusions if they can't take anything orally.

As an intravenous (IV) infusion, Tpoxx is usually given every 12 hours for 14 days. Each infusion takes six hours. If you can eat and take your medications by mouth before 14 days, your healthcare provider will likely switch you to Tpoxx capsules. Then you'll finish the remaining 14-day Tpoxx treatment course by taking the capsules.

Storage

You'll need to keep Tpoxx capsules at room temperature between 68 degrees to 77 degrees Fahrenheit—with a short-term safety storage range between 59 degrees to 86 degrees F.

Keep your medications tightly closed and out of the reach of children and pets, ideally locked in a cabinet or closet.

Avoid pouring unused and expired drugs down the drain or in the toilet. Visit the FDA's website to know where and how to discard all unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications.

It's not typically recommended to travel with Tpoxx. If you have an orthopoxvirus infection (e.g., smallpox, mpox) or are exposed to someone with this infection, you should quarantine yourself. This quarantine should be in effect until all of the scabs on your skin have fallen off and you notice that a fresh layer of skin has formed. If you're at your final destination, there might be other regulations. Checking with the U.S. embassy or consulate might be a helpful resource. If you have questions about quarantining or traveling with your medicine, ask your pharmacist or healthcare provider.

How Long Does Tpoxx Take to Work?

Before approval from the Food and Drug Administration (FDA), the effectiveness of Tpoxx wasn't tested in humans for ethical reasons.

Tpoxx was studied in New Zealand white rabbits and cynomolgus monkeys. The rabbits were infected with rabbitpox, and the monkeys were infected with mpox. Both animals were given 14 days of Tpoxx after being infected for a certain number of days. The researchers also ensured that the animals showed symptoms, such as skin lesions (sores), before receiving Tpoxx.

In two rabbit studies, 88% and 90% of rabbitpox-infected rabbits survived after receiving Tpoxx. These rabbits started to receive Tpoxx treatment after being infected for four days.

Based on three monkey studies, 80%, 83%, and 100% of mpox-infected monkeys survived after receiving Tpoxx. These monkeys received Tpoxx treatment after being infected for four days. In another study, Tpoxx also resulted in an 83% survival rate five days after infection. However, six days after infection in a separate study, the survival rate decreased to 50%.

Off-Label Uses

The Centers for Disease Control and Prevention (CDC) states that Tpoxx might be considered for mpox treatment in people with severe mpox infection. Tpoxx might also be appropriate for people with the following risk factors for a severe mpox infection:

  • Immunocompromised (weakened immune system)
  • Children, especially if younger than 8 years old
  • Certain skin conditions, such as atopic dermatitis (eczema) or other skin conditions with excessive shedding
  • Pregnancy
  • Breastfeeding
  • Complications such as bacterial skin infection, severe gastroenteritis (food poisoning or stomach flu), or bronchopneumonia (an infection causing inflammation or swelling of lung airways)
  • Mpox infection in the eyes, mouth, or other areas of the body that can cause some serious problems

What Are the Side Effects of Tpoxx?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Common side effects with Tpoxx capsules may include:

Severe Side Effects

Get medical help immediately if you develop a severe allergic reaction to Tpoxx capsules. Symptoms may include breathing difficulties, an itchy rash, and swelling.

Tpoxx might also lower your blood sugar. This tends to happen if you combine it with a meglitinide medication called Prandin (repaglinide). Repaglinide is a medication option used for type 2 diabetes. Symptoms of low blood sugar include:

  • Extreme hunger
  • Confusion
  • Dizziness
  • Fast heartbeat
  • Irritability
  • Sweating
  • Tremors

Call 911 if your symptoms feel life-threatening.

Long-Term Side Effects

Tpoxx is usually taken for only 14 days. This isn't typically considered long-term use. More research, however, is needed.

Report Side Effects

Tpoxx may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Tpoxx Should I Take?

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The dose of this medicine 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 this medicine. 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 form (capsules):
    • For smallpox:
      • Adults and children weighing 120 kilograms (kg) or more—600 milligrams (mg) (3 capsules) taken 3 times a day for 14 days.
      • Adults and children weighing 40 kg to less than 120 kg—600 milligrams (mg) (3 capsules) taken 2 times a day for 14 days.
      • Children weighing 25 kg to less than 40 kg—400 mg (2 capsules) taken 2 times a day for 14 days.
      • Children weighing 13 kg to less than 25 kg—200 mg (1 capsule) taken 2 times a day for 14 days.
      • Children weighing less than 13 kg—Use and dose must be determined by your doctor.

Modifications

The following modifications (changes) should be kept in mind when using Tpoxx:

Severe allergic reaction: Avoid using Tpoxx if you have a known allergy to it or its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you're unsure.

Pregnancy: In mice and rabbit animal studies, Tpoxx wasn't linked to negative effects on the fetus. However, we don't know enough about the safety and effectiveness of Tpoxx in pregnant people and their unborn fetuses.

Discuss with your healthcare provider if you plan to become pregnant or are pregnant. They will help you weigh the benefits and risks of Tpoxx during your pregnancy.

People with childbearing or reproductive potential: There is no data about Tpoxx's effects on your childbearing or reproductive potential. Male rats, however, did experience reduced fertility from toxicity to the testes (testicles).

Breastfeeding: In animal studies, Tpoxx was present in breast milk. So, it may also be present in human breast milk. However, we don't know enough about the safety and effects of Tpoxx on human breast milk and nursing infants. Since smallpox may spread to the nursing baby through breast milk, breastfeeding isn't recommended.

Talk with your healthcare provider if you plan to breastfeed. They will help you weigh the benefits and risks of Tpoxx while nursing. They can also discuss the different ways available to feed your baby.

Older adults over 65: There are no dosage recommendation changes for older adults. Clinical studies, however, haven't included a large enough number of people in this age group to see whether they respond differently than younger adults. Older adults with several medical conditions or taking several medications should use caution. Some older adults may be more sensitive to side effects from medications.

Children: The Food and Drug Administration (FDA) approved Tpoxx for use in people weighing at least 3 kilograms (6.6 pounds). The effectiveness of Tpoxx in children wasn't tested for ethical reasons, so the effectiveness information was based on animal studies. Dosing information in children is based on weight, which was predicted from data in adults.

Young children weighing between 3 kilograms (6.6 pounds) to 13 kilograms (28.6 pounds) are likely to receive Tpoxx as an intravenous (into the vein) infusion. Healthcare providers will closely monitor your child's kidney function if they get a Tpoxx infusion.

Kidney problems: If you're taking Tpoxx capsules, there's no need to adjust your dosage based on your kidney function. Tpoxx intravenous infusion should be avoided in people with severe kidney impairment.

Immunocompromised: If your immune system (the body's defense system) isn't working well, Tpoxx might be less effective. Your healthcare provider may closely monitor to ensure that Tpoxx is working for you.

Diabetes: Tpoxx might lower your blood sugar levels, especially if you take repaglinide. For this reason, your healthcare provider may closely monitor your blood sugar levels if you take repaglinide for your diabetes.

Missed Dose

If you accidentally forgot your Tpoxx dose, take it as soon as you remember. If it's already within eight hours of your next scheduled dose, then skip the missed dose and take the following dose at your next scheduled dosing time.

Find ways to help yourself remember to keep your appointments and take your medication routinely. If you miss too many doses, Tpoxx might be less effective.

Overdose: What Happens If I Take Too Much Tpoxx?

There is limited information available about Tpoxx overdoses.

If you think that you're experiencing an overdose or life-threatening symptoms, however, seek immediate medical attention.

What Happens If I Overdose on Tpoxx?

If you think you or someone else may have overdosed on Tpoxx, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Tpoxx, call 911 immediately.

Precautions

Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly and to check for unwanted effects.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Tpoxx?

Before taking Tpoxx, talk with your healthcare provider if any of the following applies to you:

  • Severe allergic reaction: Avoid this medication if you have a severe allergic reaction to Tpoxx or any of its ingredients.
  • Pregnancy: In animal studies, Tpoxx wasn't linked to negative effects on the unborn fetus. In humans, however, there is limited information about Tpoxx safety and its effects on the unborn fetus. Reach out to your healthcare provider to discuss the benefits and risks of Tpoxx during your pregnancy.
  • Breastfeeding: In animal studies, Tpoxx was present in breast milk. So it may also be present in human breast milk, but there is little information about the safety and effects of Tpoxx in nursing infants. Since smallpox may spread to the nursing baby through breast milk, breastfeeding isn't recommended. Talk with your healthcare provider to weigh the benefits and harms of Tpoxx while nursing.
  • Children: The Food and Drug Administration (FDA) approved Tpoxx for people weighing at least 3 kilograms (6.6 pounds). Tpoxx effectiveness information, however, was based on animal studies. Dosing information in children is based on weight, which was predicted from data in adults. Healthcare providers will closely monitor your child's kidney function if your child receives Tpoxx as an intravenous infusion.
  • Older adults over 65 years of age: There are no dosage recommendation changes for older adults. However, little information is available to assess differences in response to Tpoxx in older and younger adults. In general, older adults should use caution.
  • Kidney problems: Your kidney function doesn't affect dosing for Tpoxx capsules. Tpoxx intravenous infusion should be avoided in people with severe kidney impairment.

What Other Medications Interact With Tpoxx?

Use caution when taking Tpoxx with the following medications:

  • Repaglinide is a medication option used to treat type 2 diabetes. Tpoxx may increase repaglinide levels in your body. This may excessively lower your blood sugar levels.
  • Versed (midazolam): Midazolam is often used to help you relax and fall asleep before medical procedures. Tpoxx may lower midazolam levels, making it less effective.
  • Live vaccines: Tpoxx might reduce the effectiveness of live vaccines. Examples of live immunizations include the measles, mumps, and rubella (MMR) vaccine and varicella (chicken pox) vaccine.

Talk with your pharmacist or healthcare provider for more detailed information about medication interactions with Tpoxx.

And be sure to talk with your healthcare provider about any other medicines you take or plan to take, including over-the-counter, nonprescription products, vitamins, herbs, or plant-based medicines.

What Medications Are Similar?

Tpoxx (tecovirimat) is an antiviral medication used to treat smallpox. Other similar medications may include:

  • Cidofovir
  • Tembexa (brincidofovir)

The Food and Drug Administration (FDA) approved tecovirimat and brincidofovir for smallpox. The FDA, however, hasn't approved cidofovir for smallpox yet.

All of these medications successfully stopped the smallpox virus from multiplying in a lab setting. They were also effective in animals infected with viruses similar to smallpox. While they have been given to healthy people, they haven't been used to treat smallpox in humans. Brincidofovir and cidofovir have been given to people who were sick from other viral infections.

As of 2021, tecovirimat and cidofovir are being stockpiled in case of a public health emergency in the United States. While brincidofovir is FDA-approved, it isn't currently available in this stockpile.

Frequently Asked Questions

  • Where is Tpoxx available?

    Tpoxx isn't typically available at your local retail pharmacy. To receive Tpoxx, your healthcare provider or certain pharmacists will need to call the state or local health department. They may also contact the Centers for Disease Control and Prevention (CDC) emergency operation center via phone at 770-488-7100 or e-mail at Poxvirus@cdc.gov.

  • Does the CDC need to receive required forms and information before I can take Tpoxx?

    No. You can start receiving Tpoxx treatment after filling out the informed consent paperwork.
    Your healthcare provider will need to fill out some more forms, which can be sent back to the CDC after you start your treatment.

    Your healthcare provider might also ask you for some optional information. This is to make sure that Tpoxx is working and to monitor you for side effects.

  • What am I supposed to do if I experience serious side effects from Tpoxx?

    Let your healthcare provider know right away. They will advise you on what to do next. They will also fill out a form and e-mail it to the CDC.

  • Since Tpoxx data in humans are limited, will there be more studies?

    The Food and Drug Administration (FDA) does want more clinical trials with Tpoxx.

How Can I Stay Healthy While Taking Tpoxx?

If you're taking Tpoxx, chances are smallpox or mpox has been negatively affecting your quality of life. Having one of these infections does have its challenges. You may have tried different approaches or treatments.

The following are some general suggestions on what to do if you get smallpox or mpox and how to keep these infections from spreading. There are also tips to protect yourself from getting these infections.

  • Take smallpox or mpox-related medications as recommended by your healthcare provider.
  • Cover your face when sneezing or coughing.
  • Consider wearing a face mask.
  • Wash your hands with soap and water often.
  • Avoid touching your eyes, nose, and mouth with your hands.
  • Keep your distance if you or someone else has smallpox or mpox.
  • Stay home until all of the scabs on your skin have fallen off and you notice that a fresh layer of skin has formed.
  • Cover up your rash.
  • Don't touch anyone's rash.
  • Don't share objects (e.g., eating utensils) with someone with smallpox or mpox.
  • Clean high-touch surfaces and objects, such as doorknobs, light switches, and tables.
  • Wear gloves if you need to touch objects someone with smallpox or mpox has already touched.
  • Don't travel if you have smallpox or mpox.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  9. Centers for Disease Control and Prevention. Monkeypox: treatment information for healthcare professionals.

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By Ross Phan, PharmD, BCACP, BCGP, BCPS
Ross is a writer for Verywell with years of experience practicing pharmacy in various settings. She is also a board-certified clinical pharmacist and the founder of Off Script Consults.