How does this medication work? What will it do for me?

Tecovirimat belongs to the class of medications called antivirals. It is used to treat human smallpox in adults and children weighing at least 13 kg.

This medication works by preventing the virus that causes human smallpox from reproducing. This prevents the virus from spreading in the body and allows time for your body to build up protection against the virus.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each hard gelatin, opaque, orange and black, size “0” capsule, imprinted with white ink with “SIGA” and the SIGA symbol followed by “®” on an orange body and “ST-246Ò” on the black cap, contains 200 mg of tecovirimat (as tecovirimat monohydrate). Nonmedicinal ingredients: colloidal silicon dioxide, croscarmellose sodium, hydroxypropyl methylcellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and sodium lauryl sulfate; capsule shell: gelatin, FD&C Blue No. 1, FD&C Red No. 3, FD&C Yellow No. 6, and titanium dioxide; printing ink: ammonium hydroxide, isopropyl alcohol, n-butyl alcohol, propylene glycol, simethicone, shellac, and titanium dioxide.

How should I use this medication?

The recommended dose of tecovirimat depends on body weight.

The usual dose for adults and children weighing between 40 kg and 120 kg is 600 mg (3 × 200 mg capsules) taken by mouth twice a day for 14 days. People weighing more than 120 kg should take 600 mg 3 times a day for 14 days. The dose for children and adolescents weighing 13 kg to less than 25 kg is 200 mg taken twice a day. For people weighing 25 kg to less than 40 kg, the usual dose is 400 mg (2 × 200 mg capsules) twice a day.

Tecovirimat should be taken within 30 minutes after a full meal that is moderate to high in fat (approximately 25 grams of fat). Finish all of this medication, even if you have started to feel better.

For people who are not able to swallow capsules, the capsules may be opened and mixed with 30 mL of fluid, such as milk or chocolate milk. Alternatively, the contents of the capsules may be sprinkled on soft food such as yogurt or applesauce. Consume the food or fluid within 30 minutes of preparing the dose.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you are allergic to tecovirimat or any ingredients of the medication.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal pain
  • belching or burping
  • change in taste sensation
  • chapped lips
  • constipation
  • diarrhea
  • dizziness
  • dry mouth
  • fatigue or tiredness
  • feeling uneasy or dissatisfied
  • general feeling of being unwell
  • headache
  • heartburn
  • irritability
  • joint pain or stiffness
  • nausea
  • pain
  • thirst
  • trouble concentrating
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • chills
  • facial swelling, redness, or itchiness
  • fever
  • increased heart rate
  • mouth pain
  • red or purple spots on the skin that do not turn white under pressure
  • signs of anemia (low red blood cells; e.g., dizziness, pale skin, unusual tiredness or weakness, shortness of breath)
  • signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
  • symptoms of panic attack (e.g., feeling of loss of control, danger, shortness of breath, shaking)
  • tingling or numbness in the hands, feet, or mouth

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Heart rhythm: Tecovirimat can cause changes to the normal rhythm of the heart, including an irregular heartbeat called QT prolongation. QT prolongation is a serious life-threatening condition that can cause fainting, seizures, and sudden death. If you are at risk for heart rhythm problems (e.g., people with heart failure, angina, low potassium or magnesium levels), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if tecovirimat passes into breast milk. If you are breast-feeding and taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children weighing less than 13 kg.

What other drugs could interact with this medication?

For a full list of interactions, use the Drug Interaction Checker available on the website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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