Tecovirimat for Smallpox

Tecovirimat is an antiviral drug that is used in children and adults for the treatment of smallpox (caused by variola infection). Smallpox has been eradicated throughout the world, however, Variola, the causative agent of smallpox disease, is still contained in some research laboratories. It may re-emerge because of incidental exposure in the laboratory personnel or as a result of bioterrorism.

Tecovirimat dose in Adults

Tecovirimat dose in the treatment of Smallpox:

  • 600 mg orally two times a day for 14 days

Tecovirimat dose in Children

Tecovirimat dose in the treatment of Smallpox disease:

  • 13 to 24 kg:

    • 200 mg orally two times a day for 14 days
  • 25 to 39 kg:

    • 400 mg orally two times a day for 14 days
  • more than 40 kgs:

    • 600 mg orally two times a day for 14 days

Pregnancy Risk Factor: C

  • Animal reproduction studies have not shown any adverse fetal events.
  • It has not been proven to be effective in human pregnancy.
  • Smallpox infection may also occur in fetus and may make it more difficult for pregnant women to get the disease.

Use during breastfeeding:

  • It is unknown if the drug will be excreted into breast milk.
  • Manufacturers recommend weighing the benefits and risks for the mother and infant.

Tecovirimat dose in Renal Disease:

Adjustment in the dose is not necessary.

Tecovirimat dose in Liver Disease:

Adjustment in the dose is not necessary.

Common Side Effects of Tecovirimat:

  • Central Nervous System:

    • Headache

Less Common Side Effects of Tecovirimat:

  • Cardiovascular:

    • Increased Heart Rate
  • Central Nervous System:

    • Abnormal Electroencephalogram
    • Chills
    • Depression
    • Disturbance In Attention
    • Dysphoria
    • Irritability
    • Malaise
    • Migraine
    • Pain
    • Panic Attack
    • Paresthesia
  • Dermatologic:

    • Cheilosis
    • Facial Erythema
    • Facial Swelling
    • Pruritic Rash
    • Pruritus
    • Skin Rash
  • Endocrine & Metabolic:

    • Increased Thirst
  • Gastrointestinal:

    • Nausea
    • Abdominal Pain
    • Vomiting
    • Dysgeusia
    • Dyspepsia
    • Eructation
    • Oral Paresthesia
    • Xerostomia
    • Diarrhea
    • Mild Gastric distress
  • Hematologic & Oncologic:

    • Decreased Hematocrit
    • Decreased Hemoglobin
    • Purpuric Rash
  • Neuromuscular & Skeletal:

    • Arthralgia
    • Osteoarthritis
  • Respiratory:

    • Oropharyngeal Pain
  • Miscellaneous:

    • Fever

Contraindications to Tecovirimat Include:

The manufacturer has not listed any contraindications.


  • Blood glucose,
  • Features of hypoglycemia when co-administered with repaglinide.

Tecovirimat (United States: Availability limited to CDC distribution from the strategic national stockpile in consultation with local health department): Drug Interaction

Tecovirimat for Smallpox


CYP3A4 Inducers (Weak) may decrease the serum concentration of CloZAPine.


Tecovirimat may decrease the serum concentration of Midazolam.


CYP3A4 Inducers (Weak) may decrease the serum concentration of NiMODipine.


Tecovirimat may increase the serum concentration of Repaglinide.

Smallpox Vaccine Live

Tecovirimat may diminish the therapeutic effect of the Smallpox Vaccine Live.

Risk Factor D (Consider therapy modification)


CYP2C19 Inhibitors may increase the serum concentration of Cilostazol. Management: Consider reducing the cilostazol dose to 50 mg twice daily in patients who are also receiving inhibitors of CYP2C19.

How to administer Tecovirimat?

  • It is administered orally within half an hour after a meal.
  • If the patient can not swallow, the capsule may be opened and the contents mixed with 30 ml of liquid like milk, chocolate milk, infant formula or soft food like applesauce, and yogurt.
  • The powder may not completely dissolve. After mixing, the solution should be administered within 30 minutes of the preparation.

Mechanism of action of Tecovirimat:

  • It blocks the activity of the orthopoxvirus-VP37 protein, and also prevents its interaction with cell Rab9 GTPase or TIP47.
  • This prevents the formation of egress competent enveloped viruses that are necessary for virus dissemination.
  • 77 to 82% of drug is protein-bound. It is metabolized through hydrolysis of the ammonium bond and glucuronidation (UGT1A1, UGT1A4).
  • It has a 20 hour half-life. It takes approximately 4 to 6 hours to reach peak serum concentration. 
  • 73% of drug is excreted through the urine as metabolites, while 23% is excreted unchanged in the feces.