tecovirimat
Brand names: Tpoxx
Tpoxx is an antiviral medicine used to treat smallpox. It works by stopping the smallpox virus from spreading in your body.
What it does
Tpoxx is used to treat smallpox in adults and children who weigh at least 7 pounds.
Common side effects
Headache, Nausea, Stomach pain
Key warnings
If you have kidney problems, use the injection with caution.
How It Works
Tpoxx blocks a protein called VP37 on the smallpox virus. This protein helps the virus to spread. By blocking VP37, Tpoxx stops the virus from wrapping itself and infecting other cells.
How to Take It
Tpoxx comes as a capsule or as an injection into your vein. If you weigh 88 pounds or more, you will likely take 3 capsules every 12 hours for 14 days. Take the capsules within 30 minutes after eating a full meal that contains fat. If you miss a dose, take it as soon as you remember unless it is almost time for your next dose.
Pregnancy & Breastfeeding
There is not enough information about Tpoxx use in pregnant women to know if it is safe. Breastfeeding is not recommended if you have smallpox because the virus can spread to your baby through breast milk.
Missed Dose
If you miss a dose of Tpoxx capsules, take it as soon as you remember if it is within 8 hours of your scheduled dose. If it is less than 8 hours until your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store Tpoxx capsules at room temperature, away from heat and moisture. Store Tpoxx injection in the refrigerator and do not freeze.
Serious Warnings
If you have kidney problems, use the injection with caution. If you have severe kidney problems (creatinine clearance below 30 mL/min), you should not use the Tpoxx injection. When taking Tpoxx with repaglinide, monitor your blood sugar for hypoglycemia.
Known Drug Interactions
7.3 Drugs Without Clinically Significant Interactions With TPOXX Based on a drug interaction study, no clinically significant drug interactions have been observed when TPOXX is co-administered with bupropion, flurbiprofen, or omeprazole [see Clinical Pharmacology ( 12.3 )] .
Mechanism: There are no significant interactions between these two drugs based on medical studies.
What to do: You can take these medications together as prescribed by your doctor.
7.3 Drugs Without Clinically Significant Interactions With TPOXX Based on a drug interaction study, no clinically significant drug interactions have been observed when TPOXX is co-administered with bupropion, flurbiprofen, or omeprazole [see Clinical Pharmacology ( 12.3 )] .
Mechanism: Research shows that taking these two drugs together does not cause any meaningful changes in how they work.
What to do: No dosage adjustments or extra monitoring are necessary when using these drugs together.
CNS Depressant: Midazolam b ↓ midazolam Monitor for effectiveness of midazolam.
Mechanism: Tecovirimat causes the body to process midazolam faster, which lowers the amount of medicine in your system.
What to do: Your doctor should check to see if the midazolam is still working effectively for you.
Concomitant Drug Class: Drug Name Effect on Concentration a Clinical Effect/Recommendation Blood Glucose-Lowering Agent: Repaglinide b ↑ repaglinide Monitor blood glucose and monitor for hypoglycemic symptoms in patients when TPOXX is co-administered with repaglinide [see Warnings and Precautions ( 5.1 )] .
Mechanism: Tecovirimat increases the amount of repaglinide in your blood, which can cause your blood sugar to drop too low.
What to do: You should check your blood sugar often and watch for signs of low blood sugar.
Common Questions
Can I take Tpoxx on an empty stomach?
How long will I need to take Tpoxx?
What should I do if I vomit after taking a dose of Tpoxx?
Can Tpoxx interact with other medications I am taking?
Will Tpoxx prevent me from spreading smallpox to others?
What if I have trouble swallowing capsules?
Can I get a smallpox vaccine while taking Tpoxx?
What are the ingredients in Tpoxx capsules?
What should I do if I experience side effects while taking Tpoxx?
Is Tpoxx a cure for smallpox?
What are the common side effects of tecovirimat?
Does tecovirimat interact with other medications?
What drug class is tecovirimat?
Is tecovirimat safe during pregnancy?
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What the FDA Data Shows for tecovirimat
The FDA label for tecovirimat (sold under brand names such as Tpoxx) classifies it as a prescription-only medication in the VP37 Inhibitor (Antiviral) class. Tpoxx is used to treat smallpox in adults and children who weigh at least 7 pounds. Official labeling lists 5 commonly reported side effects, including Headache, Nausea, Stomach pain.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. Voluntary reports accumulate over the lifetime of a drug and reflect wide-ranging clinical use. The database also lists 4 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated minor severity. Acquisition-cost data is surveyed weekly by CMS and updated as manufacturers report changes.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: December 31, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages