As the monkeypox outbreak continues to intensify, it's not just vaccines for the virus that are in short supply. There's just one drug currently available that can be used to treat monkeypox—TPOXX—and obtaining it has also proved challenging.
TPOXX (short for tecovirimat), was originally approved by the Food and Drug Administration (FDA) to treat smallpox, which is an orthopoxvirus in the same family as monkeypox. The drug can also be prescribed to patients who have monkeypox or are at high risk of getting a severe case of the monkeypox virus.
“It’s shown some potential activity against monkeypox infections,” says Adi Shah, an infectious disease specialist at Mayo Clinic, told Health.
TPOXX is not available in pharmacies however. It can only be obtained through the country's Strategic National Stockpile or from state health and territorial departments. And while TPOXX may be effective in treating monkeypox, it isn't for everyone. Experts are still learning about the drug's effectiveness.
Here's what you need to know about the antiviral drug TPOXX and its use in treating monkeypox.
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What Is TPOXX?
A drug initially aimed at smallpox, TPOXX works by blocking interactions between viral proteins so the virus can't replicate, which can resolve pox symptoms and prevent community spread.
In 2018, the Food and Drug Administration (FDA) approved TPOXX to treat smallpox under the “Animal Rule,” which allows testing a drug on animals rather than humans. While the FDA has not specifically approved TPOXX for monkeypox treatment, some animal studies suggest it may be an effective, safe way to mitigate people’s monkeypox symptoms.
“You can do experiments with animals with the same— or very similar viruses— and know that if it works, it’s probably going to work in humans,” Michael Angarone, DO, an infectious disease specialist at Northwestern Medicine, told Health.
As a result, the CDC has allowed TPOXX treatment for certain monkeypox patients under what’s sometimes referred to as the “compassionate use protocol.” This protocol provides expanded access to drugs for patients who have an immediately life-threatening condition or serious disease, according to the FDA.
What Does TPOXX Treatment Involve?
TPOXX is an oral medication. Patients typically take three, 200-milligram capsules by mouth, twice a day, for 14 days. Patients with morbid obesity, however, may need to take the same dose three times a day, Justin Moore, PharmDe, an infectious diseases clinical pharmacist at Northwestern Medicine, told Health.
Common side effects of TPOXX include stomach upset, nausea and vomiting, headache, and low blood sugar in diabetic patients who take glucose-lowering medication. "Otherwise, it's fairly well tolerated," Moore said.
TPOXX is also available through IV, which is usually given to people who can't swallow a pill. This may be necessary if an individual is unresponsive, or has lesions in their mouth that make swallowing difficult. "The oral formulation is preferred because it is easier to get, and it doesn't require hospitalization," says Dr. Shah. In addition, the IV version of TPOXX can cause adverse skin reactions at the site of the injection, on top of already painful Monkeypox lesions.
Where Is TPOXX Available? And Why Is It so Difficult to Find?
Obtaining TPOXX isn't as easy as going to the doctor and asking for a prescription. Because the drug is technically FDA-approved for smallpox and not monkeypox, Moore says the CDC keeps a national stockpile of the medication that it distributes to local health departments on an as-needed, by-request basis.
Healthcare providers in any state can prescribe TPOXX to anyone diagnosed with monkeypox, but the process is lengthier. "Because the supply is governed by the federal government in conjunction with state or local health departments, there are a few logistical steps to getting this medication," says Dr. Shah. Providers usually reach out to their local or state health department to request the drug for a patient. Then, Dr. Shah says the department requests the drug from the CDC. Usually patients are able to begin treatment within about 24 to 48 hours.
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Is TPOXX Really Effective for Monkeypox Treatment?
Thus far, TPOXX appears to be useful in treating monkeypox. Animal data suggests TPOXX lowers the chances of disease mortality when given soon after diagnosis, according to the CDC.
When researchers administered non-human primates and rabbits lethal doses of monkeypox, more than 90% of animals treated with TPOXX survived. The placebo, on the other hand, only had a survival rate of 1 in 20. A few human studies, such as one published in Lancet, have confirmed the drug’s effectiveness in safely reducing the course of illness in infected patients.
Still, research is ongoing and in the few human studies that have taken place, there was no control group to compare TPOXX to —so presently, experts are relying on anecdotal evidence about how well it works.
"In the small numbers of people who have received it for monkeypox in the past and during the current outbreak, symptoms usually start to get better within a few days to a week of starting it," says Angarone.
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