EXPLAINER: COVID-19 pills must be taken within 5 days

Newly infected COVID-19 patients have two treatment options that can be taken at home. But that convenience comes with a catch: The pills have to be taken as soon as possible once symptoms appear.

The challenge is getting tested, obtaining a prescription and starting the pills in a short window.

U.S. regulators authorized Pfizer's pill, Paxlovid, and Merck’s Lagevrio late last year. In high-risk patients, both were shown to reduce the chances of hospitalization or death from COVID-19, although Pfizer's was much more effective.

A closer look:

WHO SHOULD TAKE THESE PILLS?

The antiviral pills aren’t for everyone who gets a positive test. They are intended for those with mild or moderate COVID-19 who are more likely to become seriously ill. That includes older people and those with other health conditions like heart disease, cancer or diabetes that make them more vulnerable.

Both pills were OK'd for adults, while Paxlovid also is authorized for children ages 12 and older.

WHO SHOULDN'T TAKE THESE PILLS?

Merck’s Lagevrio is not authorized for children because it might interfere with bone growth. It also isn't recommended for pregnant women because of the potential for birth defects.

Pfizer's pill isn't recommended for patients with severe kidney or liver problems. It also may not be the best option for some because it may interact with other medications.

The antiviral pills aren't authorized for people hospitalized with COVID-19.

WHAT'S THE TREATMENT WINDOW?

The pills have to be started as soon as possible, within five days of the start of symptoms. Cough, headache, fever, the loss of taste or smell and muscle and body aches are among the more common signs. The Centers for Disease Control and Prevention offers a website to check your symptoms.

Dr. Cameron Wolfe, an infectious disease specialist at Duke University Hospital, advises getting a test as soon as you have symptoms of COVID-19.

“If you wait until you have started to get breathless, you have already to a large extent missed the window where these drugs will be helpful,” Wolfe said.

WHERE CAN YOU GET THE PILLS?

Pharmacies, community health centers, hospitals and urgent care centers are among the sites stocking the antiviral pills, but prescriptions must come from a doctor or other authorized health worker.

The oral treatments are currently available in about 20,000 locations around the country, but President Joe Biden's administration expects that total to jump to around 40,000 in the next few weeks.

The administration also is working to expand the number of sites that can test patients and then provide the treatments in one visit. There are currently 2,200 of these so-called test-to-treat sites, including all 1,200 MinuteClinic locations inside CVS drugstores. Patients can find find test-to-treat locations by checking the U.S. government's COVID.gov website.

Supplies of the pills were limited initially, but ample amounts are now available.

ARE THERE OTHER OPTIONS FOR NEW COVID-19 PATIENTS?

Yes, but it isn’t as easy to use as a pill.

In February, the Food and Drug Administration authorized a new injected drug from Eli Lilly, bebtelovimab, that targets the omicron variant with virus-fighting antibodies. Regulators cleared that drug for adults and adolescent patients with mild-to-moderate cases of COVID-19 who are at high risk of hospitalization and death.

Earlier this year, regulators revoked emergency use authorization for another Lilly treatment and drugs from Regeneron and GlaxoSmithKline because they were no longer effective against the evolving virus.

WHAT OTHER TREATMENTS MIGHT BE COMING?

Japanese drugmaker Shionogi is testing another antiviral pill.

Unlike Paxlovid, the company’s drug does not require taking a second antiviral to boost its effectiveness against COVID-19. That could reduce some of the potential drug interaction problems associated with the Paxlovid combination.

The Shionogi drug is also designed to be taken once daily for five days. That’s simpler than Paxlovid’s dosing, which must be taken twice daily for five days.

In mid-stage testing Shionogi said its drug significantly reduced COVID-19 viral levels and shedding in patients treated within five days of symptoms. The company is conducting a large global study in patients with increased risk of hospitalization or death due to age or other health issues. Early results from that study — which is being funded by the U.S. National Institutes of Health — are expected by the fall.

The company has already requested approval in Japan and plans to also file applications with regulators in the U.S. and Europe.

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AP Health Writer Matthew Perrone contributed to this report. Follow Tom Murphy on Twitter at @thpmurphy.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.