Everything you need to know about Paxlovid

It’s the first oral treatment for COVID-19, and could be a pandemic game-changer

By Cheryl Maguire | Updated on Mar. 4, 2022 Medically reviewed by Marissa Walsh, Pharm.D., BCPS-AQ ID

CORONAVIRUS UPDATE: As experts learn more about the novel coronavirus, news and information changes. For the latest on the COVID-19 pandemic, please visit the Centers for Disease Control and Prevention (CDC).

President Joe Biden announced the shipment of the new COVID-19 antiviral drug Paxlovid (nirmatrelvir / ritonavir) when he addressed the nation on Jan. 4, 2022. The new “COVID pill” is manufactured by Pfizer and was given emergency use authorization (EUA) on December 22, 2021 by the U.S. Food and Drug Administration (FDA). It is the first oral drug authorized for the novel coronavirus. The second one, created by Merck & Co and Ridgeback Biotherapeutics is molnupiravir. Molnupiravir received its EUA the day after Paxlovid.

“They’re a game changer and have the potential to dramatically alter the impact of COVID-19, the impact it’s had on this country and our people,” President Biden said in his address.

What is Paxlovid?

Paxlovid is an antiviral pill taken orally to treat mild to moderate COVID-19 in patients at risk of developing a more severe infection. It is a combination of nirmatrelvir (PF-07321332) and ritonavir. Nirmatrevlir prevents the virus from replicating while ritonavir is known as a “booster,” which helps increase levels of nirmatrelvir in the body to those that are effective against SARS-CoV-2. Ritonavir (a protease inhibitor) has historically been used in the management of HIV, while nirmatrelvir is a new medication. Paxlovid works similarly to how Tamiflu (oseltamivir) works for influenza (the flu) infections. A Pfizer study found that use of Paxlovid, in patients at risk for severe illness, reduced risk of hospitalization or death by 89%.

“Viruses like SARS-CoV-2 that cause COVID-19 need to replicate, or copy themselves, in order to spread in the body,” says William Li, MD, physician, scientist, and author of Eat To Beat Disease. “The more they copy, the more virus is around, and the more severe the infection. Paxlovid is an antiviral agent that blocks the virus from copying itself. It is like jamming the toner cartridge in a copy machine. You cannot make a copy once it’s jammed.”

Dosage

Pfizer’s Paxlovid is only approved for use for adults and children aged 12 and older who weigh at least 88 pounds. This treatment of COVID-19 is used after you develop COVID-19 symptoms and test positive. Paxlovid does not prevent infection. COVID-19 vaccines are the best way to avoid illness. This drug should be taken as soon as possible, but at most five days of symptom onset and can be taken at home.

Paxlovid consists of two different drugs—nirmatrelvir and ritonavir—that are packaged together. Each dose is 300 mg of nirmatrelvir (two oval, pink 150 mg tablets) and one tablet of 100 mg of ritonavir (one ovaloid, white 100 mg tablet). The dose is the same for all ages. You may require a lower dose if you have kidney disease. Paxlovid is taken by mouth in the morning and at night for five days. All three pills should be taken together, twice a day.

Side effects

Paxlovid is a new COVID medication that only a limited number of people have taken. Even though this drug has been researched and proven more effective than placebo in clinical trials, there may be side effects that did not appear in the test subjects. If you experience any side effects, contact your healthcare provider. Paxlovid can cause a multitude of serious drug interactions with other medications and vitamins like St. John’s Wort. Make sure to tell your healthcare provider about all medications and vitamins that you currently take. You may be advised to modify dosages of other medications, stop taking them altogether for the time you’re taking Paxlovid, or in limited situations be advised against taking Paxlovid. Here are some possible serious side effects:

Liver problems: Symptoms related to liver problems are loss of appetite, yellowing of your skin and the whites of eyes (jaundice), dark-colored urine, pale colored stools, itchy skin, and abdominal pain.
Resistance to HIV medicines: If you have untreated HIV infection Paxlovid may make some HIV medicines ineffective when you seek treatment.

These are also some less serious side effects:

Altered sense of taste
Diarrhea
High blood pressure
Muscle aches

Contraindications and restrictions

Paxlovid is not for everyone. Some restrictions apply to certain medical conditions. Ritonavir may cause liver damage, so if someone has liver issues such as preexisting liver diseases, liver enzyme abnormalities, or liver inflammation they may not be able to take Paxlovid. Also, if you have severe kidney problems Paxlovid is not recommended. You should not take Paxlovid if you are allergic to nirmatrelvir, ritonavir, or any of the ingredients in Paxlovid. If you are pregnant or breastfeeding, there has not been research about how this medication may affect you or your baby. Discuss your options with your prescribing physician or pharmacist.

It is also not recommended that you take Paxlovid if you are taking any of the following medicines because of the risk for drug interactions:

Alfuzosin
Pethidine, piroxicam, propoxyphene
Ranolazine
Amiodarone, dronedarone, flecainide, propafenone, quinidine
Colchicine
Lurasidone, pimozide, clozapine
Dihydroergotamine, ergotamine, methylergonovine
Lovastatin, simvastatin
Revatio (sildenafil) for pulmonary arterial hypertension (PAH)
Triazolam, oral midazolam
Apalutamide
Carbamazepine, phenobarbital, phenytoin
Rifampin
St. John’s Wort

When will Paxlovid be available?

“This is a new product that is not widely available in regular cities due to supply,” says Banita Sehgal, MD, a physician at LifeMD in California. “Many emergency rooms have initial access to it.”

Paxlovid is now available for limited use for patients with mild to moderate COVID-19 symptoms who are within five days of symptoms and who have risk factors for the progression to severe disease. Hopefully, Paxlovid will be more widely available in the coming months. But the drug takes a long time to manufacture which may slow down the distribution process.

Since Paxlovid is a COVID-19 pill that patients can easily swallow and take at home, the medication requires less training for healthcare providers as opposed to monoclonal antibodies therapy that needs to be administered by an intravenous (IV) infusion.

Where to buy Paxlovid

Currently Paxlovid is being distributed to states throughout the country. Paxlovid must be prescribed, but where you pick up that prescription varies by state since supplies are limited. In New York City, a specific company delivers the prescription to your home. In other states, a prescription can be filled at local healthcare centers.

How much does Paxlovid cost?

The federal government purchased 20 million treatment courses of Paxlovid—costing about $530 per course. Currently, Paxlovid is free for the public since it was purchased by the federal government for public health during the pandemic. In the future, insurance might cover the cost.

Other COVID treatment updates

These are the current therapeutics for COVID-19 that are available but might be in limited supply or limited to high-risk patients:

Dexamethasone is a corticosteroid used to treat patients with anti-inflammatory issues like arthritis. This medication is used to help severe COVID-19 patients who are on a ventilator or need oxygen in the hospital to recover.
Remdesivir, was the first treatment to be approved for hospitalized patients diagnosed with COVID-19. Originally the medication was being investigated to treat hepatitis C and has also demonstrated some efficacy in treating Ebola and Marburg virus infections. The FDA expanded the approval indications on Jan. 21, 2022 for using remdesivir as an outpatient treatment.
Monoclonal antibodies (MAb) are created in a laboratory to mimic antibodies you naturally create to fight off infections. Monoclonal antibody therapy is used when someone has already tested positive for COVID-19 and is at high risk for developing serious symptoms. Three different MAb treatments have been authorized to prevent severe disease in those already infected (bamlanivimab with etesevimab, casirivimab with imdevimab, and sotorovimab). This form of treatment is most effective when given early—when the person first shows symptoms. On Feb. 11, 2022, the FDA issued an EUA for yet another monoclonal antibody for treatment of mild to moderate COVID-19, known as bebtelovimab. The dose is a single 175 mg injection, which can be administered in those at high risk of progressing to severe disease within seven days of symptom onset. Data on efficacy of these monoclonal antibodies against circulating variants and subvariants is always evolving, and may make certain MAbs preferable for treatment over others.
Evusheld is a type of monoclonal antibodies given emergency use authorization to prevent infection with COVID-19 for people who are at high risk of severe COVID-19 and who may not have a good immune response from the vaccine or cannot be vaccinated. It’s not a substitute for vaccination.
Molnupiravir is an antiviral medication for COVID-19 similar to Paxlovid. The medication was co-developed by the pharmaceutical companies Merck & Co and Ridgeback Biotherapeutics. On Dec. 23, 2021 the medication received emergency use authorization and became the second authorized antiviral treatment for COVID-19. Similar to Paxlovid you take the medication at home for 5 days within 5 days of the onset of symptoms. But the medications work differently. “Paxlovid inhibits viral replication whereas molnupiravir causes lethal mutations in the virus so it eventually dies out,” says Noha Polack, MD, a pediatrician at Progressive Pediatrics in Union City, New Jersey. Paxlovid has been approved for children 12 years and older whereas molnupiravir has only been approved for people 18 years and older. Paxlovid has shown to be 89% effective in preventing hospitalization or death whereas molnupiravir is 30% effective in preventing the same composite outcome.