As of December 23, 2021, the U.S. Food and Drug Administration (FDA) has granted emergency use authorization (EUA) for two new antiviral medications to treat mild to moderate COVID-19 illness. Pfizer’s Paxlovid® and Merck’s Molnupiravir® are available in a convenient pill form and can be taken at home. They are only available to those at high risk of severe illness, however, and require a doctor’s prescription. 

Who Is Eligible for This Treatment?

Eligibility criteria differ for each of the treatments. Criteria for Paxlovid include:

• Having tested positive for COVID-19 but not having been admitted to the hospital
• Being at high risk for developing severe COVID-19
• Being at least 12 years old and weighing at least 88 pounds
  

Criteria for Molnupiravir include:

• Having tested positive for COVID-19 but not having been admitted to the hospital
• Being at high risk for developing severe COVID-19 
• Not having access to an alternative FDA-authorized COVID-19 treatment option or none that is clinically appropriate 
• Being at least 18 years old
  

Speak with your doctor about your eligibility, as well as which option might be best for your specific situation and care needs. 

What Are the Differences between Paxlovid and Molnupiravir?

The goal of both Paxlovid and Molnupiravir is to prevent the SARS-CoV-2 virus from replicating properly. If the virus can’t replicate, the viral load and symptom severity remain low. Since both antivirals are only intended for mild to moderate COVID-19 illness, the pills need to be taken as close to your infection date as possible and not more than five days after symptom onset. The pills differ in how they work and how they are administered. 

Paxlovid is actually two pills taken together (nirmatrelvir and ritonavir):

• Nirmatrelvir interferes with the function of key proteins that the virus needs in order to replicate. 
• Ritonavir prevents nirmatrelvir from being broken down before it has done its job.

A Paxlovid course consists of three tablets (two tablets of nirmatrelvir and one tablet of ritonavir) taken together orally twice a day for five days. In clinical trials, Pavlovid taken in this dosage reduced COVID-19-related hospitalizations by nearly 90%.

Molnupiravir inserts flaws into the virus’s genetic code, rendering it unable to replicate itself accurately. A Molnupiravir regimen consists of taking four tablets by mouth every 12 hours for five days. In clinical trials, Molnupiravir decreased COVID-19-related hospitalizations by 30%.

What Are the Potential Side Effects of the COVID-19 Antiviral Pills?

Both antivirals can potentially interfere with other medications and impact pre-existing health conditions, as well cause side effects of their own. 

Potential side effects of Paxlovid include:

• Diarrhea
• High blood pressure
• Muscle aches
• Taste dysfunction
  

Paxlovid is also not recommended for people with severe kidney or liver damage.

Side effects of Molnupiravir may include:

• Diarrhea
• Dizziness
• Nausea
  

Molnupiravir is also not recommended for use during pregnancy. Speak with your doctor to weigh the benefits against the known risks. 

Neither Paxlovid nor Molnupiravir is authorized for COVID-19 prevention, and neither serves as a substitute for vaccination. If you’ve recently tested positive for COVID-19 and you meet the eligibility criteria for either of the antivirals, contact your healthcare provider immediately to discuss a prescription. 

*McCallum, K. (2021, Dec. 28). How Do COVID-19 Antiviral Pills Work & Who Is Eligible to Receive Them? Houston Methodist.   https://www.houstonmethodist.org/blog/articles/2021/dec/how-do-covid-19-antiviral-pills-work-who-is-eligible-to-receive-them/

Much about the novel coronavirus, i.e., COVID-19, is still not fully understood. As research progresses and our knowledge of the virus increases, information can change rapidly. We strive to update all of our articles as quickly as possible, but there may occasionally be some lag between scientific developments and our revisions.