Merck vs. Pfizer's COVID-19 antiviral pills: 11 notes

While the FDA has greenlit the use of COVID-19 antiviral pills made by Merck and Pfizer, there are differences in the authorizations for each. The supplies of both remain limited

Eleven notes: 

Pfizer's Paxlovid

1. The FDA issued an emergency use authorization for Pfizer's antiviral pill regimen, Paxlovid, Dec. 22, making it the first available at-home COVID-19 treatment. 

2. The treatment is administered as three tablets (two tablets of nirametrelvir and one tablet of ritonavir) taken twice daily for no more than five consecutive days. 

3. The authorization for Paxlovid is broader than Merck's molnupiravir. Paxlovid is authorized for use in patients 12 and older who weigh at least 88 pounds and are at high risk of progressing to severe illness. 

4. The pill regimen reduced the risk of hospitalization or death by 89 percent in high-risk adults in a trial. Pfizer on Jan. 18 also said Paxlovid appears effective against omicron, based on initial laboratory findings. 

5. The Institute for Safe Medication Practices on Jan. 3 alerted pharmacists that patients with severe renal impairment should not receive the drug, while those with moderate renal impairment should receive a dose reduction. The alert also warned of other potential error risks with Paxlovid, such as patients accidentally failing to take both tablets together and drug interactions. 

6. Pfizer expects to produce at least 120 million courses of Paxlovid this year for global customers. The U.S. has purchased 20 million courses of the treatment, with the first 10 million courses set to be delivered by the end of June. 

Merck's molnupiravir 

7. The FDA authorized Merck's molnupiravir Dec. 23. The authorization was more limited, meant for those 18 and older who are at high risk of developing severe illness when alternative treatments are "not accessible or clinically appropriate." It was not authorized for younger patients because the drug may affect bone and cartilage growth. 

8. The treatment consists of 40 pills taken over five days. 

9. A final analysis showed the drug, developed by Merck and Ridgeback Therapeutics, reduced the risk of hospitalization or death among high risk-patients by 30 percent, down from 48 percent in an earlier analysis. 

10.  A panel of FDA advisors narrowly on Nov. 30 narrowly voted to recommend the agency authorize molnupiravir, with some members citing efficacy and safety concerns such as pregnancy risks as reasons to vote against recommendation.  

11. The U.S. has purchased 3 million courses of molnupiravir.

 

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