Pediatric Pearls. "Is Paxlovid safe to take when breastfeeding?"
January 23, 2024
With cases of COVID-19 rising in the Northeast, where I live, a common question I am asked is, “Is Paxlovid safe to take when breastfeeding?” Usually Pediatric Pearls is behind a paywall, but I’m going to post this to everyone - hoping it helps as many as possible.
The Basics
Paxlovid is an antiviral medication that received Emergency Use Approval (EUA) from the U.S. Food and Drug Administration (FDA) for those aged 12 and older with mild-to-moderate COVID-19 with positive results of direct viral testing and who are at high risk for progression to severe COVID-19.
Paxlovid is made by the pharmaceutical company, Pfizer.
Paxlovid is the brand name for the drug which is made up of two generic medications - nirmatrelvir and ritonavir. Paxlovid is produced by the pharmaceutical company, Pfizer.
The recommendation is to start Paxlovid within 5 days of developing symptoms. Paxlovid is taken by mouth – three Paxlovid pills twice a day for five days. Thus, a full course consists of 30 pills. The pills are packaged in a medication blister pack that allows you to punch out the pills as needed. The two separate medications are packaged together.
Nirmatrelvir and Ritonavir
In the three-pill dose, two of those pills are nirmatrelvir, the drug that inhibits the SARS-CoV-2 protein from replicating. The other pill is ritonavir, an antiretroviral medication traditionally used to treat HIV. Ritonavir enhances the bioavailability of nirmatrelvir by slowing its metabolism in the liver - so it stays in the body longer. (1)
How does Paxlovid work?
The drug (specifically nirmatrelvir) works by disrupting the replication of SARS-CoV-2 in the body by binding to the 3CL-like protease, an enzyme that plays a crucial role in the functioning and reproduction of the virus.
Is Paxlovid safe to take when breastfeeding?
Let’s try to answer this question by looking at two resources:
LactMed Update
Infant Risk Center
Note that because the amount of ritonavir that enters human milk is low (RID of .42%), this discussion is about the second drug in Paxlovid, nirmatrelvir.
LactMed Update
Philip O. Anderson wrote a LactMed Update which was published in Breastfeeding Medicine, the journal of the Academy of Breastfeeding Medicine. (2)
Dr. Anderson is Health Sciences Clinical Professor of Pharmacy at the Skaggs School of Pharmacy and Pharmaceutical Sciences. He is the founder of the LactMed data base which is a widely used site helping answer the question of safety of medications while breastfeeding.
In this article he writes, “The EUA for nirmatrelvir recommends weighing the benefits and risks of breastfeeding with the drug, which is a weaker warning than with molnupiravir (another medication with EUA) for treatment of COVID-19, and it appears to be based on a lack of safety data rather than any adverse reaction concern. Ritonavir has been studied in breastfeeding mothers being treated for HIV infection. It is excreted into milk in low concentrations, and low levels can be found in the blood of some breastfed infants. No adverse reactions in breastfed infants have been reported with ritonavir. Because of the poor oral bioavailability of nirmatrelvir and small amounts of ritonavir in milk, this combination is unlikely to adversely affect the nursing infant.” (2)
Infant Risk Center
Paxlovid is ranked as a L3 in the Infant Risk Center app. It reports limited data – probably compatible. The relative infant dose is 1.43%; the molecular weight is 499.
Here is what the Infant Risk Center app says: “No data is available on the transfer of nirmatrelvir into human milk. Due to modest protein binding and molecular weight, nirmatrelvir is only expected to transfer into milk transfer to a moderate degree…While it is not ideal for a breastfeeding mother, it is likely the benefit of treatment against COVID -19 may outweigh the infant risk of drug transfer with a short duration of therapy.” (3)
Based on these two resources, I’m concluding yes.
References
Kathy Katella. 13 Things to Know about Paxlovid, the Latest Covid-19 Pill. https://www.yalemedicine.org/news/13-things-to-know-paxlovid-covid-19
Anderson PO. Covid 19 Drugs and Breastfeeding Update. Breastfeed Med. 2022;17(5):1-3. https://www.liebertpub.com/doi/10.1089/BFM.2022.0066
Infant Risk Center Infant Risk Center