Summary of Use during Lactation

Nirmatrelvir is given in combination with ritonavir, which enhances its bioavailability. Minimal information is available on the use of nirmatrelvir during breastfeeding. Ritonavir is excreted into milk in measurable concentrations and low levels can be found in the blood of some breastfed infants. No reports of adverse reactions in breastfed infants have been reported. For more information, refer to the LactMed record on 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.[1,2] Breastfeeding is not contraindicated during nirmatrelvir-ritonavir therapy in the US and Canada, but cessation of breastfeeding during its use is recommended in Europe.[1] Until more data are available it should only be used with careful infant monitoring for adverse effects.

Drug Levels

Maternal Levels. Relevant published information was not found as of the revision date.

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

In a cross-sectional study of women who had COVID-19 and received nirmatrelvir in combination ritonavir, two women breastfed their infants. No adverse effects were reported in the infants.[3]

Effects on Lactation and Breastmilk

Relevant published information was not found as of the revision date.

Alternate Drugs to Consider

Remdesevir

References

1.

Chourasia P, Maringanti BS, Edwards-Fligner M, et al. Paxlovid (nirmatrelvir and ritonavir) use in pregnant and lactating woman: Current evidence and practice guidelines-a scoping review. Vaccines (Basel). 2023;11:107. [PMC free article: PMC9866309] [PubMed: 36679952]

2.

Anderson PO. COVID-19 drugs and breastfeeding update. Breastfeed Med. 2022;17:377–9. [PubMed: 35384717]

3.

Lin CY, Cassidy AG, Li L, et al. Nirmatrelvir-ritonavir (Paxlovid) for mild coronavirus disease 2019 (COVID-19) in pregnancy and lactation. Obstet Gynecol. 2023;141:957–60. [PMC free article: PMC10147578] [PubMed: 36928334]

Substance Name

Nirmatrelvir

CAS Registry Number

2628280-40-8

Drug Class

Breast Feeding

Lactation

Milk, Human

Antiviral Agents

Protease Inhibitors