Casirivimab and Breastfeeding

Summary of use during lactation

The distribution of casirivimab and imdevimab was stopped in the US in January of 2022 because of a lack of efficacy against COVID-19 variants. Because casirivimab is a large protein molecule, the amount in milk is likely to be very low.[1] It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[2] Casirivimab is a monoclonal antibody given together with imdevimab. Both are directed against the SARS-CoV-2 virus that causes COVID-19. Casirivimab and imdevimab transiently increased anti-receptor-binding domain IgG titers in one woman.

Drug levels in milk and infant serum

Maternal Levels. Maternal Levels. A nursing mother received the Pfizer-BioNTech COVID-19 vaccine about 1.8 months postpartum followed by the second dose in the primary series. From 60 day postpartum, she had a poor IgG antibody response against the receptor binding domain to the vaccine compared to a matched control woman. At day 216 postpartum, she tested positive for SARS-CoV-2 and on day 222, she received an intravenous infusion of casirivimab 600 mg and imdevimab 600 mg. Her milk anti-receptor-binding domain IgG titers increased markedly before returning to her baseline at about 560 days postpartum.[3] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

An unvaccinated Japanese woman who was 36 weeks and 6 days pregnant developed COVID-19 and was given an intravenous dose of casirivimab and imdevimab (Ronapreve) for her COVID-19 infection. Her infant was born 5 days later and separated from her. Approximately 10 days after the dose, she began breastfeeding her infant. At 30 days of age, the infant was in good health.[4]

Effects on lactation and breastmilk

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

Alternative drugs to consider

Nirmatrelvir, Remdesevir

References

1. Stratigakis A, Paty D, Zou P, et al. A regression approach for assessing large molecular drug concentration in breast milk. Reprod Breed 2023;3:199-207. doi:10.1016/j.repbre.2023.10.003
2. Anderson PO. Monoclonal antibodies during breastfeeding. Breastfeed Med 2021;16:591-3.33956488 PubMed
3. Marshall NE, Blanton MB, Doratt BM, et al. Monoclonal antibody therapy of breastfeeding patient infected with SARS-CoV-2: A case report. Breastfeed Med 2023;18:626-30.37615569 PubMed
4. Ogawa E, Goto H, Ushimaru H, et al. Vaginal delivery after improvement in COVID-19 by monoclonal antibody treatment: A case report and literature review. J Infect Chemother 2022;28:982-6.35288022 PubMed