Is Imdevimab safe while breastfeeding?

Summary of use during breastfeeding

The distribution of casirivimab and imdevimab was stopped in January of 2022 because of a lack of efficacy against SARS-CoV-2 variants. Imdevimab is a monoclonal antibody given together with casirivimab. 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. Because imdevimab 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]

Effects on the breastfed infant

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 milk supply

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

Levels in milk

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.

Alternatives LactMed lists

• Nirmatrelvir