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Letermovir Pregnancy and Breastfeeding Warnings

Letermovir is also known as: Prevymis

Medically reviewed on January 10, 2018

Letermovir Pregnancy Warnings

Embryo-fetal developmental toxicity (including fetal malformations), decreased fetal body weight, and skeletal variations (due to maternal toxicity) were observed in rats exposed to drug concentrations 11 times the RHD. No embryo-fetal toxicities were observed in doses estimated at 3 times the RHD. In rabbits, developmental toxicities, including spontaneous abortion, increased post-implantation loss, and skeletal variations were observed at maternally toxic doses (approximately 2 times higher than the RHD). In pre/post-natal development studies, total litter loss due to stillbirth or possible maternal neglect was observed in 5 of 23 pregnant female rats dosed at approximately 2 times the RHD. In surviving offspring, slight developmental delays in vaginal opening and pinna unfolding were accompanied by reduced weight gain. No toxicity was observed at doses approximating human exposure at the RHD. There are no controlled data in human pregnancy.

Decreased fertility due to testicular toxicity was observed in male rats; there are no data on human fertility.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

Benefit should outweigh risk

US FDA pregnancy category: Not assigned

Risk Summary: No adequate human data are available to establish a pregnancy risk; animal data has shown development toxicities in doses that exceed human exposure at the recommended human dose (RHD).

See references

Letermovir Breastfeeding Warnings

In lactating rats, this drug was present in the milk and blood of nursing pups. It is unknown if this drug is present in human breast milk or affects human milk production.

Benefit should outweigh risk

Excreted into human milk: Unknown
Excreted into animal milk: Yes

Comments: The effects in the nursing infant are unknown.

See references

References for pregnancy information

  1. "Product Information. Prevymis (letermovir)." Merck & Company Inc, Whitehouse Station, NJ.

References for breastfeeding information

  1. "Product Information. Prevymis (letermovir)." Merck & Company Inc, Whitehouse Station, NJ.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.