Vanzacaftor, Tezacaftor and Deutivacaftor

No information is available on milk or infant serum levels of vanzacaftor or deutivacaftor. Information from mother-infant pairs with elexacaftor, ivacaftor and tezacaftor indicates that tezacaftor has low levels in milk and infant serum. Deutivacaftor is a deuterated form of ivacaftor that has slower clearance, a longer half-life and greater maternal exposure. Anecdotal evidence indicates that these types of drugs in breastmilk may moderate cystic fibrosis in breastfed infants or interfere with diagnostic tests for cystic fibrosis. Transient mild elevations in bilirubin and liver enzymes (AST-ALT) during maternal therapy with elexacaftor, tezacaftor and ivacaftor have been reported and tend to normalize during continued breastfeeding. Until more data are available, monitoring of infant bilirubin and liver enzymes is advisable during breastfeeding with maternal elexacaftor, lumacaftor and ivacaftor therapy.[1,2] One expert panel recommends that if ALT-AST is between 2 and 5 times the normal level, breastfeeding may need to be reduced; if ALT-AST exceeds 5 times the normal level, complete cessation of breastfeeding may be required.[2] Congenital cataracts in breastfed infants have been reported in the infants of mothers who took the drugs during pregnancy. Examination of breastfed infants for cataracts has been recommended.[2,3] An ophthalmological examination using a slit lamp should be performed as early as possible, ideally at 3 months of age, to screen for any lens opacities, which would necessitate the suspension of breastfeeding. If breastfeeding is discontinued, it may be possible to resume once there is improvement in the liver enzyme or ophthalmological findings.[2]