No information is available on the use of mavacamten during breastfeeding. Because it is 97 to 98% plasma protein bound, the amount of mavacamten in milk is likely to be very low. If a mother requires mavacamten, it is not a reason to discontinue breastfeeding. Until more data become available, mavacamten should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant.