Maybe not. As a general rule of thumb it is best to keep medication use to a minimum during pregnacy and lactation. Diltiazem was given a pregnancy category c rating because of potential problems in animal studies. When given to pregnant rabbits, mice, and rats, Diltiazem caused an increased risk of miscarriages and birth defects (especially skeletal problems). But animals are not always the same as humans.
Wouldn't recommend . Diltiazem is class c in pregnancy and is excreted in breast mild. See link below http://www.Drugs.Com/pregnancy/diltiazem.Html.
Yes. While i don't feel comfortable saying medications are "safe" during breastfeeding ("compatible" is better), based on limited data, the amounts of Diltiazem ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants. For any questions on medications and breastfeeding, lactmed is a great resource. Read more...