Lactating mothers often express concerns that drugs they take, or which are prescribe for them by a doctor, may be excreted in breast milk and may affect the baby. While most drugs, including antibiotics, do pass into breast milk, the amount is small and will neither benefit nor harm the baby.
Only a few drugs may cause damage to the baby. These include anticoagulants(given to the mother to treat blood clots) which may cause haemorrhages in the body; antithyroid drugs(particularly thiouracil) which may depress the infant's thyroid gland; ) a laxative called coloxyl which may give the baby diarrhoea; lithium which may make the baby cold and blue, and mysoline which is sometimes used to treat epilepsy.
If you have been prescribe one of these drugs, stop breastfeeding and ask your doctor if its safe to continue to breast feed......