My baby brother is 3 weeks old and refusing breast milk, is it okay to start using baby formula in a bottle?

INFANT FEEDING. I see mom is taking propranolol, carbamezipine and propylthiouracil. All these are l-2 drugs, means she can breastfeed without adverse effects to the baby. If baby refuses to nurse, mom can pump the milk with breast pump and feed baby in the bottle. If enough milk is not there, she can supplement with formula after breast milk. Best advise: talk to the pediatrician.