Can breastfeeding help decrease or alleviate a newborn's symptom severity from withdrawals associated w/ 3rd trimester, high-dose RX Xanax (alprazolam) exposure?

Not good idea. While Xanax (alprazolam) does cross into breast milk, the keve l s can be very erratic and thus not a good plan for withdrawl. Otherwise, you are basically asking about keeping your newborn addicted to a controlled substance by passing him the med through your milk to "alleviate withdrawl". You are not alleviating withdrawl, you are keeping them addicted. Don't do it. Do withdrawl supervised in hospital.