My brother-in-law Dr Rhys Henning works as an accredited medical practitioner with the South Australian Health Commission as a methadone provider.

He tells me that the standard advice is that during pregnancy the methadone dose should be decreased to 20mg or less per day to reduce the chances of withdrawal in the baby. It is uncommon for babies exposed to less than this dose to have neonatal problems related to methadone exposure.

He also tells me that he is happy for a woman to breastfeed on up to 60 mg per day. Babies don't seem to have any problems with this dose.

If a woman requires more than 60 mg per day he still recommends that they continue to feed and monitors the baby for problems. The problems are sedation and constipation,  the former which will attenuate with time.

I was somewhat alarmed at the prolonged use of phenobarbital mentioned. An article by Alvin H Novack MD from the University of Washington Children's Hospital Medical Center published on the net stated " While Phenobarbital is the most effective treatment for non-narcotic addiction the disadvantages of using it for Neonatal Abstinence Syndrome (NAS) are of sufficient significance to consider it as a last resort. Phenobarbital has almost no effect on the G.I. symptoms of diarhoea and poor suck, two potential life-threatening aspects of NAS. Phenobarbital is not effective in treating the seizures caused by narcotic withdrawal. It is difficult to maintain the newborn in a therapeutic range without pushing the serum levels of phenobarbital to toxicity. Finally, the need to monitor serum levels adds a negative dimension to its use for treatment of NAS."
"The negative effects of phenobarbital on cognitive development is another deterrent, especially if treatment continues for more than a few weeks."

Laureen Lawlor-Smith
BMBS IBCLC
South Australia