There was an article discussing Breastfeeding and Anaesthesia published in 1993 which
discusses use of many analgesics and anaesthetic agents, and is well referenced.
The article is:
JJ Lee, AP Rubin 1993 Breastfeeding And Anaesthesia, Anaesthesia Vol 48 pages 616-625.
Hope this helps
Fiona Coombes
Perth Western Australia