I'd stop the medication for the duration of breast feeding. Diet pills are absolutely not recommended to any breast feeding mother. There are mainly advantages. In general, most physicians are advocates for breast feeding if tolerated by the mother. I am breast feeding my 3 week old infant.
Breast milk concentrates several drugs including most of the benzodiazepines.
Although there may he some differences, for clinical purposes these drugs are similar in their sedative ability and concentration in breast milk. Anxiety disorders are occasionally treated with beta- blockers, which are relatively safe and not addicting like the benzodiazepines. Other drugs like the SRI antidepressants are also used, but data on use in small children is lacking here. I saw in the literature that breast feeding is contraindicated while taking this medication. This drug inhibits platelets and may induce bleeding.