Breastfeeding and Human Lactation by Riordan and Auerbach and the Mother
Risk Clinic at Toronto's Hospital for Sick Children both agree that  the
tricyclic antidepressant desipramine is safe for nursing mothers.  Mother
Risk also says it is safe in pregnancy, from conception on.  I've seen a
mother use this and there were no observable side effects in the baby and
it worked well for the mother.