Ellen,
I have not seen a formal study but at the hospital I work in I haven't
noticed a relationship with pitocin and late onset of milk,  I would be more
suspicious of the epidural.  On a personal note, I was augmented with Pitocin
with both of my children  the first one for 8 hours and the 2nd for 1.5
hours.  I had demerol with the first and an epidural withe the 2nd (i only
had the epidural for 1.5hours and my milk came in with bothe children 2 days
post-partum.

Caren Goldstein RNC IBCLC