Ditropan-oxybutynin-is an anticholinergic used to provide antispasmodic
effects for ....involuntary bladder spasms and reduces urinary urgency and
frequency.  Used in children down to 5 yrs of age at 15 mg/day.  No data on
transfer into human milk available, but oxybutynin is a tertiary amine
which is poorly absorbed orally (only 6%).  Hale goes on to figure out that
infant would theoretically get  " < 2 micrograms/day, a dose that would be
clinically irrelevant to even a neonate."  Above is from Medications and
Mothers' Milk 1997, Thomas Hale, PhD.